Abstracts for - SKKUphysics.skku.ac.kr/symposium/ichn2012/book.pdf · Abstracts for International Conference on Heavy Electrons and Novel Quantum Phases with A3 Workshop Gyeongju

Abstracts for

International Conference on

Heavy Electrons and Novel Quantum Phases

(ICHN 2012)

with A3 Workshop

Gyeongju KyoYuk MunHwa HoeKwan

July 5 - 7, 2012

BK21 Physics Research Division

Sungkyunkwan University

Sponsors :

APTCP, A3 (NRF)

Sungkyunkwan University

The Korean Superconductivity Society

Scope of the Conference

The International Conference on Heavy Electrons and Novel Quantum Phases

(ICHN 2012), a satellite conference of ICM 2012, will be held in Gyeongju, Korea

during July 5-7, 2012. The scientific program will be held in conjunction with

Korean Superconducting Society (KSS) Regular Meeting and A3 Workshop.

Topics that will be covered in this conference include, but not limited to

- High Temperature Superconductivity

- Heavy Fermion Superconductivity

- Novel Electronic Phases

- Heavy Fermions

- Quantum Criticality

- New Developments

Conference Organizers

Yunkyu� Bang (Chonnam University, Korea)

Hanyong� Choi (Sungkyunkwan University, Korea)

Tuson� Park (Sungkyunkwan University, Korea)

Joe� D.� Thompson (Los Alamos National Laboratory, USA)

Local Committee

Kwang-Yong� Choi (Chung-Ang University, Korea)

Jungseek� Hwang (Sungkyunkwan University, Korea)

Daejoon� Kang (Sungkyunkwan University, Korea)

Jihoon� Shim (POSTECH, Korea)

Advisory Board

Andrea� Bianki� (Montreal University, Canada)

Elbert� Chia (NTU, Singapore)

X.� Dai (IOP, China)

Shin-ichi� Fujimori (SPRING8, Japan)

P.� Gegenwart (GWDG, Germany)

S.� A.� Grigera (University of St Andrews, UK)

Jung� Hoon� Han (Sungkyunkwan University, Korea)

Kenji� Ishida (Kyoto University, Japan)

Jeongsoo� Kang (Catholic University of Korea, Korea)

Keehoon� Kim (Seoul National University, Korea)

S.� Kirchner (Dresden, Germany)

Georg� Knebel� (CEA-Grenoble, France)

Jiunn-Yuan� Lin (National Chiao Tung University, Taiwan)

Zohar� Nussinov (Washington University, USA)

Pacoal� Jose� Giglio� Pagliuso (UNICAMP, Brazil)

Kwon� Park (KIAS, Korea)

Silke� Paschen� (Vienna University of Technology, Austria)

Filip� Ronning (Los Alamos National Laboratory, USA)

Shinji� Watanabe (Kyushu University, Japan)

In� Sang� Yang (Ewha Womans University, Korea)

Y.� K.� Yang (IOP, China)

Huiqiu� Yuan� (Zhejiang University, China)

ICHN 2012 & A3

ICHN2012 & A3 Time Table

New Bldg. D Hall

July 5 (Thu.) July 6 (Fri.) July 7 (Sat.)

09:00-09:40 Registration Plenary Talk 2 Plenary Talk 3

09:50-10:40 Fe-based SC I HF I Quantum Criticality

10:40-11:00 Tea Break

11:00-12:40 Fe-based SC II HF II New Developments

12:40-14:00 Lunch Closing Remarks

14:00-14:40 Plenary Talk 1Unconventional SC II

Excursion

15:00-15:50 Novel Phase

15:40-16:10 No Break Tea Break

16:00-16:40Unconventional SC I

Plenary Talk : KSS16:20-17:00

17:00-17:40Poster Session

17:40-18:20

18:30-20:00 Banquet

ICHN 2012 & A3

New Bldg. D Hall

Session : Plenary Talk 1

Chair : J. D. Thompson (LANL)

Plenay 01 (14:00-14:40, July 5)

The normal state of URu2Si2 : spectroscopic evidence for an anomalous Fermi

liquid.

Thomas� Timusk� (McMaster University, Canada)


Chair : H. Choi (Sungkyunkwan Univ.)

Plenay 02 (09:00-09:40, July 6)

Destruction of the Kondo effect at an antiferromagnetic quantum critical point

F.� Steglich� (Max Planck Institute for Chemical Physics of Solids, Germany)


Chair : H. Lee (POSTECH)

Plenay 03 (09:00-09:40, July 7)

Quantum singularities and Fermi surface

J.� Flouquet� (CEA Grenoble, France)

ICHN 2012 & A3

July 5 (Thu.), New Bldg. D Hall

Session : Fe-based SC I

Chair : S. Uchida (Univ. of Tokyo)

O-01 (09:50-10:15)

In-plane Resistivity Anisotropy of Underdoped BaFe2As2 with Various Chemical

Substitution

S.� Ishida� a,b,c,� M.� Nakajimaa,b,c,� T.� Lianga,b,c,� K.� Kihoua,c,� C.� H.� Leea,c,� A.� Iyoa,c,� H.�

Eisakia,c,� T.� Kakeshita

b,c,Y.� Tomioka

a,c,T.� Ito

a,c,� S.� Uchida

b,c (aNational Institute of

Industrial Science and Technology, Japan, bDepartment of Physics, University of

Tokyo, Japan, cJST, Transformative Research-Project on Iron Pnictides, Japan)

O-02 (10:15-10:40)

Phase diagram and Competition between superconductivity and

antiferromagnetism in AxFe2-ySe2 system

X.� H.� Chen (Hefei National Laboratory for Physical Sciences at Microscale and

Department of Physics, University of Science and Technology of China, China)

ICHN 2012 & A3


Session : Fe-based SC II

Chair : C. Kim (Yonsei Univ.)

O-03 (11:00-11:25)

Ab initio study of iron-based superconductors –Roles of electron correlations and

large Mott proximity-

Takahiro� Misawa (Department of Applied Physics, University of Tokyo, Japan)

O-04 (11:25-11:50)

Enhancement of the superconducting transition temperature from the competition

between electron-electron correlations and electron-phonon interactions

Rayda� Gammag1� and� Ki-Seok� Kim

2,3 (1Asia Pacific Center for Theoretical Physics,

POSTECH, Korea, 2Institute of Edge of Theoretical Science (IES), POSTECH, Korea, 3Department of Physics, POSTECH, Korea)

O-05 (11:50-12:15)

Anisotropic superconducting gap in the iron pnictide superconductor

BaFe2(As1-xPx)2T.� Yoshida1,2,*,� S.� Ideta1,� I.� Nishi1,� A.� Fujimori1,2,� T.� Shimojima3,� W.� Malaeb4,� S.�

Shin2,4

,� Y.� Nakashima5,� H.� Anzai

5,� A.Ino

2,5,M.� Arita

6,� H.� Namatame

6,� M.�

Taniguchi5,6

,� K.� Kumigashira7,� K.� Ono

7,� S.� Kasahara

8,� T.� Shibauchi

9,� T.� Terashima

8,�

Y.� Matsuda9,� M.� Nakajima1,� S.� Uchida1,2,� Y.� Tomioka2,10,� T.� Ito2,10,K.� Kihou2,10,� C.�

H.� Lee2,10

,� � A.� Iyo2,10

,� H.� Eisaki2,10

,� H.� Ikeda2,9

,and� R.� Arita2,3 (1Department of

Physics, University of Tokyo, Japan, 2JST-TRIP, Japan, 3Department of Applied Physics,

University of Tokyo, Japan, 4Institute for Solid State Physics, University of Tokyo,

Japan, 5Graduate School of Science, Hiroshima University, Japan, 6Hiroshima

Synchrotron Center, Hiroshima University, Japan, 7Photon Factory, Institute of

Materials Structure Science, KEK, Japan, 8Research Center for Low Temperature and

Materials Sciences, KyotoUniversity,J apan, 9Department of Physics, KyotoUniversity,

Japan, 10National Institute of Advanced Industrial Science and Technology, Japan)

O-06 (12:15-12:40)

Pressure driven quantum criticality and reemergence of superconductivity in iron

selenide superconductors

Liling� Sun� and� Zhongxian� Zhao (Institute of Physics and Beijing National Laboratory

for Condensed Matter Physics, Chinese Academy of Sciences, China)

ICHN 2012 & A3


Session : Novel Phase

Chair : K. Choi (Joongang Univ.)

O-07 (15:00-15:25)

Superconductivity Induced by Longituidinal Ferromagnetic Fluctuations in UCoGe

K.� Ishida1,� T.� Hattori

1,� Y.� Ihara

1,� Y.� Nakai

1,� Y.� Tada

1,� S.� Fujimoto

1,� N.� Kawakami

1,�

E.� Ozaki2,� K.� Deguchi

2,� N.� K.Sato

2,� and� I.� Satoh

3 (1Department of Physics, Graduate

School of Science, Kyoto University, Japan, 2Department of Physics, Graduate School

of Science, Nagoya University, Japan, 3Institute of Materials Research, Tohoku

University, Japan)

O-08 (15:25-15:50)

Comparative Studies of Doping-Dependent Scanning Tunneling Spectra in Cuprate

and Ferrous Superconductors

Nai-Chang� Yeh� (Department of Physics, California Institute of Technology, USA)

ICHN 2012 & A3


Session : Unconventional SC I

Chair : M. Dzero (Kent Univ.)

O-09 (16:00-16:25)

Specific Heat Discontinuity vs TcinAnnealed Ba(Fe1-xCox)2As2

G.� R.� Stewart,� J.� S.� Kim,� and� B.� D.� Faeth (Department of Physics, University of

Florida, USA)

O-10 (16:25-16:50)

Magnetic field-induced antiferromagnetism in superconducting CeCoIn5

Ilya� Vekhter (Louisiana� State� University,� USA)

O-11 (16:50-17:15)

The hidden order and magnetism in URu2Si2 : recent progress in the

determination of the electronic states

G.� Knebel1,� D.� Aoki

1,� E.� Hassinger

1,� V.� Taufour

1,� T.� D.� Matsuda

1,� L.� Malone

2,� I.�

Sheikin3,� A.� Palacio-Morales

1,� A.� Pourret

1,� and� J.� Flouquet

1

(1SPSMS, UMR-E CEA / UJF-Grenoble 1, INAC, France, 2LNCMI-T, UPR 3228

(CNRS-INSA-UJF-UPS), France, 3LNCMI-G, CNRS, France)

O-12 (17:15-17:40)

Order Parameters of Iron Selenide based supercondutors Revealed by the Specific

Heat

H.� D.� Yang1�

and� J.� -Y.� Lin2 (1Department of Physics, National Sun Yat-Sen

University, Taiwan, 2 Institute of Physics, National Chiao Tung University, Taiwan)

ICHN 2012 & A3

July 6 (Fri.), New Bldg. D Hall

Session : HF I

Chair : K. Kim (Seoul Nat. Univ.)

O-13 (09:50-10:15)

Dramatic changes of Fermi surface induced by a magnetic field inside the

antiferromagnetic phase of CeRhIn5

H.� Q.� Yuan (Department of Physics and Center for Correlated Matter, Zhejiang

University, China)

O-14 (10:15-10:40)

Heavy-fermion semiconductors with a twist

Maxim� Dzero (Department of Physics, Kent State University, USA)

Session : HF II

Chair : J. Kang (Catholic Univ.)

O-15 (11:00-11:25)

Heavy Fermion ARPES: Issues, Challenges and Examples*

J.� W.� Allen (Randall Laboratory, University of Michigan, USA)

O-16 (11:25-11:50)

Quantum critical spin liquid in frustrated magnets

Y.� Tokiwa1,� C.� Stingl1,� P.� Gegenwart1,� S.� L.� Bud'ko2,� J.� J.� Ishikawa3,� K.� Kimura3,

S.� Nakatsuji3,� P.� C.� Canfield

2 (1Physikalisches Institut, Georg-August-Universität

Göttingen, Germany, 2Ames Laboratory and Department of Physics, Iowa State,

University, USA, 3Institute for Solid State Physics, University of Tokyo, Japan)

O-17 (11:50-12:15)

Probing magnetic states in CeRu2Al2B by magnetic force microscopy

Jeehoon� Kim (Los Alamos National Laboratory, USA)

O-18 (12:15-12:40)

Correlated Electron State in Ce1-xYbxCoIn5 Stablized by Cooperative Valence

Fluctuations

Lei� Shu (Department of Physics, University of California, USA, Department of Physics,

Fudan University, China)

ICHN 2012 & A3

July 6 (Fri.), New Bldg. D Hall

Session : Unconventional SC II

Chair : I. Vekhter (Louisiana Univ.)

O-19 (14:00-14:25)

Electronic Liquid Crystal Correlations in the Pseudogap States of High Tc

Superconductors

Eun-Ah Kim (Cornell University, USA)

O-20 (14:25-14:50)

Hybridization gap and the hidden order in the heavy fermion Kondo lattice

URu2Si2W.� K.� Park

1,� P.� H.� Tobash

2,� F.� Ronning

2,� E.� D.� Bauer

2,J.� L.� Sarrao

2,� J.� D.�

Thompson,� and� L.� H.� Greene1 (1University of Illinois at Urbana-Champaign, USA, 2

Los Alamos National Laboratory, USA)

O-21 (14:50-15:15)

Spin and Orbital Flavors in Iron Pnictides: From Momentum Space to Real Space

and Back

Zlatko� Tesanovic (Institute for Quantum Matter, Johns Hopkins University, Baltimore,

USA)

O-22 (15:15-15:40)

Inhomogeneous high field phase of nearly Pauli-limited superconductor

Ryusuke� Ikeda,� Yuhki� Hatakeyama,� Ken-ichi� Hosoya (Department of Physics, Kyoto

University, Japan)

ICHN 2012 & A3

Session : New Developments

Chair : J. Hwang (Sungkyunkwan Univ.)

O-25 (11:00-11:25)

Quantum criticality of Ce3Pd20Si6S.� Paschen (Institute of Solid State Physics, Vienna University of Technology, Austria)

O-26 (11:25-11:50)

Evidence of Gap opening in superconducting FeSe above the structural distortion

Maw-Kuen� Wu (National Dong Hwa University, Institute of Physics, Academia Sinica,

Taiwan)

O-27 (11:50-12:15)

Numerical Investigations of Spontaneous Orbital Currents in the Three-Orbital

Emery-Hubbard Model

Cheng-Chien� Chen (Stanford Institute for Materials and Energy Science, SLAC

National Accelerator Laboratory, USA)

O-28 (12:15-12:40)

Chiral Orbital Angular Momentum in Non-centrosymmetric Band Structure

Jung� Hoon� Han (Sungkyunkwan University, Korea)

July 7 (Sat.), New Bldg. D Hall

Session : Quantum Criticality

Chair : H. Yuan (Zhejiang Univ.)

O-23 (09:50-10:15)

Unconventional Quantum Criticality in Heavy Electron Systems

Shinji� Watanabe (Faculty of Engineering, Kyushu Institute of Technology, Japan)

O-24 (10:15-10:40)

Field-induced quantum critical point and nodal superconductivity in the

heavy-fermion superconductor Ce2PdIn8

Shiyan� Li (Department of Physics, Fudan University, China)

ICHN 2012 & A3

July 6 (Fri.), Corridor

Session : Poster

Chair : Y. Bang (Chonnam Nat. Univ.) / D. Kang (SKKU)

/ S. Watanabe (Kyushu Univ.) / H. Eisaki (AIST)

P-01

Magnetic phase diagram of the new heavy fermion compound Ce2PtIn8 – a

single crystal study

Marie� Kratochvílová (Department of Condensed Matter Physics, Faculty of

Mathematics and Physics, Charles University in Prague, Czech Republic)

P-02

The Interplay of Heavy Electron and Valence Fluctuation of YbCu2Ge2 under High

Pressure

A.� Miyake1,� F.� Honda2,� T.� Watanuki3,� A.� Machida3,� K.� Simizu1,� R.� Settai4,� Y.� Ōnuki4(1KYOKUNGEN, Osaka University, Japan, 2Graduate School of Engineering Science,

Osaka University, Japan, 3Condensed Matter Science Division, JAEA, Japan, 4Graduate

School of Science, Osaka University, Japan)

P-03

Tuning the Properties of CeCoIn5 by Doping with Ru

M.� N.� Ou1,� K.� Gofryk

2,� R.� E.� Baumbach

2,� E.� D.� Bauer

2,� J.� D.� Thompson

2,� F.�

Ronning2,� Y.� Y.� Chen1,� J.� M.� Lawrence2 (1Institute of Physics, Academia Sinica,

Taipei, Taiwan, 2Los Alamos National Laboratory, USA)

P-04

Pressure effect on anisotropic electrical resistivity of Hg-doped heavy-fermion

CeRhIn5

S.� Seo,� E.D.� Bauer1,� J.D.� Thompson1,� T.� Park (Department of Physics, Sungkyunkwan

University, Korea, 1Los Alamos National Laboratory, USA)

P-05

Large elastic softening in heavy fermion superconductor Rh17S15

Shalamujiang� Simayi,� K.� Sakano,� Y.� Nakanishi,� M.� Yoshizawa,� R.� SettaiA,� Y.� ÔnukiA

(Iwate University, Japan, AOsaka University, Japan)

ICHN 2012 & A3


Session : Poster



P-06

Temperature dependent Kondo resonance bands in CeCoGe2: DFT+DMFT

approach

Hong� Chul� Choi1,� B.� I.� Min

2,� K.� Haule

3,� G.� Kotliar

3,� and� J.� H.� Shim

1,2 (1Department

of Chemistry, Pohang University of Science and Technology, Korea, 2Department of

Physics, Pohang University of Science and Technology, Korea, 3Department of Physics,

Rutgers University, USA)

P-07

Ferromagnetism in the Kondo lattice model

Robert� Peters� and� Norio� Kawakami (Department of Physics, Kyoto University, Japan)

P-08

High resolution angle-resolved photoemission spectroscopy study on Ba1-xKxFe2As2

Q.� Q.� Ge,� Y.� Zhang,� M.� Xu,� and� D.� L.� Feng* (Physics Department, Surface Physics

Laboratory (National key laboratory), and Advanced Materials Laboratory, Fudan

University, China)

P-09

Angle-resolved Photoemission Study of SrFe2(As0.65P0.35)2H.� Suzuki� a,� T.� Yoshidaa,� L.� C.� C.� AmbolodeIIa,� S.� Idetaa,� A.� Fujimoria,d,� H.�

Kumigashira�b,� K.� Ono

b,� T.� Kobayashi

c,� S.� Miyasaka

c,d,� S.� Tajima

c,d (aUniversity of

Tokyo, Japan, bKEK, Photon Factory, Japan, cOsaka University, Japan, dJST-TRIP, Japan)

P-10

Photoemission study of iron based superconductor Eu(Fe1-xRux)2As2

M.� Xia1,� Z.� R.� Ye1,� M.� Xu1,Q.� Q.� Ge1,� R.� Peng1,� W.� H.� Jiao2,� G.� H.� Cao2,� D.� W.�

Shen3,� D.� L.� Feng

1 (1State Key Laboratory of Surface Physics and Department of

Physics, Fudan University, China, 2Department of Physics, Zhejiang University, China, 3State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of

Microsystem and Information Technology, Chinese Academy of Sciences, China)

ICHN 2012 & A3


Session : Poster



P-11

Electronic structure of heavily hole-doped KFe2As2 revealed by angle-resolved

photoemission spectroscopy

J.� Jiang,� Y.� Zhang,� Z.� R.� Ye,� M.� Xu,� F.� Chen,� X.� P.� Shen,� B.� P.� Xie,� and� D.� L.�

Feng*� (Department of Physics, Applied Surface Physics State Key Laboratory, Fudan

University, Shanghai 200433, P. R. China)

P-12

Angle-resolved and resonance photoemission study of FeTe

L.� C.� C.� Ambolode� II1,� M.� Horio1,� H.� Suzuki1,� S.� Ideta1,� T.� Yoshida1,3,� A.� Fujimori1,3,�

K.� Ono2,� H.� Kumigashira

2,� L.� Liu

1,� M.� � Takahashi

1,� T.� Kakeshita

1,3,� S.� Uchida

1,3�

(1Department of Physics, University of Tokyo, Japan, 2Photon Factory, IMSS, KEK,

Japan, 3JST, TRIP, Japan)

P-13

Evolution of the charge dynamics with P substitution in BaFe2(As1-xPx)2

investigated by optical spectroscopy

M.� Nakajimaa,b,c,� T.� Tanakab,c,� K.� Kihoua,c,� C.� H.� Leea,c,� A.� Iyoa,c,� T.� Kakeshitab,c,� H.�

Eisakia,c,� and� S.� Uchida

b,c (aNational Institute of Advanced Industrial Science and

Technology, Tsukuba, Japan, bDepartment of Physics, University of Tokyo, Japan, cJST,

Transformative Research-Project on Iron-Pnictides, Japan)

P-14

Superconductivity and Magnetic Ordering of EuFe2(As0.7P0.3)2 under High Pressure

Shigeki� Tanaka1,� Atsushi� Miyake

1,� Tomoko� Kagayama

1,� Katsuya� Shimizu

1,� Jing� Guo

2,�

Genfu� Chen3,� Liling� Sun

2 (1KYOKUGEN, Osaka University, Japan, 2Institute of Physics

and Beijing National Laboratory for Condensed Matter Physics, Chinese Academy of

Sciences, China, 3Department of Physics, Renmen University of China, China)

P-15

Electronic structure and anisotropy of Sr2VO3FeAs superconductor.

Hyo� Seok� Ji� and� Ji� Hoon� Shim (Department of Chemistry, Pohang University of

Science and Technology (POSTECH), Korea)

ICHN 2012 & A3


Session : Poster



P-16

Phase diagram and calorimetric properties of NaFe1−xCoxAs

A.� F.� Wang,� X.� G.� Luo,� Y.� J.� Yan,� J.� J.� Ying,� Z.� J.� Xiang,� G.� J.� Ye,� P.� Cheng,� Z.� Y.�

Li,� W.� J.� Hu,� and� X.� H.� Chen* (Hefei National Laboratory for Physical Science at

Microscale and Department of Physics, University of Science and Technology of

China, China)

P-17

Evidence for nodeless superconducting gap in NaFe1-xCoxAs from low-

temperaturethermal conductivity measurements

S.� Y.� Zhou1,� X.� C.� Hong

1,� X.� Qiu

1,� B.� Y.� Pan

1,� Z.� Zhang

1,� X.� L.� Li

1,� W.� N.� Dong

1,�

A.� F.� Wang2,� X.� G.� Luo

2,� X.� H.� Chen

2,� and� S.� Y.� Li

1* (1State Key Laboratory of

Surface Physics, Department of Physics, and Laboratory of Advanced Materials, Fudan

University, China, 2Hefei National Laboratory for Physical Science at Microscale and


P-18

Fabrication of Potassium doped Iron-based superconducting thin films by pulsed

laser deposition system.

Nam� Hoon� Leea,� Young� Hoon� Oh

a,� W.� N.� Kang

a,* (BK21 Physics Division and

Department of Physics, Sungkyunkwan University, Korea)

P-19

Temperature and doping dependent cross-sectional analysis of Fourier-transform

scanning tunneling spectroscopy of cuprate superconductor

Jhinhwan� Lee,� Shyam� Mohan*,� Jimin� Kim*,� Seokhwan� Choi� and� Chanhee� Kim

(KAIST, Department of Physics, Korea)

P-20

Evidence for a pseudogap in ab-plane optical conductivity measurements and its

applications

Il� Ho� Jung� and� Jungseek� Hwang (Department of Physics, Sungkyunkwan University,

Korea)

ICHN 2012 & A3


Session : Poster



P-21

Absence of pseudogap in electron-doped T'-Pr1.2La0.7Ce0.1CuO4 revealed by

angle-resolved photoemission spectroscopy

M.� Horio1,� T.� Yoshida1,� H.� Suzuki1,� L.� C.� Ambolode1,� A.� Fujimori1,T.� Mizokawa2,� K.�

Ono3,� H.� Kumigashira

3,� Y.� Mori

4,� T.� Adachi

4,� Y.� Koike

4 (1Department of Physics,

University of Tokyo, Japan, 2Graduate School of Frontier Sciences, University of Tokyo,

Japan,3Photon Factory, Institute of Materials Structure Science, KEK, Japan,

4Department of Applied Physics, University of Tohoku, Japan)

P-22

The angle and frequency dependences of the self-energy induced by the spin

fluctuations for the cuprate superconductors

Seung� Hwan� Hong,� Han-Yong� Choi (Department of Physics, SungKyunKwan

University,Suwon, Korea)

P-23

Eliashberg function of the underdoped and overdoped Bi2212 superconductors

deduced from the high resolution laser ARPES intensity

Jin� Mo� Boka,� Han-Yong� Choia,Junfeng� Heb,� X.� J.� Zhoub,� C.� M.� Varmac (aDepartment

of Physics, SungKyunKwan University, Korea, bInstitute of Physics, Chinese Academy of

Sciences, China, cDepartment of Physics and Astronomy, University of California, USA)

P-24

Low-energy spin excitation in coexistent phase of antiferromagnetism and d-wave

superconductivity

Hyun-Jung� Lee*� and� Tetsuya� Takimoto** (*Korea Institute for Advanced Study,

Korea, **Asia Pacific Center for Theoretical Physics, Korea)

P-25

Interplay between superconductivity and nematic order

Eun-Gook� Moon (University of California, Santa Barbara, USA)

ICHN 2012 & A3


Session : Poster



P-26

Effects of spin fluctuations on critical behaviors of itinerant weak antiferromagnets

Rikio� Konno1,� Nobukuni� Hatayama1,� Yoshinori� Takahashi2

(1Kinki University Technical College, 2Graduate School of Material Sciences, University

of Hyogo, Japan)

P-27

Effects of substrate temperature on microstructure and superconducting

properties of MgB2 coated Hastelloy tapes

O.� Y.� Lee� a,� Mahipal� Ranota,� K.� H.� Choa,� W.� N.� Kanga,*,� S.� Ohb,� K.� C.� Chungc�

(aSungkyunkwan University, Korea, bNational Fusion Research Institute, Daejeon, Korea, cKorea Institute of Machinery and Materials, Korea)

P-28

Vortices perpendicular to an in-plane magnetic field in non-centrosymmetric

interface superconductors

Kazushi� Aoyamaa,b,c

� and� Manfred� Sigristb (aYoung Researcher Development Center,

Kyoto University, Japan, bInstitute for Theoretical Physics, ETH Zurich, Switzerland, cDepartment of Physics, Kyoto University, Japan)

P-29

Emergence of Chiral Orbital Angular Momentum and Circular Dichroism ARPES

Jin-Hong� Park1,� Choong� H.� Kim

2,� Jun-Won� Rhim

3,� and� Jung� Hoon� Han

1,4�

(1Department of Physics and BK21 Physics Research Division, Sungkyunkwan

University, Korea, 2Department of Physics and Astronomy, Seoul National University,

Korea, 3School of Physics, Korea Institute for Advanced Study, Korea, 4Asia Pacific

Center for Theoretical Physics, POSTECH, Korea)

P-30

Electronic State of 1D Iron-Selenide BaFe2Se3

T.� Kakeshita�a,� R.� Suzuki

a,� M.� Takahashi

a,� L.� Liu

a,� S.� Uchida

a,� K.� Kihou

b,� A.� Iyo

b,� H.�

Eisakib (aDepartment of Physics, University of Tokyo, Japan, bNational Institute of

Advanced Industrial Science and Technology (AIST), Japan)

ICHN 2012 & A3


Session : Poster



P-31

A Softening of Singlet Bound States in the Spin-Ladder like Compound BiCu2PO6

K.� Y.� Choi1,� J.� W.� Hwang

1,� P.� Lemmens

2,D.� Wulferding

2,� H.� Nojiri

3,� G.� -J.� Shu

4,�

and� F.� C.� Chou4 (1Department of Physics, Chung-Ang University, Korea, 2ICMP, TU

Braunschweig, Germany, 3IMR, Tohoku University, Japan, 4CCMS, National Taiwan

University, Taiwan)

P-32

Z2striped spin liquid in kagome spin ½ Heisenberg antiferromagnets

Michael� J.� Lawler (Binghamton University, USA)

P-33

Exotic phases in the frustrated hexagonal lattice

Daniel� C.� Cabra (Departamento de Física, Universidad Nacional de La Plata,

Argentine)

P-34

Enhanced Quasi-One-Dimensionality of SmNiC2 by Pressure and its Effect on

Charge Density Waves

Jae� Nyeong� Kim� and� Ji-Hoon� Shim (Department of Chemistry, Pohang University of

Science and Technology, Korea)

P-35

Correlation-Induced Non-Stoner type Metallic Ferromagnetism of One-Dimensional

Transition Metal Chains

Hanhim� Kang,� Geunsik� Lee,� P.� Dua,� Ji-Hoon� Shim,� and� Kwang� S.� Kim (Department

of Chemistry, Pohang University of Science and Technology, Korea)

P-36

Observation of orbital angular momentum from t2g-states of Sr2RuO4.

Wonsig� Jung1,� Wonshik� Kyung

1,� Beomyoung� Kim

1,Yoonyoung� Koh

1,� Chul� Kim

1,�

SoohyunCho1,� Masashi� Arita

3,� Kenya� Shimada

3,� Yoshida� Yoshiyuki

1�and�

Changyoung� Kim1,* (1Institute of Physics and Applied Physics, Yonsei University,

Korea, 2National Institute of Advanced Industrial Science and Technology (AIST),

Japan, 3Hiroshima Synchrotron Radiation Center, Hiroshima University, Japan)

ICHN 2012 & A3


Session : Poster



P-37

Phase diagrams and magnetic structures of R2RhIn8

Petr� Čermá (Charles University in Prague, Dept. of Condensed Matter Physics, Czech

Republic, Institute Laue Langevin, France)

P-38

Magnetic moment orderings of Fe atoms in Fe-intercalated TiX_{2} (X=S, Se)

Seung� Ill� Hyun� and� J.� h.� Shim (Department of Chemistry, POSTECH, Korea)

P-39

Observation of orbital angular momentum of topological insulator

Wonsig� Jung1,� Yeongkwan� Kim1,Beomyoung� Kim1,� Yoonyoung� Koh1,� Chul� Kim1,�

Masaharu� Matsunami2,� Shin-ichi� Kimura

2,� Masashi� Arita


3,� Jung�

Hoon� Han4,� Juyoung� Kim

5,� Beongki� Cho

5,� and� Changyoung� Kim

1,* (1Institute of

Physics and Applied Physics, Yonsei University, Korea, 2UVSOR Facility, Institute for

Molecular Science and Graduate University for Advanced Studies, Japan, 3Hiroshima

Synchrotron Radiation Center, Hiroshima University, Japan, 4Department of Physics,

Sungkyunkwan University, Korea, 5School of Physics and Department of Materials

Science and Engineering, GIST, Korea)

P-40

Edge State of the Topological Insulator in a Graphene Structure

Hyeonjin� Doh1� and� Gun� Sang� Jeon

2 (1Dept. of Physics, Konkuk University, Korea, 2

Dept. of Physics, Ewha Womans University, Korea)

P-41

Epitaxial graphene on heavily-ion-implanted 6H-SiC surfaces

J.� Seoa,� H.� Shin

a,� J.� Park

a,� J.� R.� Ahn

a,b (aBK21 Physics Research Division,

Sungkyunkwan University, Korea, bSKKU Advanced Institute of Technology (SAINT),

Sungkyunkwan University, Korea)

ICHN 2012 & A3


Session : Poster



P-42

Growth of epitaxial graphene on patterned SiC and transfer onto patterned

substrates.

Ji-Hoon� Park,� Hyeon-Jin� Shin,*� Jae-Young� Choi,� and� Joung� Real� Ahn* (BK21

Physics Research Division, Sungkyunkwan University, Korea)

P-43

Palladium silicidation and intercalation-induced epitaxial growth of charge neutral

quasi-free-standing monolayer graphene on a Si-face of 6H-SiC

Hacheol Shin, Inkyung Song, Chong-Yun Park, Joung Real Ahn (Sungkyunkwan

University, Republic of Korea)

P-44

Ru-doped La0.6Sr0.4MnO3 Thin Film as a Coercivity Tunable Material Studied by

X-ray Magnetic Circular Dichroism

T.� HaranoA,� K.� IshigamiB,� V.� K.� VermaA,� G.� ShibataA,� T.� KadonoA,� A.� FujimoriA,C,� K.�

TakedaC,� T.� Okane

C,� Y.� Saito

C,� H.� Yamagami

D,� H.� Yamada

E,� A.� Sawa

E,� M.�

KawasakiF,� Y.� Tokura

F,� A.� Tanaka

G

(ADepartment of Physics, Graduate School of Science, The University of Tokyo, Japan, BDepartment of Complexity Science and Engineering, Graduate School of Frontier

Sciences, The University of Tokyo, Japan, CQuantum Beam Science Directorate, Japan

Atomic Energy Agency (JAEA), Japan, DDepartment of Physics, Graduate School of

Science, Kyoto Sangyo University, Japan, ECorrelated Electron Heterointerfaces Group,

Nano electronics Research Institute, National Institute of Advanced Industrial Science

and Technology (AIST), Japan, FDepartment of Applied Physics, School of Engineering,

The University of Tokyo, Japan, GDepartment of Quantum Matter, Graduate School of

Advanced Sciences of Matter, Hiroshima University, Japan)

ICHN 2012 & A3


Session : Poster



P-45

Electrical and magnetic phase transition characteristics of VO2 thin flims grown

on GaN substrate

Hyoung� Woo� Yang1,� Junginn� Sohn

2,� Seung� Nam� Cha

2,� Jong� Min� Kim

2�and� Dae�

Joon� Kang1*

(1Department of Energy Science, BK21 Physics Research Division, Institute of Basic

Science, Sungkyunkwan University, Korea, 2Frontier Research Lab., Samsung Advanced

Institute of Technology, Korea)

P-46

Study on Cu2ZnSnS4 thin films prepared by Pulsed Laser Deposition method

Seokbae� Lee1,� Ilho� Jung

1,� Jongsung� Bae

2�and� Jungseek� Hwang

1

(1Department of Physics, Sungkyunkwan University, Korea, 2Busan Center, Korea Basic

Science Institute, Korea)P-47

Selective Band Engineering of an Isolated Subnanometer Wire

I.� Song,� D.� -H.� Oh,� C.� -Y.� Park,� and� J.� R.� Ahn (Sungkyunkwan University, Korea)

P-48

Orbital angular momentum structure of Cu(111) and Au(111) surface states.

Beomyoung� Kim1,� Choong� H.� Kim

2,� Panjin� Kim

1,� Wonsig� Jung

1,� Yeongkwan� Kim

1,�

Yoonyoung� Koh1,� Masashi� Arita


3,� Hirofumi� Namatame

3,� Masaki�

Taniguchi3,� Jaejun� Yu2,� and� Changyoung� Kim1,* (1Institute of Physics and Applied

Physics, Yonsei University, Korea, 2 Department of Physics and Astronomy, Seoul

National University, Korea, 3Hiroshima Synchrotron Radiation Center, Hiroshima

University, Japan)

P-49

Spontaneous-step-selective growth of In nanowires on Si(557): a ideal template to

one-dimensional electronic structures

B.� G.� Shin1,� M.� K.� Kim1,� D.� -H.� Oh1,� C.� -Y.� Park1,3,� and� J.� R.� Ahn1,4 (1BK21 Physics

Research Division, Sungkyunkwan University, Korea, 2College of Pharmacy, Chungnam

National University, Korea, 3Department of Energy Science, Sungkyunkwan University,

Korea, 4SKKU Advanced Institute of Technology, Sungkyunkwan University, Korea)

ICHN 2012 & A3


Session : Poster



P-50

Metamagnetic transition in Ca1-xSrxCo2As2 (x = 0 and 0.1) single crystals

G.� J.� Ye,� J.� J.� Ying,� Y.� J.� Yan,� A.� F.� Wang,� Z.� J.� Xiang,� P.� Cheng,� G.� J.� Ye,� and�

X.� H.� Chen* (Hefei National Laboratory for Physical Science at Microscale and


P-51

s-wave superconductivity in barium-doped phenanthrene as revealed by

specific-heat measurements

Peng� Cheng1,� Jianjun� Ying

1,� Xiangfeng� Wang

1,� Yajun� Yan

1,� Ziji� Xiang

1,� Xigang�

Luo1,� Zhe� Sun2,� and� Xianhui� Chen1 (1Hefei National Laboratory for Physical Science

at Microscale and Department of Physics, University of Science and Technology of

China, China, 2National Synchrotron Radiation Laboratory, University of Science and

Technology of China, China)

P-52

Suppression of superconductivity in the Perovskite-type blocking layered

(Ca4Al2O6)(Fe2(As1-xPx)2) superconductor

Akira� Iyo,� Parasharam� M.� Shirage,� Kunihiro� Kihou,� Nao� Takeshita,� Hiroshi� Eisaki

(National Institute of Advance Industrial Science and Technology (AIST), Japan)

P-53

Resonant APRES study of NiS2-xSex

Garam� Han1,� Y.� K.� Kim

1,Y.� Y.� Koh

1,� B.� Y.� Kim

1,W.� S.� Kyung

1,� Chul� Kim

1,� C.� Kim

1�

(1Institude of Physics and Applied Physics , Yonsei university, Korea)

Plenary 01

The normal state of URu2Si2: spectroscopic evidence for an anomalous Fermi liquid.∗

Thomas Timusk

McMaster University, Hamilton Ont. Canada

The Landau Fermi liquid, is recognized experimentally by an electrical resistivity that is

proportional to the square of the absolute temperature. Calculations show that, if electron-electron scattering dominates the electron lifetime, in a Landau Fermi liquid, the resistivity, ρ(T,ω) = A′(ω2 +bπ2T2) where b = 4. Using a novel optical technique we find that instead of the Fermi liquid value of 4, the coefficient b = 1.0 ± 0.1 in the normal state of the heavy Fermion metal URu2Si2. This unexpected result implies that the electrons are experiencing a novel scattering process. This scattering is intrinsic and we suggest that, above 17.5 K, the uranium f electrons do not hybridize with the free spd electrons to form a coherent Fermi liquid but instead act like a dense array of elastic impurities, interacting incoherently with the charge carriers. This behavior is not restricted to URu2Si2. Fermi liquid like states with b not equal to 4 have been observed in a number of disparate systems but the significance of this result has not been widely recognized. * Work done in collaboration with U. Nagel,T. Uleksin, T. Rõõm,R.P.S.M. Lobo, P. Lejay, C.C. Homes, J. Hall, A.W. Kinross, S. Purdy, T.J.S. Munsie, T.J. Williams, G.M. Luke.

Plenary 02

Destruction of the Kondo effect at an antiferromagnetic quantum critical point

F. Steglich

Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Str. 40, 01187 Dresden,

Germany

In this talk, combined heat- and charge-transport measurements on YbRh2Si2 across its antiferromagnetic quantum critical point (QCP) are discussed [1]. This QCP concurs with a T = 0 4f-selective Mott transition, as had been inferred from disparate temperature dependences of thermodynamic and electrical-transport properties [2], an abrupt Fermi-surface reconstruction [3, 4] and the vanishing of a quantum-critical energy scale [5]. Our recent low-T measurements of the electrical and thermal resistivity reveal a violation of the Wiedemann-Franz law at the QCP of YbRh2Si2, where the residual thermal resistivity is estimated to exceed the residual electrical resistivity by about 10 % [1]. This finding sheds new light on the break-up of composite Landau quasiparticles, due to inelastic scattering processes at T = 0 which invoke electronic quantum critical fluctuations. Work done in collaboration with H. Pfau, S. Hartmann, U. Stockert, P. Sun, S. Lausberg, M. Brando, S. Friedemann, C. Krellner, C. Geibel, S. Wirth, S. Kirchner, E. Abrahams and Q. Si References [1] H. Pfau et al., Nature 484, 493 (2012). [2] J. Custers et al., Nature 424, 524 (2003). [3] S. Paschen et al., Nature 432, 881 (2004). [4] S. Friedemann et al., Proc. Natl. Acad. Sci. USA 107, 14547 (2010). [5] P. Gegenwart et al., Science 315, 969 (2007).

Plenary 03

Quantum singularities and Fermi surface

J Flouquet *

INAC- CEA Grenoble France

Focus will be given on quantum singularities ( magnetism, valence , superconductivity ) which can be induced via pressure , doping and / or magnetic field and their link to Fermi surface topology . Special attention will be given on metamagnetism and field reentrant phenomena :

- Metamagnetism in nearly anfiferromagnetic (AF) system : example of CeRu2Si2 serie/ new figure of decoupling between first order metamagnetism and pseudometamagnetism

- In ferromagnetic ( FM ) material : metamagnetism and FM wing evidence of quantum critical end point on the UGe2 and UCoAl cases

- H reentrant superconductivity example of URhGe and UCoGe - Reentrant AF in superconducting phases : CeRhIn5/CeCoIn5

Microscopic probes such are neutron scattering , NMR or quantum oscillations experiments will be compared with macroscopic probe notably thermal transport , magnetization and calorimetry . Remarks will be given on the similarity and differences between ce , Yb and U systems

In collaboration with D Aoki , T Combier , G Knebel, , B Mounir , A Palacio , A Pourret , V Taufour (CEA) T Matsuda (JAEA) H Harima and H Kotegawa (Kobe University) W Knafo ( LCMI – Toulouse )

Oral 01

In-plane Resistivity Anisotropy of Underdoped BaFe2As2 with Various Chemical Substitution

S. Ishida a,b,c, M. Nakajima a,b,c, T. Liang a,b,c, K. Kihou a,c, C. H. Lee a,c, A. Iyo a,c,

H. Eisaki a,c, T. Kakeshita b,c, Y. Tomioka a,c, T. Ito a,c, S. Uchida b,c

a National Institute of Industrial Science and Technology, Tsukuba, Japan

b Department of Physics, University of Tokyo, Tokyo, Japan c JST, Transformative Research-Project on Iron Pnictides, Tokyo, Japan

Symmetry breaking is one of the central issues in the modern physics. In the case of the

iron-based superconductors, parent compounds show an antiferromagnetic/orthorhombic (AFO) phase transition, where the electronic state is essentially anisotropic within the basal planes. The anisotropic charge dynamics of the AFO phase is observed by transport measurements [1], optical measurements [2], angle-resolved photoemission spectroscopy (ARPES) [3], scanning tunneling spectroscopy (STS) [4], and so on. Extensive theoretical and experimental studies are under way, in order to understand its origin, as well as its relationship to the mechanism of high-Tc superconductivity,

In this study, we have investigated the detailed doping dependence of the in-plane resistivity anisotropy for the BaFe2As2-based compounds with three dopant variations; Ba(Fe1-xCox)2As2, BaFe2(As1-xPx)2, and Ba1-xKxFe2As2. In the case of Co doping, both the magnitude of the residual resistivity and the resistivity anisotropy are proportional to the Co concentration x. The results indicate that the resistivity anisotropy originates from the anisotropic impurity scattering induced by Co atoms, which is regarded as a fingerprint of the anomalous charge dynamics of the AFO phase. Notably, the tendency is not unique to the Co-doping, but also holds for the P- and K- doped case. The origin of the anisotropic impurity state will be discussed.

keywords : superconductivity, iron pnictides, transport properties [1] J.-H. Chu et al., "In-Plane Resistivity Anisotropy in as Underdoped Iron Arsenide

Superconductor", Science 329, 824 (2010). [2] A. Dusza et al., "Anisotropic charge dynamics in detwinned Ba(Fe1-xCox)2As2", Euro.

Phys. Lett. 93, 37002 (2011). [3] M. Yi et al., "Symmetry-breaking orbital anisotropy observed for detwinned Ba(Fe1-

xCox)2As2 above the spin density wave transition", Prc. Natl. Acad. Sci. USA 108, 6878 (2011).

[4] T.-M. Chuang et al., "Nematic Electronic Structure in the "Parent" State of the Iron-Based Superconductor Ca(Fe1-xCox)2As2", Science 327, 181 (2010).

Oral 02

Phase diagram and Competition between superconductivity and antiferromagnetism

in AxFe2-ySe2 system

X. H. Chen

Hefei National Laboratory for Physical Sciences at Microscale and Department of Physics, University of Science and Technology of China, Hefei, Anhui 230026, China

The correlation and competition between antiferromagnetism and superconductivity are one

of the most fundamental issues in high temperature superconductors. Superconductivity in high temperature cuprate superconductors arises from suppressing an antiferromagnetic (AFM) Mott insulator while in iron-pnictide superconductors arises from AFM semimetals and can coexist with AFM orders. Superconductivity at 32 K is always accompanied by AFM phase with Neel temperature as high as ~550 K and local moment of 3.3μB in iron-chalcogenide superconductors AxFe2-ySe2. A natural question is whether the superconductivity and AFM microscopically coexist, or arise from the phase separation. Such different scenario raises many intriguing debates because the microscopic coexistence of superconductivity and the AFM with such high TN will lead to a big challenge in theory. Here, we report that the superconducting transition temperature (TC) is enhanced from 32 K to 44 K by suppressing the long-range antiferromagnetic order in AxFe2-ySe2 system. It suggests that superconductivity and AFM order are correlated, and the separation of SC and AFM phase is mesoscopic rather than macroscopic, and Tc of the intrinsic superconducting phase is 44 K, rather than 32 K widely observed in AxFe2-ySe2 system. These results give direct evidence for that there exists a competition between superconductivity and AMF order and the superconductivity is suppressed by the long-range AFM order. These results give a hint to gain insight into a mechanism in the high temperature superconductivity.

Oral 0

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Oral 04

Enhancement of the superconducting transition

temperature from the competition between electron-electron correlations and electron-phonon interactions

Rayda Gammag1 and Ki-Seok Kim2,3

1 Asia Pacific Center for Theoretical Physics, Hogil Kim Memorial building 5th floor,

POSTECH, Hyoja-dong, Namgu, Pohang, Gyeongbuk 790-784, Korea 2 Institute of Edge of Theoretical Science (IES), Hogil Kim Memorial building 5th floor,

POSTECH, Hyoja-dong, Namgu, Pohang, Gyeongbuk 790-784, Korea 3 Department of Physics, POSTECH, Hyoja-dong, Namgu, Pohang, Gyeongbuk 790-784,

Korea

We uncover that the competition between electron-electron correlations and electron-phonon interactions gives rise to unexpectedly huge enhancement of the superconducting transition temperature, several hundreds percent larger (> 200 K) than that of the case when only one of the two is taken into account (~ 30 K). Our renormalization group analysis reveals an underlying universal structure for the enhancement of the critical temperature in Fermi surface instabilities, which turns out to be essentially identical to that of a recent study [Phys. Rev. Lett. 108, 046601 (2012)] on the enhancement of the Kondo temperature in the presence of Rashba spin-orbit interactions. We also discuss the stability of superconductivity against nonmagnetic randomness.

Oral 05

Anisotropic superconducting gap in the iron pnictide superconductor BaFe2(As1-xPx)2

T. Yoshida1,2,*, S. Ideta1, I. Nishi1, A. Fujimori1,2, T. Shimojima3, W. Malaeb4, S. Shin2,4 ,

Y. Nakashima5, H. Anzai5, A. Ino2,5, M. Arita6, H. Namatame6, M. Taniguchi5,6, K. Kumigashira7, K. Ono7, S. Kasahara8, T. Shibauchi9, T. Terashima8, Y. Matsuda9,

M. Nakajima1, S. Uchida1,2, Y. Tomioka2,10, T. Ito2,10, K. Kihou2,10, C. H. Lee2,10, A. Iyo2,10, H. Eisaki2,10, H. Ikeda2,9, and R. Arita2,3

1Department of Physics, University of Tokyo, Japan, 2 JST-TRIP, Japan, 3Department of

Applied Physics, University of Tokyo, Japan, 4Institute for Solid State Physics, University of Tokyo, Japan, 5Graduate School of Science, Hiroshima University, Japan, 6Hiroshima

Synchrotron Center, Hiroshima University, Japan, 7Photon Factory, Institute of Materials Structure Science, KEK, Japan, 8Research Center for Low Temperature and Materials Sciences, Kyoto University, Japan, 9Department of Physics, Kyoto University, Japan,

10National Institute of Advanced Industrial Science and Technology, Japan

E-mail address: [email protected]

Most of the experimental studies on the iron pnictide superconductors have so far indicated that the superconducting gap opens on the entire Fermi surfaces in contrast to the d-wave superconducting gap in the high-Tc cuprate superconductors. However, the isovalent-substituted system BaFe2(As1-xPx)2 shows signatures of superconducting gaps with line nodes [1]. According to the spin-fluctuation-mediated pairing mechanism, a line node in the superconducting gap may appear in the strongly warped hole Fermi surface [2]. A recent angle-resolved photoemission study (ARPES) [3] reported a line node in the outer hole Fermi surface around the Z point, which is consistent with the theoretical prediction [2]. However, this result is not consistent with the previous laser ARPES result [4], where Fermi-surface-independent gaps were observed around the Z point. In order to resolve the controversy, we have performed a systematic ARPES study of BaFe2(As1−xPx)2. In the present work, similar to the laser ARPES study [4], we have observed an isotropic gap opening on the outer hole Fermi surface. Furthermore, the energy gap opens even above Tc, indicating pseudogap behavior similar to the high-Tc cuprates. On the other hand, we have revealed a strongly anisotropic gap with deep gap minima in the inner electron Fermi surface, suggestive of line nodes. This result indicates that the origin of the nodal behavior in the thermal conductivity [1] is the anisotropic gap in the inner electron Femi surface rather than the outer hole Fermi surface. Reference [1] K. Hashimoto et al., Phys. Rev. B 81, 220501 (2010). [2] K. Suzuki, H. Usui, and K. Kuroki, J Phys. Soc. Jpn. 80, 013710 (2011). [3] Y. Zhang et al., Nature Phys. 8, 371 (2012). [4] T. Shimojima et al., Science 332, 564 (2011).

Oral 06

Pressure driven quantum criticality and reemergence of superconductivity in iron selenide superconductors

Liling Sun and Zhongxian Zhao

Institute of Physics and Beijing National Laboratory for Condensed Matter Physics, Chinese Academy of Sciences, Beijing 100190, China

Superconductivity has been thought to be closely related to the quantum critical transition

in many correlated electronic systems such as cuprates, heavy fermions, organic conductors and iron pnictides. The states of quantum phases are determined by the lattice, charge, orbital and spin degree of freedom in materials. These factors can be manipulated by control parameters including pressure, magnetic field, and chemical composition. Among these parameters, pressure is a clean way in tuning the lattice and the electronic properties. In this talk, we will report an experimental discovery of pressure-driven quantum criticality in the newly discovered iron-selenide superconductors M0.8FexSe2 (M=K, Rb, Tl substituted Rb) [1]. The results of in-situ high pressure resistance and structure measurements demonstrate transitions from the metallic Fermi liquid behavior to the non-Fermi liquid behavior and from the antiferromagnetism to the paramagnetism at a critical pressure. In extended high-pressure studies on these iron selenide superconductors, we find that the system investigated enters a new superconducting state above the critical pressure after elimination of its initial superconducting phase [2]. The maximum Tc of the second superconducting phase reached 48 K, higher than the maximum Tc of the first superconducting phase. We propose that the reemerging superconductivity in the studied samples should be driven by the quantum critically. [1] J. Guo, X. J. Chen, C. Zhang, J. G. Guo, X. L. Chen, Q. Wu, D. C. Gu, P. W. Gao, X. Dai,

L. H. Yang, H. K. Mao, L. L. Sun and Z. X. Zhao, Phys. Rev. Lett. 108, 197001(2012). [2] L. L. Sun, X. J. Chen, J. Guo, P. W. Gao, Q. Z. Huang, H. D. Wang, M. H. Fang, X. L.

Chen, G. F. Chen, Q. Wu, C. Zhang, D. C. Gu, X. L. Dong, L. Wang, K. Yang, A. G. Li, X. Dai, H-K. Mao and Z. X. Zhao, Nature 483, 67 (2012).

Oral 07

Superconductivity Induced by Longituidinal Ferromagnetic Fluctuations in UCoGe

K. Ishida1, T. Hattori1, Y. Ihara1, Y. Nakai1, Y. Tada1, S. Fujimoto1, N. Kawakami1, E.

Ozaki2, K. Deguchi2, N. K. Sato2, and I. Satoh3

1Department of Physics, Graduate School of Science, Kyoto University, Kyoto 606-8502 Japan

2Department of Physics, Graduate School of Science, Nagoya University, Nagoya 464-8602 Japan

3Institute of Materials Research, Tohoku University, Sendai, 980-8577, Japan

We report 59Co nuclear magnetic resonance (NMR) and nuclear quadrupole resonance (NQR) studies on the single crystalline ferromagnetic superconductor UCoGe, which exhibits ferromagnetic ordering at TCurie =2.5 K and superconductivity below TSuper = 0.57 K [1]. The internal magnetic field at the Co site originating from the ferromagnetic moments was detected from the 59Co-NQR measurements [2]. Temperature variation of the 59Co-NQR spectra shows that the NQR signals arising from the paramagnetic (PM) and ferromagnetic (FM) regions coexist between 1 and 2.7 K, but the PM signal was not observed below 0.9 K. This suggests that the FM transition possesses a first-order-like character, and that single-crystal UCoGe is in the homogeneous FM state throughout the sample below 0.9 K.

The nuclear spin-lattice relaxation rate (1/T1) measured at the FM NQR signal decreases below TSuper due to the opening of the superconducting (SC) gap, which gives unambiguous evidence for the microscopic coexistence of ferromagnetism and superconductivity in UCoGe.

We also synthesized a reference compound YCoGe without 5f electrons, which possesses the same crystal structure as UCoGe, and investigated its physical properties. Since YCoGe shows neither ferromagnetism nor superconductivity down to 0.5 K, it is thus considered that ferromagnetism and superconductivity observed in UCoGe originate from its U 5f electrons. In order to investigate the anisotropy of magnetic fluctuations and spin susceptibility from a microscopic view points, we have performed 59Co-NMR measurements. From the analysis of angular dependence of the NMR spectra, we have succeeded in determine the principal axis of electric field gradient at the Co site. This has enabled us to measure 1/T1 and Knight shift for each axis. The experimental results indicate that both static and dynamic susceptibilities are ferromagnetic with strong Ising anisotropy along the c axis [3].

In addition, from the angle-resolved NMR measurements, we found that the magnetic field along the c axis (H//c) strongly suppresses both the FM Ising-type fluctuations and superconductivity in the same way [4]. These results strongly suggest that the characteristic FM fluctuations tuned by H//c induce the unique superconductivity in UCoGe, which is anticipated to be a spin-triplet superconductor. [1] N. T. Huy et al., Phys. Rev. Lett. 99, 067006 (2007). [2] T. Ohta et al., J. Phys. Soc .Jpn. 79, 023707 (2010). [3] Y. Ihara et al., Phys. Rev. Lett. 105, 206403 (2010). [4] T. Hattori et al. Phys. Rev. Lett. 108, 066403 (2012).

Oral 08

Comparative Studies of Doping-Dependent Scanning Tunneling Spectra in Cuprate and Ferrous

Superconductors

Nai-Chang Yeh

Department of Physics, California Institute of Technology, Pasadena, CA 91125, USA

We report comparative studies of the doping-dependent quasiparticle low-energy excitations in cuprate and ferrous superconductors by means of cryogenic scanning tunneling spectroscopy. The samples investigated include under- and optimally doped YBa2Cu3O7− (Y-123), over-doped (Y1−xCax)Ba2Cu3O7− (Ca/Y-123), optimally doped Sr0.9La0.1CuO2 (La-112), and the “122” compounds Ba(Fe1−xCox)2As2 (Co-122).

In the case of cuprate superconductors at zero fields (H = 0), spatially homogeneous coherence peaks at energies = ±d flanked by spectral “shoulders” at ±eff are found in under and optimally doped Y-123, and the directional tunneling gap SC(k) is consistent with a pure dx2-y2 pairing symmetry so that SC(k) = d cos(2k), where k denotes the angle of the quasiparticle momentum k relative to the anti-node. On the other hand, for overdoped Ca/Y-123, the pairing potential becomes consistent with (dx2-y2+s)-wave pairing symmetry so that SC(k) = d cos(2k) + s. Moreover, s increases with increasing hole doping (p) whereas both (SC)max (d+s) and eff decreases with increasing p. In contrast, only a pair of spatially homogeneous peaks is seen in electron-type La-112 at ±eff. For H > 0, pseudogap (PG) features are revealed inside the vortices, with PG = [(eff)

2(SC)2]1/2 > SC in under- and optimally doped Y-123 and PG < SC in both heavily overdoped Ca/Y-123 and optimally doped La-112. These results suggest that the physical origin of PG is a competing order (CO) coexisting with superconductivity (SC) and that PG in the hole-type cuprates decreases with increasing p. The notion of COs coexisting with SC is further corroborated by Fourier transformation (FT) of the local density of states (LDOS) of Y-123, where two types of spectral peaks are identified: One type is associated with -dependent quasiparticle interference (QPI) wave-vectors, and the other is a set of -independent wave-vectors that may be attributed to COs and the (,) magnetic resonances.

For the multi-band Co-122 (with x = 0.06, 0.08, 0.12), two-gap superconductivity is observed for all doping levels at H = 0. The FT-LDOS spectra are consistent with a sign-changing s-wave (s) pairing symmetry and the presence of a charge density wave (CDW) that accompanies the spin density wave (SDW) in the SC state. Magnetic resonant modes associated with the inelastic scattering of quasiparticles are also identified for all doping levels, and are found to following a universal relationship with the SC gaps at all temperatures. In the case of H > 0, an intra-vortex pseudogap similar to that in the cuprate superconductors is found. Further, the spectral features associated with magnetic resonances are found to be enhanced by magnetic fields.

Our comparative studies suggest that the commonalities among the cuprate and the ferrous superconductors include the proximity to COs, antiferromagnetic spin fluctuations and magnetic resonances in the SC state, and the unconventional pairing symmetries with sign-changing order parameters on different parts of the Fermi surface.

Oral 09

Specific Heat Discontinuity vs Tc in Annealed

Ba(Fe1-xCox)2As2

G. R. Stewart, J. S. Kim, and B. D. Faeth

Physics, University of Florida, Gainesville, FL 32611-8440 USA

The low temperature specific heat of nine compositions spanning the entire superconducting phase diagram of annealed Ba(Fe1-xCox)2As2 single crystal samples was measured. The purpose of this work was to investigate the relative variation of C/Tc on both the underdoped, coexistent superconducting and magnetic part of the superconducting dome and on the non-coexistent overdoped side. This study reveals that, within a rather narrow error bar, values of C/Tc adjusted to 100% superconducting volume fractions in all samples varied Tc

with the same value of the exponent (2) over 60% of the superconducting dome (Tc/Tc

opt>0.4) around the optimal, maximum Tc concentration on both the under- and overdoped sides.

Oral 10

Magnetic field-induced antiferromagnetism in superconducting CeCoIn5

Ilya Vekhter

Louisiana State University, USA

Competition and coexistence of different orders is a central theme in the physics of

correlated electron systems. One example of such cohabitation is between antiferromagnetism and superconductivity in several families of unconventional superconductors. The case of heavy fermion CeCoIn5 has challenged our understanding since this is the only situation where antiferromagnetism appears under an applied magnetic field in the superconducting state, but vanishes as soon as superconductivity is suppressed. I will focus on this puzzle and present a theory for the emergence of antiferromagnetism in CeCoIn5. I will show that in Pauli-limited nodal superconductors nesting of the quasiparticle pockets induced by Zeeman pair breaking leads to incommensurate antiferromagnetic state. I will compare the predictions of the theory with the experimental data and discuss the magnetic structure of the coexistence state.

Oral 11

The hidden order and magnetism in URu2Si2 : recent progress in the determination of the electronic states

G. Knebel1, D. Aoki1, E. Hassinger1, V. Taufour1, T.D. Matsuda1, L. Malone2, I. Sheikin3,

A.Palacio-Morales1, A. Pourret1, and J. Flouquet1

1 SPSMS, UMR-E CEA / UJF-Grenoble 1, INAC, 38054 Grenoble, France 2 LNCMI-T, UPR 3228 (CNRS-INSA-UJF-UPS), 31400 Toulouse, France

3 LNCMI-G, CNRS, 38042 Grenoble, France

The electronic states of the low carrier heavy fermion compound URu2Si2 and the nature of the hidden order is still puzzling. In this presentation we will discuss our recent experiments of quantum oscillations at ambient pressure for magnetic fields up to 34 T. All main SdH branches named were observed for all the measured field-directions (H || [001] → [100], [100] → [110] and [001] → [110]), indicating that these are attributed to the closed Fermi surfaces with nearly spherical shapes. The angular dependence of the β branch indicates a four folded Fermi surface. An anomalous split of branch α was detected for the field along the basal plane, and the split immediately disappears by tilting the field to [001] direction, implying a fingerprint of the hidden order state. High field experiments reveal the complicated field-dependence of the SdH frequencies and the cyclotron masses due to the Zeeman spin-splitting associated with the Fermi surface reconstruction in the hidden order state with small carrier numbers. A new SdH branch named with large cyclotron mass of 25m0 was detected at high fields above 23T close to the hidden order instabilities. The change of the Fermi surface under field will also be discussed on the basis of recent experiments of Seebeck and Nernst effect along the c axis. The results will be compared to recent band structure calculations.

High pressure Shubnikov de Haas experiments will be reported for the field along the c and a axis. All main frequencies could be followed under high pressure. These experiments indicate only little change of the quantum oscillation frequencies while the effective masses of all orbits decrease monotonously with pressure. This strongly suggests that the Fermi surface of the hidden orders state and the antiferromagnetic state under high pressure are very similar.

Oral 12

Order Parameters of Iron Selenide based supercondutors Revealed by the Specific Heat

H. D. Yang1

and J.-Y. Lin2

1Department of Physics, National Sun Yat-Sen University, Kaohusiung 804, Taiwan 2 Institute of Physics, National Chiao Tung University, Hsinchu 30010, Taiwan

We have measured the low-temperature specific heat of FeSe single crystals with in-plane or out-of-plane magnetic fields. The symmetry of the order parameter and the mixed state will be discussed. The zero field specific heat can be well fit into a two-gap model with an isotropic s-wave and an extended s-wave, consistent with the very recent theoretical calculations. The mixed state data further confirm the existence of an isotropic and a very anisotropic order parameter. The case of KxFe1-ySe2 is rather different from that of FeSe. The results of KxFe1-ySe2 are discussed under the scenario of phase seperation.

Oral 13

Dramatic changes of Fermi surface induced by a magnetic field inside the antiferromagnetic phase of CeRhIn5

H. Q. Yuan

Department of Physics and Center for Correlated Matter, Zhejiang University

In this talk, we will present the experimental evidence of a magnetic field induced quantum phase transition in CeRhIn5 by measuring the ac specific heat and the de Hass van Alphen oscillations in a pulsed magnetic field up to 70T. We found that the antiferromagnetic transition eventually vanishes at a critical field of Hc~50T. Direct evidence is obtained for a sharp reconstruction of the Fermi surface as a function of magnetic field inside the antiferromagnetic state of CeRhIn5, suggesting an SDW-type quantum critical point. Our findings implicate multiple universality classes of quantum critical points in the field-pressure phase diagram of this compound, and suggest that robust superconductivity can be promoted by unconventional quantum criticality with fluctuating Fermi surfaces.

Work was done in collaboration with L. Jiao, T. Shang, J. L. Zhang, Y. Chen (ZJU), Y.

Kohama, M. Jaime, J. Singleton, E. Bauer, T. Park, Hanoh Lee, J. D. Thompson (LANL) , F. Steglich (MPI-CPfS/ZJU) and Qimiao Si (Rice U)

Oral 14

Heavy-fermion semiconductors with a twist

Maxim Dzero

Department of Physics, Kent State University

In my talk, I will discuss how the properties of the Kondo insulators change when the symmetry of the underlying crystal field multiplets is taken into account. Specifically, I will demonstrate that in a large class of crystal field configurations, Kondo insulators can develop a topological non-trivial ground state. Such topological Kondo insulators are adiabatically connected to non-interacting insulators with unphysically large spin-orbit coupling, and as such may be regarded as interaction-drive topological insulators. Lastly, I will discuss recent progress made in our understanding of semiconducting behavior in f-electron systems.

Oral 15

Heavy Fermion ARPES: Issues, Challenges and Examples*

J. W. Allen

Randall Laboratory, University of Michigan, Ann Arbor, MI 48104 USA

A pressing issue in heavy fermion physics that could in principle be well addressed by

angle resolved photoemission spectroscopy (ARPES) is the inclusion or not of f-electrons in the Fermi surface (FS) as material composition or temperature is varied. A closely related application would be the making of definitive tests of predicted electronic structures using density functional theory in the local density approximation (LDA) or using dynamic mean field theory (DMFT) coupled with LDA. In spite of great technical advances in the past decade ARPES is still very challenged in addressing such issues. The challenges include the low energy and temperature scales for the physics of interest, the three dimensional character of most heavy fermion materials, and the great proclivity for these materials to manifest surface states that obscure the bulk electronic structures. This talk will illustrate these issues and challenges with applications of ARPES to Ce1-xYbxCoIn5 and URu2Si2. A particular focus is the use of photon-energy dependent ARPES to obtain the bulk three dimensional electronic structures of these materials and the detailed comparison with LDA and LDA+DMFT calculations while taking careful account of the limitations and implications of experimental resolutions. * In collaboration with N. P. Butch, J. D. Denlinger, L. Dudy, K. Haule, M. Janoschek, B. J. Kim, Kyoo Kim, G. Kotliar, O. Krupin, M. B. Maple, P. M. Oppeneer, K. Rossnagel, J. L. Sarrao, L. Shu, and V. S. Zapf.

Oral 16

Quantum critical spin liquid in frustrated magnets

Y. Tokiwa1, C. Stingl1, P. Gegenwart1, S. L. Bud'ko2, J. J. Ishikawa3, K. Kimura3, S. Nakatsuji3, P. C. Canfield2

1 Physikalisches Institut,Georg-August-Universität Göttingen, 37077 Göttingen,Germany 2Ames Laboratory and Department of Physics, Iowa State, University, Ames, Iowa 50011,

USA 3Institute for Solid State Physics, University of Tokyo, Kashiwa 277-8581, Japan

It has recently been proposed that a suppression of magnetic order by frustration can lead to quantum critical point (QCP)[1,2]. In Pr2Ir2O7 and YbAgGe, Pr and Yb respectively form corner-sharing tetrahedra and quasi-Kagome lattice, leading to geometrical frustrations of 4-f magnetic moments. The former does not order magnetically down to a spin-glass temperature, 0.12K[3], although the RKKY interaction is estimated to be 20K, and the latter orders only below 1K[4], which is much smaller than the absolute value of Weiss temperature, 15K. These frustrated magnets might be close to frustration-induced QCPs. In this study, we have performed measurements of magnetocaloric effect (MCE), specific heat, C, and thermal expansion, α, to examine their possible quantum critical behaviors.

In Pr2Ir2O7, magnetic Grüneisen ratio, ΓH, derived from MCE, shows a divergence as temperature is decreased down to 0.4K, indicating its close vicinity to QCP. ΓH, C and α all show a weak anomaly around 0.4K. This may be an indication of quantum melting of spin ice into the theoretically predicted magnetic-smectic phase[5]. Scaling behavior of ΓH suggests a zero-field QCP. Proposed chiral spin liquid (cSL) state below 1.5K[6] is entirely covered by the scaling regime, indicating that the quantum critical fluctuations mediate the cSL state.

H-T phase diagram of YbAgGe is highly complex, containing a, b, c, d, e and paramagnetic phases[7]. For T0, magnetic field of 4.8T induces a metamagnetic transition between c- and d-phases. At this critical field, a new type of quantum critical end point (QCEP) was proposed through measurements of thermal expansion[7]. Here, the QCEP is originated from a local-moment spin-flop transition between c and d phases, instead of itinerant electron metagmagnetism, causing QCEPs in CeRu2Si2[8] and Sr3Ru2O7[9]. We observed a sign change in ΓH at 4.8T, an accumulation of entropy and scaling behavior of divergent ΓH, all consistent with the QCEP. A cross-over line from QCEP extends into the paramagnetic phase. In order to form a cross-over in a disordered state, the local moments need to retain the magnetic structures of c and d phases in short range, implying two spin liquid states across the cross-over line. [1] J. Custers et al., Phys. Rev. Lett. 104 186402 (2010) [2] Q. Si, Phys. Status Solidi B 247 476. (2010) [3] S. Nakatsuji et al., Phys. Rev. Lett. 96 087204 (2006) [4] S. L. Bud’ko, et al., Phys. Rev. B 69, 014415 (2004) [5] S. Onoda et al., Phys. Rev. Lett. 105 047201 (2010) [6] Y. Machida et al., Nature 463 210 (2010) [7] G. M. Schmiedeshoff et al., Phys. Rev. B 83, 180408 (2011) [8] F. Weickert, et al., Phys. Rev. B 81, 134438 (2010) [9] P. Gegenwart, et al., Phys. Rev. Lett. 96, 136402 (2006)

Oral 17

Probing magnetic states in CeRu2Al2B by magnetic force microscopy

Jeehoon Kim

Los Alamos National Laboratory

A variety of magnetic states including ferromagnetism (FM), antiferromagnetism (AFM),

and spin reorientation (SR), were recently observed in CeRu2Al2B, which are related to the unusual local moment behavior of the Ce ions.1 In this system, the emergence of varied magnetic configurations within a narrow span of a tuning parameter (e.g., T and H) suggests the possibility of quantum frustration due to competing interactions between the Ce ions, although geometrical frustration is not expected since this compound crystallizes in a tetragonal structure. In this talk, I will report the structure of the magnetic states, directly probed by magnetic force microscopy (MFM), in CeRu2Al2B as a function of field and temperature. Interestingly, we observed frustration-like behavior in the field-dependent MFM images, which is in stark contrast to corresponding field-dependent domain behavior in CeRu2Ga2B, which shows pure ferromagnetism. In this system, the ferromagnetic ground state varies with temperature and field, resulting in a variety of domain structures, such as stripe and bubble domains. These domains, within a narrow window of T and H, provide an avenue for magnetic device applications. As a demonstration, we will show a dramatic change of magnetic domains by vortices in a Nb/CeRu2Al2B hybrid. [1] R. E. Baumbach, H. Chudo, H. Yasuoka, F. Ronning, E. D. Bauer, and J. D. Thompson,

“CeRu2Al2B: A local moment 4f magnet with a complex T-H phase diagram,” Physical Review B 85, 094422 (2012).

Oral 18

Correlated Electron State in Ce1-xYbxCoIn5 Stablized by Cooperative Valence Fluctuations

Lei Shu

Department of Physics, University of California, San Diego, La Jolla, California 92093, USA

Department of Physics, Fudan University, Shanghai 200438, China

Heavy fermion superconductivity has continuously attracted broad scientific attention. One of the important issues in this study is the relationship between quantum criticality, non-Fermi-liquid behavior (NFL), and unconventional superconductivity. It is generally thought that critical fluctuations associated with a magnetic quantum critical point (QCP) can provide a mechanism for NFL behavior and unconventional superconductivity in a narrow “dome” around the QCP. However, the precise nature of the relationship between these phenomena remains to be understood, particularly since many compounds have been reported where the NFL behavior persists over an extended region of the phase diagram in the absence of any identifiable QCP. Recently, intermediate valence phenomena has been found in the heavy fermion superconductor system Ce1-xYbxCoIn5. X-ray diffraction, electrical resistivity, magnetic susceptibility, and specific heat measurements reveal that many of the characteristic features of the x = 0 correlated electron state are stable for 0 ≤ x ≤ 0.775, and that phase separation occurs for x > 0.775. The stability of the correlated electron state is apparently due to cooperative behavior of the Ce and Yb ions, involving their unstable valences. Low temperature NFL behavior is observed which varies with x, even though there is no readily identifiable quantum critical point. The NFL state is tuned by valence fluctuations. The strongly intermediate-valence state of Yb in Ce1-xYbxCoIn5 has has been inferred by a simple model under the assumptions that Kondo effects can be ignored and the Ce valence is essentially 3+. The results are in very good agreement with the values found from angle-resolved photoemission spectroscopy, extended x-ray absorption fine structure, and x-ray absorption near-edge structure measurements.

Oral 19

Electronic Liquid Crystal Correlations in the Pseudogap States of High Tc Superconductors

Eun-Ah Kim

Cornell University

The nature of pseudogap phase of cuprate oxides has been one of the most debated topic in

condensed matter physics. Recently, the peculiarities of the pseudogap states were beautifully captured by STM data on Bi2Sr2CaCu2O8+x in the form of an inhomogenious spatial pattern of density of states. From these pseudogap patterns, we constructed liquid crystalline order parameter fields to quantify the symmetry breaking features[1]. These fields reveal two properties of the pseudogap phase: it has a net anisotropy (nematic order) over at least 100 nm length scales; the stripe-like smectic order in the patterns impacts the nematic order locally at dislocations in the tripe pattern. Further, we could construct a Ginzburg-Landau free energy of nematic and smectic order parameter fields that is minimally allowed by symmetry and capture these two properties[2]. Our results point towards important role of oxygen sites for microscopic models and open up opportunities to investigate the role these properties of pseudogap states play in superconductivity of high Tc cuprates. [1] Lawler, Fujita et. al., Nature 466, 347 (2010). [2] Mesaros, Fujita et. al., to appear in Science (2011)

Oral 20

Hybridization gap and the hidden order in the heavy fermion Kondo lattice URu2Si2

W. K. Park1, P. H. Tobash2, F. Ronning2, E. D. Bauer2, J. L. Sarrao2, J. D. Thompson,

and L. H. Greene1

1 University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA 2 Los Alamos National Laboratory, Los Alamos, NM 87545, USA

What drives the second order phase transition that occurs at 17.5 K in the Kondo lattice

heavy fermion URu2Si2 remains unknown after two and half decades of research despite ubiquitous observation of gap-like behaviors. Determining the nature of the extracted gaps, whether they are the long-sought order parameter or not, is a crucial task to resolving this hidden order enigma. Quasiparticle scattering spectroscopy (QPS), better known as point-contact spectroscopy, is a powerful technique to probe the bulk electronic properties by exploiting a ballistic junction between two metal electrodes. Employing QPS, we have carried out conductance measurements on URu2Si2 [1]. The differential conductance data exhibit a distinct double-peak structure with pronounced asymmetry, a signature for a Fano resonance in a Kondo lattice as predicted theoretically [2]. The extracted gap, a hybridization gap between the renormalized bands, opens well above the hidden order transition temperature, indicating this hybridization gap is not the hidden order parameter. Our results place severe constraints on the origin of the hidden order transition in URu2Si2. The work at UIUC is supported by the U.S. DOE under Award No. DE-FG02-07ER46453. The work at LANL is carried out under the auspices of the U.S. DOE, Office of Science. [1] W. K. Park et al., Phys. Rev. Lett. (in press). [2] M. Maltseva, M. Dzero, P. Coleman,

Phys. Rev. Lett. 103, 206402 (2009).

Oral 21

Spin and Orbital Flavors in Iron Pnictides: From Momentum Space to Real Space and Back

Zlatko Tesanovic

Institute for Quantum Matter, Johns Hopkins University, Baltimore, USA

The iron-pnictide high-temperature superconductors exhibit a more moderate degree of

correlations than their cuprate – or even iron-chalcogenide – relatives. This makes the itinerant description a reasonable starting point. However, with five iron d-orbitals and multiple electron and hole bands in play, the key challenge is to devise a relatively simple model that can capture the essential physics of these complex materials. I describe one such theoretical model, based on the approximate U(4)xU(4) symmetry of spin and band (orbital) degrees of freedom1. Several experimental predictions of the theory will be discussed with particular emphasis placed on the dimer resonances observed by STM. It will be argued that such resonances can serve as a diagnostic tool for various forms of density-wave ordered states in parent iron-pnictides1. 1J. Kang and Z. Tesanovic, Phys. Rev. B 83, 020505(R) (2011); J. Kang and Z. Tesanovic, http://arxiv.org/abs/1205.5280, to appear in Phys. Rev. B.

Oral 22

Inhomogeneous high field phase of nearly Pauli-limited superconductor

Ryusuke Ikeda, Yuhki Hatakeyama, Ken-ichi Hosoya

Department of Physics, Kyoto University, Kyoto 606-8502, Japan

Since 2003, the heavy fermion superconductor CeCoIn5 in high fields has continued to

show strange behaviors in its phase diagram: This compound has a peculiar high field and low temperature (HFLT) phase and suggests the presence of an antiferromagnetic (AFM) quantum critical point (QCP) just below Hc2(0) [1]. Further, neutron scattering data have definitely shown the presence of an AFM order in the HFLT phase [2]. Based on the strong Pauli paramagnetic pair-breaking (PPB) effect in this material suggested from the experimental Hc2(T)-curve, it is natural to ascribe the origin of those high field properties to PPB. In fact, it has been clarified [3] that the PPB, which is more effective in higher fields, induecs coexistence of superconducting (SC) and AFM orders in systems with the dx2-y2

pairing. On the other hands, the unusually strong impurity effect [4,5] has clarified that the HFLT phase does not consist of a homogeneous coexistence of SC and AFM orders but must include another spatially inhomogeneous modulation of the SC order parameter besides the vortex lattice structure. By taking account of the strong PPB in CeCoIn5, the most natural candidate among such modulations is that of the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state [1,3].

Here, besides a summary of researches on this subject performed so far, two recent results of our study on the HFLT phase of CeCoIn5 will be reported based on the picture [3] identifying the HFLT phase with a coexistent phase of the FFLO and AFM orders. First, the structure in real space of the AFM order is examined within the weak-coupling model, and the relative configuration between the two order parameters continuously changes with increasing the magnetic field in the lower half of the field range of the HFLT phase. In fact, recent NMR data [6] have suggested a continuous field-dependent change of the AFM order in real space. Second, a preliminary result on the resulting phase diagram within the strong-coupling model (Hubbard model in the FLEX approximation) is presented to show that the PPB-induced AFM ordering in the dx2-y2 paired superconducting phase is enhanced by the strong correlation. This result on how the AFM order appears is opposite with that seen in a previous study [7]. [1] A. Bianchi, Phys. Rev. Lett. 91, 187004 (2003). [2] M. Kenzelmann et al., Science 321, 1652 (2008). [3] R. Ikeda et al., Phys. Rev. B 82, 060510(R) (2010). [4] Y. Tokiwa et al., Phys. Rev. B 82, 220502(R) (2010). [5] R. Ikeda, Phys. Rev. B 81, 060510(R) (2010). [6] K. Kumagai, private communication. [7] Y. Yanase, J. Phys. Soc. Jpn. 77, 063705 (2008).

Oral 23

Unconventional Quantum Criticality in Heavy Electron Systems

Shinji Watanabe

Faculty of Engineering, Kyushu Institute of Technology, Kitakyushu, Fukuoka 804-8550,

Japan

We discuss the origin of unconventional criticality commonly observed in heavy electron metals [1]. We show that unconventional criticality emerges near the quantum critical end point of the first order valence transition (QCEP-FOVT) of Ce or Yb ion. By constructing a mode-coupling theory of critical valence fluctuations taking account of local correlation effects of f electrons, we find that unconventional criticality is caused by the locality of the valence-fluctuation mode. We show that low-temperature anomalies such as divergence of uniform spin susceptibility ~ T - and NMR/NQR relaxation rate 1/(T1T) ~ T - with ~0.6 and specific heat Ce/T ~ -logT, giving rise to a huge enhancement of the Wilson ratio, and emergence of T-linear resistivity appear near the QCEP-FOVT [2].

In the presentation, we discuss that proximity of the QCEP-FOVT is a key origin of several anomalies in Ce- and Yb-based heavy-electron systems: Unconventional criticality commonly observed in YbAlB4, YbRh2Si2 and YbCu5-xAlx [1,2,3], field-induced QCEP-FOVT giving rise to metamagnetism in CeIrIn5 and YbAgCu4 [4], and drastic change of Fermi surfaces as well as transport anomalies in CeRhIn5 [5]. Closeness to the QCEP-FOVT offers a key concept for understanding the new type of quantum criticality observed in some Ce- and Yb-based heavy-electron systems. [1] S. Watanabe and K. Miyake, J. Phys.: Condens. Matter 23 (2011) 094217. [2] S. Watanabe and K. Miyake, Phys. Rev. Lett. 105 (2010) 186403. [3] S. Watanabe and K. Miyake, in manuscript preparation. [3] S. Watanabe and K. Miyake, Phys. Status Solidi B 247 (2010) 490. [4] S. Watanabe et al., Phys. Rev. Lett. 100 (2008) 236401; J. Phys. Soc. Jpn. 78 (2009)

104706. [5] S. Watanabe and K. Miyake, J. Phys. Soc. Jpn. 79 (2010) 033707.

Oral 24

Field-induced quantum critical point and nodal superconductivity in the heavy-fermion superconductor

Ce2PdIn8

Shiyan Li

Department of Physics, Fudan University, Shanghai 200433, China

The in-plane resistivity and thermal conductivity of the heavy-fermion superconductor Ce2PdIn8 single crystals were measured down to 50 mK. A field-induced quantum critical point, occurring at the upper critical field Hc2, is demonstrated from the (T) ~ T near Hc2 and (T) ~ T2 when further increasing the field. The large residual linear term 0/T at zero field and the rapid increase of (H)/T at low field give evidence for nodal superconductivity in Ce2PdIn8. The jump of (H)/T near Hc2 suggests a first-order-like phase transition at low temperature. These results mimic the features of the famous CeCoIn5 superconductor, implying that Ce2PdIn8 may be another interesting compound to investigate for the interplay between magnetism and superconductivity.

Oral 25

Quantum criticality of Ce3Pd20Si6

S. Paschen

Institute of Solid State Physics, Vienna University of Technology, Wiedner Hauptstr. 8-10, 1040 Vienna, Austria

Ce3Pd20Si6 is a new heavy fermion compound that has recently attracted interest due to the

existence of a magnetic field induced quantum critical point. It crystallizes in the cubic Fm3m structure, with two distinct Ce sites. Ce moments at these two sites are held responsible for the occurrence of two consecutive phase transitions at low temperatures, a presumed antiferro -quadrupolar (AFQ) transition at TQ ≈ 0.5 K, and an antiferromagnetic (AFM) transition at TN ≈ 0.4 K. The latter has recently been confirmed by neutron diffraction [1]. Application of magnetic fields suppresses TN to zero at a field of about 0.9 T. TQ is first stabilized by the field and a complete suppression of the AFQ phase requires fields above 10 T.

The talk will focus on the nature of the quantum critical point (QCP) reached in Ce3Pd20Si6 as TN is suppressed to zero by magnetic field. We are thus studying the interesting case where a QCP is observed within another ordered phase. According to theoretical considerations, this AFQ phase should have a field-induced magnetic dipolar component [2]. Both within and outside the AFQ phase characteristics of a Kondo destruction energy scale T* that vanishes at the QCP are observed [2]. Thus, a Kondo destruction QCP appears to separate a magnetic phase with small Fermi volume from another magnetic phase with large Fermi volume. On theoretical grounds [3] such a situation is expected to occur at low values of the magnetic frustration parameter G, as function of the Kondo coupling JK. Thus, Ce3Pd20Si6 is an important experimental anchoring point of this barely explored region of the global G-JK phase diagram [2]. We gratefully acknowledge financial support from the European Research Council/ERC Advanced Grant No 227378. [1] P. P. Deen, K. A. Lorenzer, J.-M. Mignot, A. Prokofiev, A. Strydom, and S. Paschen,

unpublished. [2] J. Custers et al., Nature Materials 11, 189 (2012). [3] Q. Si, Physica B 378-380, 23 (2006).

Oral 26

Evidence of Gap opening in superconducting FeSe above the structural distortion

Maw-Kuen Wu

National Dong Hwa University, Hualien, 94701, Taiwan Institute of Physics, Academia Sinica, Taipei 11529, Taiwan

Detailed transport measurements including resistivity, thermoelectric power and Hall effects on FeSe suggest the modification of electronic structure at a temperature slightly above the structural distortion temperature. More recently, we utilize steady-state and transient optical spectroscopies to examine the responses of nonthermal quasiparticles with respect to orbital modifications in normal-state FeSe superconductor. The dynamics shows the emergence of gap-like quasiparticles with a coincident transfer of the optical spectral weight in the visible range at a temperature above the structural distortion. The temperature at which the anomalous optical response appears coincides with the temperature where the transport anomalies occur. Our observations suggest that opening of the high-temperature gap and the lattice symmetry breaking are possibly driven by short-range orbital and/or charge orders, implicating a close correlation between electronic nematicity and precursor order in FeSe superconductor.

Oral 27

Numerical Investigations of Spontaneous Orbital Currents in the Three-Orbital Emery-Hubbard Model

Cheng-Chien Chen

Stanford Institute for Materials and Energy Science, SLAC National Accelerator Laboratory,

Menlo Park, CA 94025, USA

Recent experiments show that the pseudogap regime of the cuprate superconductors could be characterized by a phase where the time-reversal symmetry is spontaneously broken but the translational symmetry remains intact. One possible but still highly disputed theory involves a spontaneous orbital current circulating around the copper and oxygen atoms. To address this issue, we perform large-scale exact diagonalization using the three-orbital Emery-Hubbard model. We find that the current-current correlations fall off quickly and show no signs of particular orbital current patterns. The strength of the correlation functions can be enhanced with a decreasing oxygen site energy, and/or with an increasing copper-oxygen Coulomb repulsion. Therefore, we also compute the cross sections of various photon-spectroscopies and benchmark the results with experiments in order to constrain the parameters that enter the calculations of the model Hamiltonian.

Oral 28

Chiral Orbital Angular Momentum in Non-centrosymmetric Band Structure

Jung Hoon Han

Sungkyunkwan University, Korea

We show, by way of tight-binding and first-principles calculations, that a one-to-one

correspondence between an electron’s crystal momentum k and nonzero orbital angular momentum (OAM) is a generic feature of surface bands. The OAMforms a chiral structure in momentum space much as its spin counterpart in Rashba model does, as a consequence of the inherent inversion symmetry breaking at the surface but not of spin-orbit interaction. This is the orbital counterpart of conventional Rashba effect and may be called the “orbital Rashba effect.” The circular dichroism (CD) angle-resolved photoemission (ARPES) method is an efficient way to detect this new order, and we derive formulas explicitly relating the CD-ARPES signal to the existence of OAM in the band structure. The cases of degenerate p- and d-orbital bands are considered.

Poster 01

Magnetic phase diagram of the new heavy fermion compound Ce2PtIn8 – a single crystal study

Marie Kratochvílová

Department of Condensed Matter Physics, Faculty of Mathematics and Physics, Charles

University in Prague

CenTmIn3n+2m (n=1, 2; m=1; T=transition metal) are attracting widespread interest in the field of condensed matter research. By adding an additional CeIn3-stacking layer the dimensionality changes from 3D to more 2D. While selecting the proper transition metal, the compound might either order antiferromagnetically or becomes superconducting. It has been shown, that the superconducting state is closely linked to the presence of a quantum critical point. These properties catapult this family of compounds to systems par excellence to investigate the interplay between SC and magnetism.

Recently, two new compounds from the CenTmIn3n+2m heavy fermion family have been found. Ce2PdIn8 is an ambient pressure superconductor while CePt2In7 orders antiferromagnetically.

Here, we report on the existence of a new heavy fermion (γ~370 mJ/molCe.K2) compound Ce2PtIn8. Similar to Ce2PdIn8, the synthesis of Ce2PtIn8 is rather complicated. However, from our recent studies of solution growth of Ce2PdIn8 supported by differential thermal analysis optimal conditions for growing Ce2PtIn8, single crystals could be deduced. Single crystal X-ray diffraction confirmed that Ce2PtIn8 crystallizes in Ho2CoGa8-type structure with lattice parameters a=4.699 Å and c=12.185 Å.

We will present specific heat, resistivity (ambient and under hydrostatic pressure) and magnetization measurements. Ce2PtIn8 orders magnetically below 2.1 K. A second, magnetic order-to-order transition is observed just below at 2 K. Contrary to Ce2RhIn8, both transitions merge at magnetic field around 4 T and split again in higher magnetic fields showing on different character of magnetic ordering. The magnetic field-temperature phase diagram will be discussed within the scope of evolution of SC and magnetism in related compounds.

Poster 02

The Interplay of Heavy Electron and Valence Fluctuation of YbCu2Ge2 under High Pressure

A. Miyake1, F. Honda2, T. Watanuki3, A. Machida3, K. Simizu1, R. Settai4, Y. O_

nuki4

1 KYOKUNGEN, Osaka University, Japan,

2 Graduate School of Engineering Science, Osaka University, Japan, 3 Condensed Matter Science Division, JAEA, Japan,

4 Graduate School of Science, Osaka University, Japan

YbCu2Si2 is well known as a typical valence fluctuating paramagnetic heavy fermion system with Yb2.8+ configuration and an electronic specific heat coefficient = 150 mJ/(K2 mol) [1]. Pressure-induced ferromagnetic ordering has been confirmed above ~8 GPa [2]. In contrast to YbCu2Si2, the isostructural compound YbCu2Ge2 having the ~10% larger unit cell than that of YbCu2Si2 seems to have nearly divalent configuration, e.g. typical metallic resistivity, small effective mass = 10 mJ/(K2 mol), and Pauli paramagnetic susceptibility [1]. For Yb-compounds, pressure often changes Yb-valence to be more trivalent configuration, and thus magnetic ground state. Here, we have investigated the interplay of heavy electrons and valence fluctuation in YbCu2Ge2 with tuning the Yb-valence widely by the external pressure. The electrical resistivity () and the Yb L2-edge XANES experiments have been performed under very high pressures up to 30 GPa. Temperature dependence of the resistivity (T) shows a typical metallic behavior at low pressures, which is expected for the non-magnetic compound. With increasing pressure, the is strongly enhanced, and a broad shoulder-like anomaly in the (T) curve appears and becomes distinct, which is reminiscent of the valence fluctuating systems. The effective mass, which is deduced from the A value of the Fermi liquid relation (T) = 0 +AT 2, is strongly enhanced, indicating that YbCu2Ge2 changes to the heavy fermion system, i.e. the effective mass at 24 GPa roughly 40 times larger than that at 0.6 GPa. In addition, the strong enhancement of the residual resistivity is observed above 10 GPa, and correspondingly the mass also starts to increase drastically. With increasing pressure, the Yb-valence determined by the XANES experiments at room temperature increases strongly from ~2.4+ at ambient pressure to ~2.8+ at 10 GPa, and gradually on further pressure. The heavy fermion state is found to be correlated with a valence change. The present experimental results are compared with the results of YbCu2Si2 under pressure. [1] N. D. Dung et al., J. Phys. Soc. Jpn. 78 (2009) 084711. [2] A. Fernandez-Panella et al., Phys. Rev. B 84 (2011) 134416

Poster 03

Tuning the Properties of CeCoIn5 by Doping with Ru

M. N. Ou1, K. Gofryk2, R. E. Baumbach2, E. D. Bauer2, J. D. Thompson2, F. Ronning2, Y. Y. Chen1, J. M. Lawrence2

1 Institute of Physics, Academia Sinica, Taipei, Taiwan

2 Los Alamos National Laboratory

CeCoIn5, which has a superconducting transition temperature of 2.3 K, provides a convenient stage to study the evolution of superconductivity and magnetism with chemical doping, pressure, or magnetic field close to a quantum critical point (QCP). Previous studies have explored the effects of electron doping, magnetic field, and high pressure on this system. To determine the effects of negative pressure and hole-doping (for which evolution into an antiferromagnetic state is anticipated) we have grown single crystals of CeCo1-xRuxIn5 in Indium flux. The crystal structure of these Ru-doped samples was identified by powder XRD as the HoCoGa5-type; the lattice constants are about 0.3% larger than in CeCoIn5. This crystal structure is maintained up to the nominal doping level x=0.5; the samples are two-phase for larger doping. The temperature Tmax of the maximum of the electrical resistivity (which is often identified as the coherence temperature T*) and the superconducting transition emperature TC decrease monotonically with increasing Ru content. Transport and thermodynamic data will be compared and contrasted with results from Rh and Cd doping.

Poster 04

Pressure effect on anisotropic electrical resistivity of Hg-doped heavy-fermion CeRhIn5

S. Seo, E.D. Bauer1, J.D. Thompson1, T. Park.

Department of Physics, Sungkyunkwan University, 440-746, Suwon, South Korea

1Los Alamos National Laboratory, 87545, Los Alamos, USA

The heavy-fermion compound CeRhIn5 is a prototypical antiferromagnet where Ce 4f moments align below 3.8 K. With increasing pressure, the antiferromagnetic ordering of CeRhIn5 disappears and the superconducting state emerges. When doped with Hg, the antiferromagnetic transition TN initially decreases and develops a different magnetic structure with further increasing Hg concentration. In this research, we focused on a 0.45 % Hg-doped CeRhIn5, where TN is suppressed from 3.8 K to 3.4 K and the magnetic structure is same as that of the undoped compound with Q=(1/2, 1/2, 0.298). By applying hydrostatic pressure, we suppressed TN to zero and measured the anisotropic electrical transport measurements for the electrical current applied within and perpendicular to the Ce-In plane. The difference of phase diagram and evolution of the anisotropic transport property across the quantum critical point will be discussed.

Poster

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Poster 06

Temperature dependent Kondo resonance bands in CeCoGe2: DFT+DMFT approach

Hong Chul Choi1, B. I. Min2, K. Haule3, G. Kotliar3, and J. H. Shim1,2

1Department of Chemistry, Pohang University of Science and Technology, Pohang 790-784,

Korea 2Department of Physics, Pohang University of Science and Technology, Pohang 790-784,

Korea 3Department of Physics, Rutgers University, Piscataway, NJ 08854, USA

We have investigated the formation of the Kondo resonance (KR) band in the heavy

fermion CeCoGe2 using the combined approach of the density functional theory (DFT) and the dynamical mean field theory (DMFT). The low temperature (T) spectral function shows the dispersive KR states in momentum space, which is well consistent with the experimental observation. The size of the induced hybridization gap is rather insensitive to T. During the evolution from the spdbands at highTto the dispersive KR bands at low T, whose topologies are different each other, we have found the existence of kinks in the spectral function near EF. We suggested that the kink can be intrinsically observed in measuring spdconduction bands during the formation of the fully coherent KR band.

Poster 07

Ferromagnetism in the Kondo lattice model

Robert Peters and Norio Kawakami

Department of Physics, Kyoto University, Kyoto, 606-8502, Japan

The Kondo lattice model has been intensively studied for the last thirty years as a fundamental model for heavy fermions, Kondo insulators, and transition metals, e.g. the manganites. Yet, the understanding is far from complete. Recently (Phys. Rev. Lett. 108, 086402 (2012)), we revealed the intriguing properties of

the ferromagnetic state formed in the Kondo lattice model (antiferromagnetic coupling): while the majority-spin electrons are metallic, the minority-spin electrons form an insulating state. Thus when entering the ferromagnetic state and further lowering the temperature, one spin

channel is completely screened and does not participate in transport anymore. Therefore, we have called this intriguing state “spin-selective Kondo insulator”. In our recent work we studied this effect in infinite dimensions using dynamical mean field theory. This time we want to focus on the ferromagnetic state in the one dimensional Kondo lattice model. In one dimension, the density matrix renormalization group gives us the opportunity to precisely calculate ground state properties also including non-local correlations. Thus, using the density matrix renormalization group, we will further study the ferromagnetic state in the Kondo lattice model explaining the underlying physics which lead to this intriguing properties.

Poster 08

High resolution angle-resolved photoemission spectroscopy study on Ba1-xKxFe2As2

Q. Q. Ge, Y. Zhang, M. Xu, and D. L. Feng*

Physics Department, Surface Physics Laboratory (National key laboratory), and Advanced

Materials Laboratory, Fudan University, Shanghai 200433, P. R. China

To have a detailed knowledge of the superconducting gap for each band is essential for understanding the electron pairing mechanism in iron-based superconductors. We here study the doping evolution and the photon-energy dependence of the superconducting gap on Ba1-

xKxFe2As2for the bands near zone center on a wide doping range with high resolution angle-resolved photoemission spectroscopy. Our analysis indicatesthat the kz anisotropy evolution of the superconducting gaps getting remarkable since optimal doped to overdoped regime, while these gaps shows little kz dependence in underdoped samples. Furthermore, we revealed that the doping evolution of three-dimensional gap structure is in company with the band structure evolution, whichwould giveconstraints on the available theories on iron-based superconductors.

Poster 09

Angle-resolved Photoemission Study of SrFe2(As0.65P0.35)2

H. Suzuki a, T. Yoshida a, L. C. C. Ambolode II a, S. Ideta a, A. Fujimori a,d, H. Kumigashira b, K. Ono b, T. Kobayashi c, S. Miyasaka c,d, S. Tajima c,d

a University of Tokyo, Tokyo, Japan

b KEK, Photon Factory, Ibaraki, Japan c Osaka University, Osaka, Japan

d JST-TRIP, Tokyo, Japan

Since the discovery of superconductivity in iron-pnictide materials, the symmetry of the superconducting order parameter has been under intense debate. Isovalent-substitution to the parent compound BaFe2As2 brings about chemical pressure and suppresses antiferromagnetic order, which induces superconductivity with Tc up to 30K in BaFe2(As1-xPx)2 (Ba122P) [1]. The most striking feature is unconventional nodal structure as seen in NMR [2], penetration depth, and thermal conductivity measurements [3]. Several theoretical explanations have been proposed afterwards in order to explain the origin of the nodes in the framework of spin-fluctuation- or orbital-fluctuation-mediated mechanisms. SrFe2(As1-xPx)2 (Sr122P) has a similar phase diagram to Ba122P with the highest Tc~26K.

The contrasting feature between Sr122P and Ba122P is the residual density of states (Nres) at the Fermi level in the superconducting phase. The ratio of Nres to the density of states in the normal state N0 of Sr122P is shown to be three times larger than that of Ba122P by 31P-NMR measurement [4]. This result indicates that the nodal structure could be more prominent in Sr122P and/or multiband nature plays an important role in the low-energy excitations, making this system a good candidate for the study of the pairing symmetry. In order to clarify its electronic structure, we have performed high-resolution angle-resolved photoemission study of Sr122P (x=0.35). Measurements with hv=30-86eV have revealed strongly three-dimensional three hole Fermi surfaces at the center and almost two-dimensional electron Fermi surfaces at the corner of the Brillouin zone. We have also found that the superconducting gap size is strongly band dependent, which may explain the NMR results at low temperatures. keywords : Iron-pnictides, order parameter, nodes

[1] S. Kasahara et al., Phys. Rev. B 81, 184519 (2010). [2] Y. Nakai et al. Phys. Rev. B 81, 020503(R) (2010). [3] K. Hashimoto et al., Phys. Rev. B 81, 220501(R) (2010). [4] T. Dulguun et al., arXiv:1108.4480

Poster 10

Photoemission study of iron based superconductor Eu(Fe1-xRux)2As2

M. Xia1, Z. R. Ye1, M. Xu1, Q. Q. Ge1, R. Peng1, W. H. Jiao2, G. H. Cao2, D. W. Shen3, D. L.

Feng1

1 State Key Laboratory of Surface Physics and Department of Physics, Fudan University, 220

Handan Rd, Shanghai 200433, China 2 Department of Physics, Zhejiang University, Hangzhou, 310027, People’s Republic of

China 3 State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of

Microsystem and Information Technology , Chinese Academy of Sciences, Shanghai 200050, China

Eu(Fe1-x Rux)2As2 is an iron-based superconductor with special properties. Although Ru

substitution of Fe is iso-valent, it can induce superconductivity just as carrier doping. With our ARPES measurements performed at different systems on a variety of samples, we do find that there are many unusual electronic bands compared with other 122 series iron-based superconductor, even with other iso-valent substituted materials, such as BaFe2(As1-x Px)2 and Ba(Fe1-x Rux)2As2, suggesting the complexity of these systems. Recent ARPES measurements on over-doped samples suggest the developments of bands with photon energy are different with those of optimally doped sample, which makes this project more complicated.

Poster 11

Electronic structure of heavily hole-doped KFe2As2 revealed by angle-resolved photoemission spectroscopy

J. Jiang, Y. Zhang, Z. R. Ye, M. Xu, F. Chen, X. P. Shen, B. P. Xie, and D. L. Feng*

Department of Physics, Applied Surface Physics State Key Laboratory, Fudan University,

Shanghai 200433, P. R. China As the extremely hole-doped iron-arsenide Ba1-xKxFe2As2, KFe2As2 arouses much attention

for its unique properties. The electron Fermi surface, which is responsible for the Fermi surface nesting in other iron pnictides [1,2], is absent in KFe2As2. Meanwhile, a possible nodal gap has been discovered by its penetration depth and thermal conductivity measurements, and thus a d-wave like symmetry is proposed [3,4], indicating a pairing symmetry transition from s-wave to d-wave induced by the K-doping. However, a recent theory, which proposed a nodal s-wave superconductivity induced by a non-magnetic intra-band and inter-band interactions between fermions near hole pockets, unifies the paring symmetry between KFe2As2 and Ba1-xKxFe2As2 [5], making this system more complicated. Therefore, it is significant to understand the electronic structure of the heavily hole-doped KFe2As2.

However, so far, no detailed orbital characters has ever been reported, while the orbital characters are proposed to be important for the superconductivity in the iron pnictides. Thus, here we present detailed low-lying band structure measurements of KFe2As2 with polarization-dependent angle-resolved photoemission spectroscopy. Three hole pockets around the Γ/Z point and four small hole pockets around the M/A point have been detected near the Fermi energy. Meanwhile, we could observe strong kz dependence of certain band with the dz

2 orbital below Fermi energy, which is consistent with the result reported elsewhere [1,2]. Around the Z point, the orbital characters of these three bands become more complicated due to the mixing of dz

2, and the dz2 orbital is even strongly mixed into the

middle hole-like band, which might be responsible for the nodal gap behavior observed in this material according to the assumption proposed in BaFe2 (As1-xPx)2 [6]. Our results would help further decide the pairing symmetry in KFe2As2. [1] T. Sato, et al, PRL 103, 047002 (2009). [2] T. Yoshida, et al, Journal of Physics and Chemistry of Solids 72(2011) 465-468. [3] K. Hashimoto, et al, Phy. Rev. B 82, 014526(2010). [4] J. K. Dong, et al, Phy. Rev. Lett 104, 087005(2010). [5] S. Maiti, M.M. Korshunov, and A.V. Chubukov, arXiv:1111.0306v1. [6] Y. Zhang, et al, Nature Physics 8(5), 371(2012).

Poster 12

Angle-resolved and resonance photoemission study of FeTe

L. C. C. Ambolode II1, M. Horio1, H. Suzuki1, S. Ideta1, T. Yoshida1,3, A. Fujimori1,3,

K. Ono2, H. Kumigashira2, L. Liu1, M. Takahashi1, T. Kakeshita1,3, S. Uchida1,3

1Department of Physics, University of Tokyo, Tokyo 113-0033 , Japan 2Photon Factory, IMSS, KEK, Ibaraki 305-0801, Japan

3JST, TRIP, Tokyo 102-0075, Japan

Electron correlation effects in iron-based superconductors (FeSCs) have been investigated

extensively in a number of theoretical and experimental studies [1-2]. Among the FeSCs, FeTe compound was found to have a relatively high electron correlation. In this study, we have performed angle-resolved and resonance photoemission spectroscopy on FeTe compound to examine the electron correlation effects on its electronic structure.

From resonance photoemission, valence-band spectra of FeTe were taken at various photon energies. It was observed that Fe 3p→3d resonance occurs around hv ~ 55 eV. FeTe partial density of states was deduced from the difference of the on-resonance and off-resonance spectra. Employing self-energy analysis, we were able to calculate the mass renormalization of FeTe which is about 1.4. This value is small compared to the previous FeTe0.42Se0.58 ARPES [1] result, but nearly same as FeSe [3] and 1111 AIPES [4] results. The smaller mass renormalization in FeTe resonance photoemission suggests that deep bands are weakly correlated compared with bands crossing the Fermi level.

In order to examine thoroughly the electronic structure of FeTe, angle-resolved photoemission was performed on the same FeTe compound. The valance-band spectra were then compared with the resonance photoemission spectra and band calculations in order to determine the orbital characters. The band structure qualitatively agrees with the resonance photoemission spectra and the band calculations. [1] A. Tamai, et al., Phys. Rev. Lett. 104, 097002 (2010). [2] Z. P. Yin et al., Nature Materials 10, 932 (2011). [3] T. Miyake et al, J. Phys. Soc. Jpn. 79, 044705 (2010). [4] W. Malaeb et al., J. Phys. Soc. Jpn. 77, 093714 (2008).

Poster 13

Evolution of the charge dynamics with P substitution in BaFe2(As1-xPx)2 investigated by optical spectr

oscopy

M. Nakajima a,b,c, T. Tanaka b,c, K. Kihou a,c, C. H. Lee a,c, A. Iyo a,c, T. Kakeshita b,c, H. Eisaki a,c, and S. Uchida b,c

a National Institute of Advanced Industrial Science and Technology, Tsukuba, Japan b Department of Physics, University of Tokyo, Tokyo, Japan

c JST, Transformative Research-Project on Iron-Pnictides, Tokyo, Japan BaFe2As2 is one of the representative parent compounds of iron-arsenide superconduc

tors. It exhibits a structural and magnetic phase transition from paramagnetic-tetragonal to antiferromagnetic-orthorhombic phase at ~ 140 K [1,2]. This magnetostructural ordered phase is suppressed by various doping processes, chemical substitution at various lattice sites, giving way to superconductivity. Frequently studied chemical substitutions of Co for Fe and K for Ba correspond to electron doping and hole doping, respectively [3,4]. So far, the Co-doped system has been mainly studied because of the ease of the single-crystal growth, but to deeply understand the physics in the doped iron arsenides, it is indispensable to investigate another system. Substitution of P for As also induces superconductivity [5]. P-substituted BaFe2(As1−x

Px)2 is a distinguishing system in that the replacement of As for isovalent P supplies neither electrons nor holes, and therefore, does not break the balance between the electron and hole numbers in undoped BaFe2As2. We have succeeded in synthesizing sizable single crystals of BaFe2(As1−xPx)2 over the entire range of the P content x and performed the systematic study of the in-plane optical spectra. It turns out that the P substitution increases weight of a Drude component corresponding to coherent carrier motion without changing the total low-energy spectral weight. The result well explains the decrease in the resistivity with increasing x. From the analysis of temperature dependence of the in-plane resistivity which is predominantly determined by the coherent Drude term, the coefficient of the T-linear term correlates with the superconducting Tc, suggesting that relevant electron-boson interaction giving rise to the T-linear scattering has an intimate relation with superconductivity in the iron arsenides. keywords : optical spectroscopy, isovalent substitution, iron-pnictide superconductor [1] M. Rotter et al., Phys. Rev. B 78, 020503(R) (2008). [2] Q. Huang et al., Phys. Rev. Lett. 101, 257003 (2008). [3] M. Rotter, M. Pangerl, M. Tegel, and D. Johrendt, Angew. Chem. Int. Ed. 47,

7949 (2008). [4] F. Rullier-Albenque, D. Colson, A. Forget, and H. Alloul, Phys. Rev. Lett. 103,

057001 (2009). [5] S. Jiang et al., J. Phys.: Condens. Matter 21, 382203 (2009).

Poster 14

Superconductivity and Magnetic Ordering of EuFe2(As0.7P0.3)2 under High Pressure

Shigeki Tanaka1, Atsushi Miyake1, Tomoko Kagayama1, Katsuya Shimizu1,

Jing Guo2, Genfu Chen3, Liling Sun2

1 KYOKUGEN, Osaka University, Toyonaka Osaka 560-8531, Japan 2 Institute of Physics and Beijing National Laboratory for Condensed Matter Physics,

Chinese Academy of Sciences, Beijing 100190, China 3 Department of Physics, Renmen University of China, Beijing 100872, China

A pressure induced superconductor EuFe2As2 has two magnetic orderings derived from Fe2+

and Eu2+ at ambient pressure. When the SDW transition (Fe2+) is suppressed by increasing pressure or doping isovalent P to the As site (EuFe2(As1-xPx)2), the superconductivity appears at around 2.5 GPa or the P-content of 0.2 ≤ x ≤ 0.4[1,2]. The superconductivity coexists with the magnetic ordering (Eu2+). Although the pressure dependence of the superconducting transition temperature (Tc) and the magnetic ordering temperature (Tm) for EuFe2As2 have been determined strictly, those for EuFe2(As1-xPx)2 have been determined only up to 0.8 GPa[1,3,4]. We focused on the interplay between the superconductivity and the magnetic ordering (Eu2+)

of EuFe2(As0.7P0.3)2 (x = 0.3) under high pressure, and carried out the electrical resistance and the specific heat measurements on singlecrystalline EuFe2(As0.7P0.3)2 under high pressure and determined the pressure dependence of Tc and Tm up to 2.2 GPa. Tc and Tm are ~23 K and ~19 K at ambient pressure, respectively, and Tc decreases and Tm increases with increasing pressure. Our results are corresponding to the temperature-pressure phase diagram of EuFe2As2 above 2.5 GPa. [1] N. Kurita et al., Phys. Rev. B 83, (2011) 214513. [2] G. Cao et al., J. Phys.: Condens. Matter 23, (2011) 464204. [3] K. Matsubayashi et al., Phys. Rev. B 84, (2011) 024502. [4] H. B. Banks et al., Physica C 471, (2011) 476.

Poster 15

Electronic structure and anisotropy of Sr2VO3FeAs superconductor.

Hyo Seok Ji and Ji Hoon Shim

Department of Chemistry, Pohang University of Science and Technology (POSTECH)

Electron correlation effect on Fe 3d orbital has very important role in describing electronic

structure and anisotropy of iron-based superconductors.[1] By using combination of the density functional theory (DFT) and dynamical mean field theory (DMFT), the electron correlation effect can be described well. In this study, we have investigated the electronic structure and anisotropy of Sr2VO3FeAs superconductor. Simple DFT result shows mixed band structures of Fe 3d and V 3d orbital, but the experimental result shows only Fe 3d band near the Fermi level.[2] The DFT+U method explains insulating V layer structure correctly[2, 3] but it cannot describe whole electronic structure such as renormalized Fe 3d bands. So we apply the electron correlation effect on the V 3d orbital as well as the Fe 3d orbital using DFT+DMFT. With antiferromagnetic(AFM) ordering, V 3d bands split into -1 eV and 1 eV region, which is consistent with experimental ARPES result.[2] Also we calculate electrical anisotropy = xx/zz which is important for determining dimensionality effect in iron-based superconductors. Calculated anisotropy value is much smaller than simple DFT result and the result is well consistent with recent experimental result. This trend is also consistent with the trend of previous work[1]. References [1] H. S. Ji, G. Lee, and J. H. Shim, Phys. Rev. B 84, 054542 (2011). [2] T. Qian et al., Phys. Rev. B 83, 140513(R) (2011). [3] H. Nakamura and M. Machida, Phys. Rev. B 82, 094503 (2010).

Poster 16

Phase diagram and calorimetric properties of NaFe1−xCoxAs

A. F. Wang, X. G. Luo, Y. J. Yan, J. J. Ying, Z. J. Xiang, G. J. Ye, P. Cheng, Z. Y. Li, W.

J. Hu, and X. H. Chen*

Hefei National Laboratory for Physical Science at Microscale and Department of Physics, University of Science and Technology of China

Hefei, Anhui 230026, People’s Republic of China

We measured the resistivity and magnetic susceptibility to map out the phase diagram of single crystalline NaFe1−xCoxAs. Replacement of Fe by Co suppresses both the structural and magnetic transitions; however, it also enhances the superconducting transition temperature (Tc) and superconducting component fraction. Magnetic susceptibility exhibits temperature-linear dependence in high temperatures up to 500 K for all the superconducting samples, but such behavior suddenly breaks down for the nonsuperconducting overdoped crystal, suggesting that the superconductivity is closely related to the T-linear dependence of susceptibility. Analysis on the superconducting state specific heat of the optimally doped crystal provides strong evidence for a two-band s-wave order parameter with gap amplitudes of 78.1/)0(1 cBTk and 11.3/)0(2 cBTk , being consistent with the nodeless gap

symmetry revealed by angle-resolved photoemission spectroscopy experiment.

Poster 17

Evidence for nodeless superconducting gap in NaFe1-

xCoxAs from low-temperaturethermal conductivity measurements

S. Y. Zhou1, X. C. Hong1, X. Qiu1, B. Y. Pan1, Z. Zhang1, X. L. Li1, W. N. Dong1,

A. F. Wang2, X. G. Luo2, X. H. Chen2, and S. Y. Li1*

1 State Key Laboratory of Surface Physics, Department of Physics, and Laboratory of Advanced Materials, Fudan University, Shanghai 200433, P. R. China

2 Hefei National Laboratory for Physical Science at Microscale and Department of Physics, University of Science and Technology of China, Hefei, Anhui 230026, China

The thermal conductivity of optimally doped NaFe0.972Co0.028As (Tc~20 K) and

overdopedNaFe0.925Co0.075As (Tc~11 K) single crystals were measured down to 50 mK. No residual linearterm κ0/T is found in zero magnetic fields for both compounds, which is an evidence for nodelesssuperconducting gap. Applying field up to H = 9 T (~ ¼Hc2) does not noticeably increaseκ0/T in NaFe1.972Co0.028As, which is consistent with multiple isotropic gaps with similar magnitudes.Theκ0/Tof overdoped NaFe1.925Co0.075As shows relatively faster field dependence, indicatingthe increase of the ratio between the magnitudes of different gaps, or the enhancement of gapanisotropy upon increasing doping.

Poster 18

Fabrication of Potassium doped Iron-based superconducting thin films

by pulsed laser deposition system.

Nam Hoon Leea, Young Hoon Oha, W. N. Kanga,*

BK21 Physics Division and Department of Physics, Sungkyunkwan University, Suwon 440-746, Korea

Among the various Fe-based superconductors, potassium doped BaFe2As2 is favorable for

application because of its higher transition temperature and a low anisotropy compared to other iron based superconductors. To study the superconductivity and applicable aspects, high quality thin films should be fabricated. However, it is difficult to fabricate thin films because of the high volatility of potassium. In this paper, we show the details of fabricating technique of Ba1-xKxFe2As2 films by ex-situ PLD method in various conditions and physical properties of these films. Barium ratio in target is controlled to make films with various potassium doping rate. An annealing temperature and amount of potassium are also controlled to find out optimal condition of fabricating films. Keywords : iron-based, films, PLD

Poster 19

Temperature and doping dependent cross-sectional analysis of Fourier-transform scanning tunneling

spectroscopy of cuprate superconductor

Jhinhwan Lee, Shyam Mohan*, Jimin Kim*, Seokhwan Choi and Chanhee Kim

KAIST, Department of Physics, Daejeon, Korea

With the real-space Green’s function-based Bogoliubov quasiparticle interference analysis technique originally suggested in [1], the correlation between the experimental data and the simulation is significantly enhanced. We applied this technique to simulate the temperature and doping dependent evolution of QPI signals in high symmetric axes and compared them with the experimental data published [2,3]. We have used the gap function of the form

sgn cos2 |cos2 | fitted to the gap function data in the same literature. We have included the scattering rate of the quasiparticle proportional to |E| with the proportionality constant dependent on doping and the thermal broadening of the tunneling spectra in the imaginary part of the self energy. Even with this simple theoretical model, we could reproduce lots of unusual non-octet features in the CS-FTSTS line cuts. For example, the increased asymmetry of the q1 signal at pseudogap temperature is reproduced very precisely. The residual discrepancy will need a more elaborate theoretical models. The details of our simulation methods and results will be discussed.

[1] T.S. Nunner, et. al., Phys. Rev. B 73, 104511 (2006). [2] Y. Kohsaka, et al., Nature 454, 1072-1078 (2008) [3] J. Lee, et al., Science 325, 1099 (2009) *These researchers contributed equally to this work. †The experimental data are kindly supported by J.C.Davis group in Cornell University and Brookhaven National Laboratory. Doping-dependent data and temperature-dependent data are from ref [2] and [3] respectively.

Poster 20

Evidence for a pseudogap in ab-plane optical conductivity measurements and its applications

Il Ho Jung and Jungseek Hwang

Department of Physics, Sungkyunkwan University, Suwon, Gyeonggi-do 440-746, Korea

The pseudogap is more difficult to identify in the ab-plane transport. While it was clear

early on that the ab-plane absorption showed an unmistakable decrease at energies below pg, a clear interpretation in terms of a pseudogap was problematic since it is difficult to separate the effects of a pseudogap (a partial gap in the density of states) and a sharp peak in the spectrum of inelastic excitations (a magnetic resonance mode) since both give a similar feature near pseudogap energy scale. Further, studies of the real part of the conductivity did not show the expected reduction in optical spectral weight below the pseudogap energy. This remains unexplained. The real part of the in-plane optical self-energy spectra in underdoped Bi2Sr2CaCu2O8+ (Bi-2212) and ortho II YBa2Cu3O6.50 contain new and important information on the pseudogap. Using a theoretical model approach, a major new finding is that states lost below the pseudogap pg are accompanied by a pileup of states just above this energy. The pileup along with a sharp mode in the bosonic spectral function leads to an unusually rapid increase in the optical scattering rate as a function of frequency and a characteristically sloped peak in the real part of the optical self-energy. These features are not found in optimally doped and overdoped samples and represent the clearest signature so far in the in-plane optical conductivity of the opening of a pseudogap. We introduce the new pseudopgap model and apply it to some undedoped cuprate systems.

Poster 21

Absence of pseudogap in electron-doped T'-Pr1.2La0.7Ce0.1CuO4

revealed by angle-resolved photoemission spectroscopy

M. Horio1, T. Yoshida1, H. Suzuki1, L. C. Ambolode1, A. Fujimori1, T. Mizokawa2, K. Ono3, H. Kumigashira3, Y. Mori4, T. Adachi4, Y. Koike4

1Department of Physics, University of Tokyo, Japan, 2Graduate School of Frontier Sciences, University of Tokyo, Japan, 3Photon Factory, Institute of Materials Structure Science, KEK,

Japan, 4Department of Applied Physics, University of Tohoku, Japan, E-mail address: [email protected]

In the electron-doped high temperature cuprate superconductor (e-HTSC) Pr1-xLaCexCuO4,

the antiferromagnetic (AFM) ordering is rapidly suppressed with increasing doping level [1] compared to other e-HTSCs, reflecting the smaller charge-transfer gap of the parent insulator [2]. Annealing effect on the electronic structure of the same system has been studied by Richard et al. [3]. In this study, we have performed an ARPES measurement on an annealed Pr1.3-xLa0.7CexCuO4 (x=0.10) sample which has a transition temperature Tc of 27K. Although most of the e-HTSCs show pseudogaps from the optimally doped (x~0.15) to the underdoped region [4], the present ARPES spectra with x=0.10 show clear peaks on the entire Fermi surface and do not show signatures of the pseudogap (Fig. 1). The absence of the pseudogap in spite of the low doping level can be attributed to the suppression of AFM spin fluctuations due to the small charge-transfer gap of the parent insulator. [1] M. Fujita et al., Phys. Rev. B 67, 014514 (2003). [2] Y. Ohta et al., Phys. Rev. Lett. 66, 1228 (1991). [3] P. Richard et al., Phys. Rev. Lett. 99, 157002 (2007). [4] M. Ikeda et al., Phys. Rev. B 80, 014510 (2009).

Fig. 1. (a) Fermi surface mapping taken at h =55eV. (b)　 EDCs at kF in each cut indicated in panel (a).

Poster 22

The angle and frequency dependences of the self-energy induced by the spin fluctuations for the cuprate

superconductors

Seung Hwan Hong, Han-Yong Choi

Department of Physics, SungKyunKwan University,Suwon, Korea

We solve the momentum resolved d-wave Eliashberg equation to investigate the consistency of the spin fluctuation induced superconductivity theory for the cuprates. The effective interaction between electrons (Eliashberg function) is modeled in terms of the magnetic excitation spectrum measured by the inelastic neutron scattering on the optimally doped LSCO superconductors reported by Vignolle et al [1]. The magnetic excitation spectrum have two energy scales: the resonance mode near 40 – 70 meV and the incommensurate peak around 18 meV. The resonance mode has a peak at (π,π). The low energy incommensurate part makes a nonmonotonic momentum dependence of the diagonal and off-diagonal self-energies. On the other hand, the resonance mode makes a monotonic momentum dependence of the self-energy. The angle dependence of the superconducting gap is influenced by the effects of these two energy scales. These results are compared with the gap from the ARPES experiments [2]. [1] B. Vignolle et al., "Two energy scales in the spin excitations of the high-temperature

superconductor La2−xSrxCuO4", Nature Physics 3, 163 (2007). [2] K. Terashima et al., "Anomalous Momentum Dependence of the Superconducting

Coherence Peak and Its Relation to the Pseudogap of La1.85Sr0.15CuO4", Phys. Rev. Lett., 99, 017003 (2007).

* This work was supported by National Research Foundation (NRF) of Korea through Grant No. NRF 2011-0005035.

Poster 23

Eliashberg function of the underdoped and overdoped Bi2212 superconductors deduced from the high resolution

laser ARPES intensity

Jin Mo Boka, Han-Yong Choia, Junfeng Heb, X.J. Zhoub , C.M. Varmac

a Department of Physics, SungKyunKwan University, Suwon 440-746, Korea b Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China.

c Department of Physics and Astronomy, University of California, Riverside, CA 92521, USA.

The analysis of the spectra in the superconducting state, using the Eliashberg formalism, provides the fluctuation spectrum responsible for pairing. To investigate the mechanism of the high Tc superconductors, we extract the diagonal and off-diagonal Eliashberg functions, α2F(+) and α2F(-), of underdoped and overdoped Bi2212 superconductors deduced from the laser ARPES intensity. By performing the MDC (momentum distribution curves) fitting of the ARPES intensity employing the superconducting Green's function, the diagonal and off-diagonal self-energies, Σ and , along several cuts in the Brillouin zone are extracted. Then, the diagonal and off-diagonal Eliashberg functions are deduced by inverting the d-wave Eliashberg equation using the corresponding self-energies. We will report the momentum and frequency dependence of the self-energies and Eliashberg functions. We then compare these results with other experiment and model calculation results. * This work was supported by National Research Foundation (NRF) of Korea through Grant No. NRF 2011-0005035.

Poster 24

Low-energy spin excitation in coexistent phase of antiferromagnetism and d-wave superconductivity

*Hyun-Jung Lee and **Tetsuya Takimoto

*Korea Institute for Advanced Study, Seoul 130-722, South Korea

**Asia Pacific Center for Theoretical Physics, Pohang 790-784, South Korea

Nuclear quadrupole resonance measurements have shown evidences that the heavy fermion compound CeRhIn5 exhibits a coexistent phase with commensurate antiferromagnetism and d-wave superconductivity. In order to clarify the nature of the spin-excitations in the coex-istent phase, we have applied the RPA method to an itinerant model, where the effective interaction is given by two mean-field terms of commensurate antiferromagnetism and d-wave superconductivity[1]. It is shown that, around the transition line between the antiferromagnetic and the coexistent states, a low-energy incommensurate spin-excitation is found to develop due to Fermi surface nesting. This feature reminds of the switching of magnetic ordering wave vector observed in the neutron diffraction. Further, we also calculate spin relaxation rate, which gives a reasonable explanation of the temperature dependence of NQR relaxation rate in the system with the coexistent ground state. [1] arXiv:1204.5032

Poster 25

Interplay between superconductivity and nematic order

Eun-Gook Moon

University of California, Santa Barbara We study the interplay between nematic order and superconductivity, motivated by a recent

experiment on FeSe observing strongly distorted vortex shapes and suppression of superconductivity at twin boundaries. We show that the nematic order strongly enhances the anisotropy in the superconducting

coherence length, beyond that expected from considerations of the Ginzburg-Landau theory. We obtain universal functions describing the coupling between the nematic order and

superconductivity, and discuss connections of our results to the experiments. We also consider mechanism of suppression at twin boundaries and nematic order parameter

and superconductivity shows non-trivial interplay behaviors.

Poster 26

Effects of spin fluctuations on critical behaviors of itinerant weak antiferromagnets

Rikio Konno1, Nobukuni Hatayama1, Yoshinori Takahashi2

1 Kinki University Technical College,

2 Graduate School of Material Sciences, University of Hyogo

Magnetic and thermal critical behaviors of itinerant electron magnets have been intensively studied around the quantum critical point. On the other hand, so much interest has not been paid on crossover phenomena between classical and quantum critical behaviors. This study therefore clarifies how the predominance of thermal and quantum spin fluctuations of itinerant weak antiferromagnets will change as systems approach the quantum critical point based on the spin fluctuation theory [1]. Above the Neel temperature TN we found that the temperature dependence of the inverse of staggered magnetic susceptibility of itinerant weak antiferromagnets changes from the classical (T-TN)2 –linear behavior to the quantum (T-TN)3/2 –linear one around the characteristic temperature T* with increasing temperature, where T is absolute temperature. In the vanishing limit of TN, the classical critical region disappears. The results show close similarity with those of the itinerant weak ferromagnets [2]. References [1]. Yoshinori Takahashi, J. Phys.: Condens. Matter 13 (2001) 6323. [2]. Yoshinori Takahashi, Meeting Abstracts of the Physical Society of Japan, Vol.67, Issue 1, Part 3, page 524 in Japanese.

Poster 27

Effects of substrate temperature on microstructure and superconducting properties of MgB2 coated Hastelloy

tapes

O.Y. Lee a, Mahipal Ranot a, K. H. Cho a, W. N. Kang a,*, S. Oh b, K. C. Chung c

a Sungkyunkwan University, Suwon, Korea

b National Fusion Research Institute, Daejeon, Korea c Korea Institute of Machinery and Materials, Daejeon, Korea

We have investigated the effects of substrate or growth temperature on microstructure and

superconducting properties of MgB2 coated Hastelloy tapes. The coating of MgB2 on Hastelloy tapes was performed by depositing MgB2 films directly on the flexible metallic Hastelloy tapes at various temperatures of 520–600 °C using hybrid physical-chemical vapor deposition (HPCVD) technique. The MgB2 coated conductors exhibited the critical temperatures ranging between 37.5 and 38.5 K with sharp superconducting transition width. X-ray diffraction analysis revealed that the MgB2/Hastelloy coated conductors are polycrystalline in nature. The surface morphologies were examined by scanning electron microscopy. It was found that the MgB2 coated conductor grown at a low temperature of 520 °C has dense microstructure with good grains connectivity, whereas deterioration of the grains connectivity and void formations were observed upon increasing the growth temperature from 520 to 600 °C. The critical current density (Jc) of the order of 105 A/cm2 under 3 T was obtained for the MgB2 coated conductor grown at 520 °C. The critical current density of MgB2 coated conductor is enhanced with decreasing growth temperature. These results suggest that the fabrication of MgB2 coated conductors at low temperature could be useful for large scale applications.

Poster 28

Vortices perpendicular to an inplane magnetic field in noncentrosymmetric interface superconductors

Kazushi Aoyamaa,b,c and Manfred Sigristb

a Young Researcher Development Center, Kyoto University, Japan

b Institute for Theoretical Physics, ETH Zurich, Switzerland c Department of Physics, Kyoto University, Japan

The discovery of bulk superconductivity in the heavy-fermion material without inversion

symmetry, CePt3Si, triggered extensive studies of non-centrosymmetric superconductivity, and a large variety of physical properties have been discussed in this class of superconductivity [1].

The interface between the band insulators LaAlO3 and SrTiO3 is a non-centrosymmetric 2D electron system with a Rashba spin-orbit coupling effect originating from the lack of inversion symmetry with respect to the interface [2]. It has been known that the interface exhibits superconductivity [3], and real space imaging experiments have detected local magnetic patterns which might be interpreted as ferromagnetic patches coexistent with the superconducting (SC) phase [4]. Motivated by these experiments, we theoretically investigate magnetic properties of a 2D non-centrosymmetric superconductor in an inhomogeneous environment with an in-plane magnetic field or magnetization.

In this presentation, we will show that in the case with inhomogeneity in the Rashba spin-orbit coupling, vortices perpendicular to the interface appear at the inhomogeneity as a result of an inhomogeneous field-induced helical SC state.

Reference [1] V.P. Mineev and M. Sigrist, Non-Centrosymmetric Superconductors: Introduction and

Overview (Lecture Notes in Physics), edited by E. Bauer and M. Sigrist, Springer 2011, Chapter 4.

[2] S. Thiel et al., Science 313, 1942 (2006). [3] N. Reyren et al., Science 317, 1196 (2007). [4] J. A. Bert, et al., Nature physics 7, 767 (2011).

Poster 29

Emergence of Chiral Orbital Angular Momentum and Circular Dichroism ARPES

Jin-Hong Park1, Choong H. Kim2, Jun-Won Rhim3, and Jung Hoon Han1,4

1 Department of Physics and BK21 Physics Research

Division, Sungkyunkwan University, Suwon 440-746, Korea 2 Department of Physics and Astronomy, Seoul National University, Seoul 151-742, Korea

3 School of Physics, Korea Institute for Advanced Study, Seoul 130-722, Korea 4 Asia Pacific Center for Theoretical Physics, POSTECH, Pohang, Gyeongbuk 790-784,

Korea We show that the chiral orbital angular momentum (OAM) can emerge at the metal surfaces

by using the tight-binding method and first-principle calculation. Inversion symmetry breaking at the surface is responsible for the formation of chiral OAM and spin-orbit interaction is not necessary for the chiral OAM. The circular dichroism (CD) angle-resolved photoemission (ARPES) is an efficient method to detect chiral OAM, and we derive explicit formulas relating the CD-ARPES signal to the existence of nonzero chiral OAM in the band structure. Explicit formulas for the p- and d-orbital show that the CD-ARPES signal is proportional to the OAM in the momentum space.

Poster 30

Electronic State of 1D Iron-Selenide BaFe2Se3

T.Kakeshita a, R.Suzukia, M.Takahashia, L.Liua, S.Uchidaa, K.Kihoub, A.Iyob, H.Eisakib

a Department of Physics, University of Tokyo

b National Institute of Advanced Industrial Science and Technology (AIST) In spite of an identical structure to AFe2As2 (122, A=Ba, Sr, Ca), the iron-selenide

superconductor A1-xFe2-ySe2 (A= alkaline metal) demonstrates quite different physical properties from iron-based superconductors such as ReFeAsO (1111, Re = rare earth metal) and 122 system. The parent compound K0.8Fe1.6Se2(245) demonstrates ordering of iron deficiency with a different type of magnetic order from iron-basedsuperconductors and also show an insulating behavior below the temperature, contrary to the metallic behavior of iron-pnictide superconductors[1,2]. The typical Fermi surface for iron-pnictide superconductors have three hole pockets around point and two electron pockets around M poin, whereas the superconducting composition of 245 system have only electron pockets around M point[3]. Since the superconductivity for 245 system is in proximity to the antiferromagnetic insulating state, it is debated whether the electronic state of the parent compound of 245 iron-selenide is a band insulator or a Mott insulator at present. We have investigated the electronic state of 1D iron-chalcogenide BaFe2Se3 by resistivity

and optical spectra with the single crystal. Since the iron atom of the iron-selenide is divalent, BaFe2Se3 is analogue to theparent compound for 245 system. Our results show that BaFe2Se3 is a strong insulating behaviour and imply that aMott gap is preferable to a band gap for the origin of insulating BaFe2Se3. keywords : Iron-selenide, Mott insulator, Band insulator, strongly-correlated system [1] M.-H.Fang et al., "Fe-based superconductivity with 31K bordering anantiferromag

netic insulator in (Tl,K)FexSe2", EuroPhys. Lett. 94, 27009 (2011). [2] F.Ye et al., "Common Crystalline and Magnetic Structure of Superconducting A2F

e4Se5 (A=K,Rb,Cs,Tl) Single Crystals Measured Using Neutron Diffraction", Phys. Rev. Lett. 107, 137003 (2011).

[3] T.Qian et al., "Absence of a Holelike Fermi Surface for the Iron-Based K0.8Fe1.7Se2 Superconductor Revealed by Angle-Resolved Photoemission Spectroscopy", Phys. Rev. Lett. 106, 187001 (2011).

Poster 31

A Softening of Singlet Bound States in the Spin-Ladder like Compound BiCu2PO6

K.Y. Choi1, J. W. Hwang1, P. Lemmens2, D. Wulferding2, H. Nojiri3, G.-J. Shu4,

and F. C. Chou4

1 Department of Physics, Chung-Ang University, Seoul 156-756, Republic of Korea 2 ICMP, TU Braunschweig, D-38106 Braunschweig, Germany

3 IMR, Tohoku University, Sendai 980-8577, Japan 4 CCMS, National Taiwan University, Taipei, Taiwan

Low-energy magnetic excitations are investigated to elucidate the novel magnetic

behaviours of the spin-ladder like compound BiCu2PO6 with a spin gap of 32 K using a Raman spectroscopy and high-frequency Electron Spin Resonance (ESR) . We observe strong ESR signals above a critical field of Hc~22 T when a magnetic field is applied along the a-axis. They are ascribed to antiferromagnetic-like resonances in a field-induced ordered state. The anisotropy of ESR intensity shows the strong mixing between the singlet ground state and the excited states. Magnetic Raman scatterings show pronounced broad two-triplon continuum extending from 28 cm-1 to 1000 cm-1 in (aa), (bb), and (cc) polarizations. This clearly indicates the formation of a spin gap of 14 cm-1= 25 T and is consistent with the ESR results. In addition, we identify three singlet bound states at 24, 64, and 102 cm-1, which are pronounced in (bc) polarization. Remarkably, the singlet bound modes undergo a giant softening and narrowing for temperatures below 50 K, indicative of the instability of a singlet phase. This is discussed as evidence that BiCu2PO6 lies close to a quantum critical point to a magnetic ordered phase due to 3D interladder couplings.

Poster 32

Z2 striped spin liquid in kagome spin ½ Heisenberg antiferromagnets

Michael J. Lawler

Binghamton University, Cornell University

Recent DMRG calculations[1] suggest that the ground state of the spin ½

antiferromagnetic Heisenberg model on the kagome lattice is a gapped spin liquid. In contrast, the gapless U(1) Dirac state was proposed from Gutzwiller projected variational wave function calculations. To resolve these differences, we revisit this problem from a projected BCS wave function perspective with all pairing amplitudes as variational parameters. These time--reversal invariant wave functions span both U(1) and Z2 spin liquids (a proposed instability[2]) and any form of spatial symmetry breaking. By starting from the PSG catalog of Z2 spin liquids[2], we stochastically sample this wave function space and have discovered a lower energy state than the Dirac state with the stripe-like symmetry and some U(1) gauge symmetry breaking. This state is not a dimerization of the lattice. We argue, based on symmetry grounds, that it could arise from the proliferation of monopoles descriped in Ref. [3]. In addition, it likely has a gap suggesting a relationship with the DMRG ground state. [1] S. Yan, D. A. Huse, and S. R. White, Science 332, 1173 (2011). [2] Y.-m. Lu, Y. Ran, and P. Lee, Phys. Rev. B 83, 224413 (2011). [3] Hermele et. al. Phys. Rev. B, 77, 224413 (2008).

Poster 33

Exotic phases in the frustrated hexagonal lattice

Daniel C. Cabra

Departamento de Física Universidad Nacional de La Plata

We study the phase diagram of the Heisenberg model on the Honeycomb lattice with

antiferromagnetic interactions up to third neighbors along the line J2=J3, close to the point where it has macroscopic degeneracy at the classical level. Using the Schwinger boson technique followed by a mean field decoupling and exact diagonalization for small systems we find an intermediate phase with a spin gap and short range Neel correlations even in the strong quantum limit 1/2.

We have also studied the magnetization curve for J3=0, close to J2/J1 = 1/2 where the classical ground state is also highly degenerate. The properties of the magnetization curve and phase transitions are studied by means of Montecarlo, which shows many interesting transitions.

Poster 34

Enhanced Quasi-One-Dimensionality of SmNiC2 by Pressure and its Effect on Charge Density Waves

Jae Nyeong Kim and Ji-Hoon Shim

Department of Chemistry, Pohang University of Science and Technology, Pohang 790-784,

Korea

We have investigated the electronic structures and the Fermi surface properties of SmNiC2 and their effects on the charge density wave (CDW) transition using a first principles calculation. In the ambient pressure and paramagnetic (non-magnetic) ground state, the Fermi surface (FS) and the calculated generalized susceptibility show the prominent FS nesting feature along q1=(0.5, 0.52, 0). We also found that the sizes of nesting features are very sensitive to the change of magnetic ordering or volume. In a ferromagnetic ground state, split bands by exchange interaction suppress the FS nesting feature and destroy CDW phase. With increasing pressure, the nesting vector q1 is gradually shifted to q1=(0.5, 0.56, 0) at 14 GPa. Also, qR=(0.5, 0.5, 0.5), which is almost saddle point in ambient pressure, becomes prominent local maxima. Our calculation supports that both q1 & qR vector have multiple CDW transition under the pressure.

Poster 35

Correlation-Induced Non-Stoner type Metallic Ferromagnetism of One-Dimensional Transition Metal

Chains

Hanhim Kang, Geunsik Lee, P. Dua, Ji-Hoon Shim, and Kwang S. Kim

Department of Chemistry, Pohang University of Science and Technology, Korea.

We investigated the one-dimensional monomer chain of 3d transition metals (Fe, Co, and Ni) by ab-initio band structure calculation with quasiparticle GW method [1]. The band width of Fe monomer chain showed clear spin-dependency, which can not be included by the LDA method. We confirmed that the spin-dependency of band width of the one-dimensional Fe monomer chain is due to the correlation effects such as pair hopping interaction by the extended Hubbard model study [2][3]. In the model study, we observed that the pair hopping-induced spin-dependency of the band structure can be enhanced if the system is nearly half-filled and in low dimension. The conclusion clearly explains why only the Fe monomer chain, which has occupancy near half-filled, shows the spin-dependent band width, rather than Co and Ni, which have occupancy far from half-filled. [1] Takao Kotani et al, Phys. Rev. B 76, 165106. [2] J. E. Hirsch, Phys. Rev. B 43, 705. [3] J. E. Hirsch, Phys. Rev. B 59, 6256.

Poster 36

Observation of orbital angular momentum from t2g-states of Sr2RuO4.

Wonsig Jung1, Wonshik Kyung1, Beomyoung Kim1, Yoonyoung Koh1,Chul Kim1, Soohyun

Cho1, Masashi Arita3, Kenya Shimada3, Yoshida Yoshiyuki1 and Changyoung Kim1,*

1Institute of Physics and Applied Physics, Yonsei University, Seoul, Korea 2 National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki

305-8568, Japan 3Hiroshima Synchrotron Radiation Center, Hiroshima University, Higashi-Hiroshima,

Hiroshima 739-0046, Japan

We observed electronic structure of superconducting material, Sr2RuO4 with angle-resolved photoemission spectroscopy using circular dichroism(CD) method to investigate its orbital character. In this results, we observed large circular dichroism character and it shows complicated orbital structure of Sr2RuO4. CD signal comes from obital angular momentum revealed by inversion symmetry breaking at cleaved surface. We will perform the same work for rhodate and iridate samples to compare 3-, 4- and 5-d orbitals.

Poster

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Poster 38

Magnetic moment orderings of Fe atoms in Fe-intercalated TiX_{2} (X=S, Se)

Seung Ill Hyun and J.h. Shim

Department of Chemistry, POSTECH, Korea

Titanium dichalcogenides shares the same layered structure, except TiO2. Their physical

properties, however, are different from each other. TiSe2, for example, is the only compound that bears an unconventional charge-density wave (CDW) transition under 200K, whereas the others show no distinct structural distortion.[1] Furthermore, Iron-intercalated TiS2 and TiSe2 exhibit different types of magnetism. Fe0.5TiS2 displays a ferromagnetic ordering under 80K, Fe0.5TiSe2 shows an antiferromagnetic ordering under 135K.[2,3] In order to describe the magnetic interactions between Fe atoms, we apply the first principle calculation on Fe0.5TiX2 (X=S, Se) and explain the experimental observations correctly. We also discuss the origin of different magnetic behaviors based on the structural & elemental effect. [1] K. C. Woo, F. C. Brown, W. L. McMillan, R. J. Miller, M. J. Schaffman, and M. P. Sears,

Phys. Rev. B 14, 3242 (1976) [2] N. V. Selezneva, N. V. Baranov, V. G. Pleshchev, N. V. Mushinikov, and V. I. Maksimov,

Phys. Solid State 53 (2), 329 (2011) [3] N. V. Baranov, V. G. Pleshchev, E. M. Sherokalova, N. V. Selezneva and A. S. Volegov,

Phys. Solid State 53 (4), 701 (2011)

Poster 39

Observation of orbital angular momentum of topological insulator

Wonsig Jung1, Yeongkwan Kim1, Beomyoung Kim1, Yoonyoung Koh1, Chul Kim1,

Masaharu Matsunami2, Shin-ichi Kimura2, Masashi Arita3, Kenya Shimada3, Jung Hoon Han4, Juyoung Kim5, Beongki Cho5, and Changyoung Kim1,*

1 Institute of Physics and Applied Physics, Yonsei University, Seoul, Korea

2 UVSOR Facility, Institute for Molecular Science and Graduate University for Advanced Studies, Okazaki 444-8585, Japan

3 Hiroshima Synchrotron Radiation Center, Hiroshima University, Higashi-Hiroshima, Hiroshima 739-0046, Japan

4 Department of Physics, Sungkyunkwan University, Suwon, Korea 5 School of Physics and Department of Materials Science and Engineering, GIST, Gwangju

500-712, Korea

We performed angle resolved photoemission (ARPES) studies on topological insulator with circularly polarized lights. The ARPES data show very strong circular dichroism, indicating existence of orbital angular momentum (OAM). Moreover, the alignment of OAM is found to have a strong binding energy dependence. Such energy dependence comes from a relatively strong band warping effect in Bi2Te3 compared to Bi2Se3. OAM close to Dirac point has an ideal chiral structure sin(x). As the binding energy decreases, warping effect comes in and circular dichroism along the constant energy contour cannot be explained by a simple sin(x) function but requires a sin(3x) term. Such behavior is found to be compatible with the theoretically predicted spin structure. When the warping effect becomes even stronger near the Fermi energy, circular dichroism has sin(6x) symmetry.

Poster 40

Edge State of the Topological Insulator in a Graphene Structure

Hyeonjin Doh1 and Gun Sang Jeon2

1 Dept. of Physics, Konkuk University, Seoul 143-701, Korea

2 Dept. of Physics, Ewha Womans University, Seoul 120-750, Korea

We investigate the edge state of the Quantum Spin Hall effects which appears in a honeycomb lattice described by the Kane-Mele (KM) model. It is well known that the KM model with a finite spin-orbit interaction demonstrates a two-dimensional topological insulator which shows an insulating gap in a bulk state with a metalic state on the boundary. This metalic edge state is attributed to the Z2 topological nature of the system and is protected by the time reversal symmetry. By using the Harper's equation derived from the Schrödinger equation of the KM model, we develop an analytical approaches for this edge state which has been studied mostly in numerical approaches. We consider a graphene ribbon structure with spin-orbit interaction and sublattice pottential. We obtain the explicit dependence of the localization and the energy dispersion of the edge state on the momentum and spin-orbit interaction. In particular, we study the variation of the localization length of the edge state and its implication in the nanoribbons.

Poster 41

Epitaxial graphene on heavily-ion-implanted 6H-SiC surfaces

J. Seoa, H. Shina, J. Parka, J. R. Ahna,b

a BK21 Physics Research Division, Sungkyunkwan University, Suwon 440-746, Republic of Korea

b SKKU Advanced Institute of Technology (SAINT), Sungkyunkwan University, Suwon 440-746, Republic of Korea

Graphene, a two-dimensional sheet of sp2-bonded carbon arranged in a honeycomb lattice

has attracted significant attention due to its interesting characteristics such as high carrier mobility, optical transparency, mechanical strength, and possible applications in various fields. Among the techniques developed for producing graphene, epitaxial growth on silicon carbide (SiC) is a promising method for large-scale production. Ion implantation is also a mature technology in large-scale electronic industry, which can take the epitaxial graphene into the semiconductor foundries. Here we studied post ion-implant growth of epitaxial graphene on 6H-SiC substrates

according to ion fluences, acceleration voltages, and substrate temperatures. N+ ions at 40-145keV were implanted with fluences of 1×1017 N+/cm2 and 3×1017 N+/cm2 into 6H-SiC substrates under room temperature (RT) and 650°C. The ion distributions and structural variations in the implanted samples have been studied using secondary ion mass spectrometry (SIMS) and transmission electron microscopy (TEM) both before and after the graphene growth. This study revealed that the implanted N+ ion distributions in 6H-SiC are robust up to ~1330°C at which the epitaxial graphene begins to grow on Si-face of 6H-SiC and the graphene is formed only when the substrates are maintained at 650°C during ion implantation.

This is believed to be due to the prominent damage recovery of 6H-SiC in high temperature implantations. The high crystallinity of the epitaxial graphene grown on the damage-recovered 6H-SiC was confirmed by photoelectron spectroscopy and low-energy electron diffraction.

Poster 42

Growth of epitaxial graphene on patterned SiC and transfer onto patterned substrates.

Ji-Hoon Park, Hyeon-Jin Shin,* Jae-Young Choi, and Joung Real Ahn*

BK21 Physics Research Division, Sungkyunkwan University, Suwon, 440-746, Republic of

Korea

Recent development of large area graphene synthesis on metal layer by chemical vapor deposition (CVD) or epitaxial growth on silicon carbide (SiC) opened the possibility for applications such as transparent electrodes for ITO replacement. For instance, graphene has been demonstrated for use in a liquid crystal display (LCD) and/or organic light emitting diode (OLED) test cell as a bottom electrode. However, the actual device, e.g., an active-matrix (AM) LCD, operates by switching individual elements of a display, using a thin-film transistor (TFT) for each pixel. Here, the pixel electrode of a display should extend down to the transistor’s source or drain, thereby making contact with a via hole, which demands that a three-dimensional (3D) architecture electrode be deposited on a flat surface as well as its side walls. Although large-area graphene growth can be applied for a wide range of applications, 3D graphene architecture growth has not been realized for actual devices due to the original limitation of planar graphene growth. Herein, we demonstrate for the first time 3D graphene architecture growth and its facile transfer to a planar and/or 3D substrate. To prevent agglomeration of nano-scale metal catalyst by the CVD process, we chose a SiC system. Graphene, a few layers thick, was epitaxially grown on a pre-patterned SiC substrate with nano-size thickness which was produced by photolithography and dry etching. Graphene on a vertical facet of the SiC pattern with a few-hundred nanometers in height was perfectly prepared using this approach, contrary to the CVD method. Furthermore, we suggest the use of a facile transfer method of graphene on SiC to a SiO2 substrate using thermal release tape after hydrogen intercalation. In spite of the troublesome transfer issue of SiC, the geometry of the 3D graphene was perfectly transferred onto the planar SiO2 as well as the 3D SiO2 structure. In other words, the 3D graphene architecture was maintained as a floating cap structure on planar SiO2 and the vertical facet of the 3D SiO2 structure was well covered. Moreover, the graphene bottom layer without a 3D cap and the inverted bowl structure in the 3D graphene architecture were selectivly transferred by controlling intercalation and pressure. These approaches could provide a beneficial method for preparing a 3D graphene architecture as well as for modifying the ordered structure to be utilized in real devices.

Poster 43

Palladium silicidation and intercalation-induced epitaxial growth of charge neutral quasi-free-standing monolayer

graphene on a Si-face of 6H-SiC

Hacheol Shin, Inkyung Song, Chong-Yun Park, Joung Real Ahn

Sungkyunkwan University, Republic of Korea

Intrinsic high mobility of graphene are much reduced in graphene devices by various factors. Two critical factors degrading mobility are uniformity in an atomic structure such as number of a layer and an interaction with a substrate. Recently Shuai-Hua Ji et al. reported quantitatively that conductivity is much reduced by one sixth when electrons pass through a boundary between monolayer and bilayer graphene at a step edge in comparison to conductivity of monolayer graphene. This suggests that uniformity of number of graphene layer is a more crucial factor than expected. In particular, in epitaxial graphene on SiC, the uniformity of number of layer is an intrinsic and serious problem because Si is more rapidly sublimated near a step edge in the formation of epitaxial graphene by thermal evaporation of Si and, subsequently, epitaxial graphene with different layers coexists intrinsically on a terrace. Another factor degrading mobility is an interaction between graphene and a substrate. In epitaxial graphene, the interaction was reduced by intercalation of metal or molecule such as H, F, and Au between graphene and a substrate, which results in quasi freestanding graphene. Various charge neutral quasi freestanding graphene has been reported, but the charge neutrality was found at an optimal coverage of an intercalated element and annealing temperature. This makes it difficult to achieve spatially homogeneous charge neutrality of quasi freestanding graphene, and a method with a broad range of coverage and temperature is demanded. We demonstrate that charge neutral quasi freestanding monolayer graphene can be grown uniformly without coexistence of a buffer layer and a bilayer graphene which limit mobility of epitaxial monolayer graphene. Because coexistence of two different phases is inevitable on a SiC surface, uniform monolayer graphene was produced based on two different phases, a Si-rich phase and a C-rich phase called a buffer. Pd was deposited on both the Si-rich and C-rich phases and annealed up to 900 ◦C. The Si-rich phase produced Pd silicide and charge neural quasi freestanding monolay graphene was produced on the Pd silicide while, on the C-rich phase, Pd was intercalated between the buffer layer and SiC resulting in charge neutral quasi freestanding monolayer graphene, where the quasi freestanding monolayer graphene on two difference regions was connected atomically. The combination of Si silicidation and intercalation result in uniform charge neutral quasi freestanding uniform monolayer on a SiC surface, where the electronic and atomic structures were observed using angle-resolved photoemission spectroscopy and scanning tunneling microscopy.

Poster 44

Ru-doped La0.6Sr0.4MnO3 Thin Film as a Coercivity Tunable Material Studied by X-ray Magnetic Circular Dichroism

T. HaranoA, K. IshigamiB, V. K. VermaA, G. ShibataA, T. KadonoA, A. FujimoriA,C,

K. TakedaC, T. OkaneC, Y. SaitoC, H. YamagamiD, H. YamadaE, A. SawaE, M. KawasakiF,

Y. TokuraF, A. TanakaG

A Department of Physics, Graduate School of Science, The University of Tokyo B Department of Complexity Science and Engineering, Graduate School of Frontier Sciences,

The University of Tokyo C Quantum Beam Science Directorate, Japan Atomic Energy Agency (JAEA)

D Department of Physics, Graduate School of Science, Kyoto Sangyo University E Correlated Electron Heterointerfaces Group, Nano electronics Research Institute, National

Institute of Advanced Industrial Science and Technology (AIST) F Department of Applied Physics, School of Engineering, The University of Tokyo

G Department of Quantum Matter, Graduate School of Advanced Sciences of Matter, Hiroshima University

La1-xSrxMnO3 (LSMO) is a typical half-metallic compound and shows spin and orbital

orders upon substitution of Sr for La (hole doping). Although LSMO is attracting attention for the possible application to magnetic tunnel junctions, there is a serious problem that the coercivity (HC) is too small. Yamada et al. reported that one can enhance the coercivity by substituting Ru for Mn [1], and attributed this effect to antiferromagnetic coupling between Mn and Ru and charge transfer from Mn4+ to Ru4+ (Mn4++Ru4+→Mn3++Ru5+). In order to obtain information about the electric and magnetic states of each element in this system and to elucidate the mechanism of the coersivity enhancement, we performed x-ray magnetic circular dichroism (XMCD) measurements. We could measure the spectra of Mn and those of Ru separately because XMCD is an element-specific experimental probe. The XMCD spectra of Mn L-edge and Ru M-edge are shown in Fig. 1. One can conclude that the spin direction of Mn is opposite to that of Ru consistent with Yamada et al. [1] . By applying the XMCD sum rules, we found that the orbital moment of Ru is finite and is parallel to the spin moment. This indicates that Ru 4d orbitals are occupied by more than 5 electrons and that that the valence of Ru is 3+. [1] H. Yamada et al., Appl. Phys. Lett. 86, 192505 (2005)

Fig. 1 XMCD spectra of Mn L-edge and Ru M-edge

Poster 45

Electrical and magnetic phase transition characteristics of VO2 thin flims grown on GaN substrate

Hyoung Woo Yang1, Junginn Sohn2, Seung Nam Cha2, Jong Min Kim2 and Dae Joon Kang1*

1 Department of Energy Science, BK21 Physics Research Division, Institute of Basic Science,

Sungkyunkwan University, Suwon 440-746, South Korea 2 Frontier Research Lab., Samsung Advanced Institute of Technology, Korea.

We report on the synthesis of high-quality VO2 thin films grown on GaN/Sapphire

substrates by RF sputtering and their unique metal-insulator transition (MIT) properties. The electrical and magnetic properties in VO2 thin films grown on GaN are shown to be markedly different metal insulator transition behavior from the case of conventional VO2 thin film system as reported before. The VO2 thin film grown on GaN substrate exhibited the metal insulator transition behavior, which was known to be observed only either in doped sample or under uniaxial stress. The VO2 thin films grown on GaN substrate show higher crystallinity and larger resistance change across MIT compared to those grown on c-cut sapphire substrate. Raman spectra indicated that metal insulator transition occurred directly from monoclinic M2 to rutile R phase with increasing temperature. Large lattice mismatch between VO2 and GaN substrate is attributed to cause M2 phase to be thermodynamically stable. Besides, an abrupt transition from a high-temperature magnetic phase to a low-temperature one, with quite distinct magnetic correlation strengths, was observed. This study may lead to a unique opportunity to better understand the mechanism of electrical and magnetic phase transition in VO2.

Poster 46

Study on Cu2ZnSnS4 thin films prepared by Pulsed Laser Deposition method

Seokbae Lee1, Ilho Jung1, Jongsung Bae2 and Jungseek Hwang1

1 Department of Physics, Sungkyunkwan University, Suwon 440-746, Republic of Korea

2 Busan Center, Korea Basic Science Institute, Busan 609-735, Republic of Korea

Polycrystalline Cu2ZnSnS4 (CZTS) thin films have been directly deposited on heating

Mo-coated glass substrates by a Pulsed Laser Deposition (PLD) technique. From scanning electron microscope (SEM) measurements we observed that the sizes of particles are dependent of the substrate temperature (Tsub); the size of particles is getting larger as the temperature increases. We also observed that the thicknesses of samples are getting thinner as Tsub increases; we suspect that the sulfur and tin molecules become more volatile with increasing Tsub. From both measurements using X-ray diffraction (XRD) and Raman spectroscopy we found that CZTS thin films are formed with Tsub range from 200 to 400 oC. We achieved the best quality of sample with near Tsub = 300 oC. The presence of the Cu2-xS impurity phase in CZTS thin films with Tsub=300 and 350 oC implies that there are Cu-rich regions in these CZTS thin films. We determined the bandgaps (Eg) of CZTS thin films by optical spectroscopy measurement. We observed Tsub dependence in the bandgap. Further studies might be necessary to sort out some important issues: Tsub dependent thickness, Tsub dependent bandgap, presence of Cu2-xS impurity phase and so on. * J.S. Bae acknowledges research fund supported by KBSI grant (T32613).

Poster 47

Selective Band Engineering of an Isolated Subnanometer Wire

I. Song, D.-H. Oh, C.-Y. Park, and J. R. Ahn

Sungkyunkwan University, Republic of Korea

Band engineering has been achieved mainly by substituting an atom of a pristine

nanomaterial with an extra atom. At the ultimate nanometer scale, subnanometer scale, a nanowire becomes closer to an ideal 1D system and the band engineering by the atomic substitution enters a different regime. The strong disorder by the atomic substitution tends to break a pristine 1D system. In the band engineering of the subnanometer wire (hereafter subnanowire), we needs to find a way of circumventing the dilemma of doping and disorder. There is another challenging problem to find out a conclusive experimental proof that its electronic band structure is changed within a single isolated subnanowire. A unique experimental way is to measure its electronic band structure by angle-resolved photoemission spectroscopy (ARPES). Because a photon beam in ARPES measurement cannot be focused down to subnanometer scale, a single subnanowire cannot be used and rather subnanowires have to be aligned along a specific direction on a surface. A fundamental requirement to resolve the puzzling problem is that subnanowires have to be aligned by a self assembly method. In comparison to the atomic structure, its electronic structure is required to be decoupled to observe a 1D electronic structure change of a single isolated subnanowire by a dopant. In this study, self-assembled subnanowires on a stepped surface, Au-induced subnanowires on a Si(553) surface, were chosen. A Si(553) surface, which is one of stepped Si(111) surfaces, has an appropriate terrace width to assemble subnanowires along its step edge direction and its step edge structure can decouple subnanowires electronically. Three different metallic subnanowires exist on its single terrace and each metallic wire has only a single metallic band. After extra Au atoms were adsorbed on the self-assembled subnanowires at room temperature, only one of metallic bands moved rigidly to a higher binding energy without a change in other metallic bands, which was directly observed by ARPES measurement. Here we note that if the three metallic subnanowires are coupled electronically to each other, all of the three metallic bands have to shift rigidly. This experimentally proves that only one of self-assembled multiple metallic wires can be controlled electronically by a dopant and the electronic structure of an isolated wire can be controlled down to a subnanometer scale.

Poster 48

Orbital angular momentum structure of Cu(111) and Au(111) surface states.

Beomyoung Kim1, Choong H. Kim2, Panjin Kim1, Wonsig Jung1, Yeongkwan Kim1, Yoonyoung Koh1, Masashi Arita3, Kenya Shimada3, Hirofumi Namatame3,Masaki

Taniguchi3,Jaejun Yu2, and Changyoung Kim1,*

1 Institute of Physics and Applied Physics, Yonsei University, Seoul 120-749, Korea 2 Department of Physics and Astronomy, Seoul National University, Seoul 151-747, Korea

3 Hiroshima Synchrotron Radiation Center, Hiroshima University, Higashi-Hiroshima, Hiroshima 739-0046, Japan

We performed angle-resolved photoemission studies on Cu(111) and Au(111) surface

states with circularly polarized light to investigate local orbital angular momentum (OAM) structures. Existence of OAM is confirmed, as predicted, to exist in systems with an inversion symmetry breaking. Cu(111) surface state bands are found to have chiral OAM in spite of very small spin-orbit coupling, consistent with the theoretical prediction. As for Au(111), we observe split bands for which OAM for the inner and outer bands are parallel, unlike the Bi2Se3 case. We also performed first-principles calculations and the results are found to be consistent with experimental results. Moreover, the majority of OAM is found to have d-orbital origin while a small contribution comes from p orbitals. An effective Hamiltonian that incorporates the role of OAM is derived and is used to extract the spin and OAM structures. We discuss the evolution of angular momentum structures from a pure OAM system to a strongly spin-orbit-entangled state. We predict that the transition occurs through a reversal of the OAM direction at a k point in the inner band if the system has a proper spin-orbit coupling strength.

Poster 49

Spontaneous-step-selective growth of In nanowires on Si(557): a ideal template to one-dimensional electronic

structures

B. G. Shin1, M. K. Kim1, D.-H. Oh1, C.-Y. Park1,3, and J. R. Ahn1,4

1 BK21 Physics Research Division, Sungkyunkwan University, Suwon 440-746, Republic of Korea

2 College of Pharmacy, Chungnam National University, Daejeon 305-764, Republic of Korea

3 Department of Energy Science, Sungkyunkwan University, Suwon 440-746, Republic of Korea

4 SKKU Advanced Institute of Technology (SAINT), Sungkyunkwan University, Suwon 440-746, Republic of Korea

Atomic wires do not interact directly with each other and are therefore ordered by an

indirect substrate mediated interaction, whereas molecular structures can be assembled spontaneously by a direct interaction with each other. Such interwire interactions were very short and subsequently an interwire distance of ordered atomic wires were a few Å. Because of the interwire interaction, atomic wires have been described as a quasi 1D system rather than an ideal 1D system. Therefore, an atomic wire with a long interwire distance needs to study an ideal 1D system but, as mentioned before, atomic wires were not ordered with a long interwire distance. Assembly of a long interwire distance atomic wire is thus very challenging and demanded to widen experimental scope of studies on one-dimensional physics. In this study, indium atomic wires with a long interwire distance of 5.7 nm were ordered spontaneously at room temperature on a stepwise nanotemplate, a Si(557) surface. In general, interwire interactions are required to produce ordered nanowires so that other ordered atomic wires have a short interwire distance of a few Å, as described above. The long interwire distance of the ordered indium atomic wires is therefore very unique. Indium atoms were mobile at room temperature and were adsorbed on a only specific step among four steps, one (111) and three (112) steps of the reconstructed Si(557) surface, maintaining the stepwise nanotemplate structure, as observed by scanning tunneling microscopy (STM), despite the fact that the triple steps have similar local atomic structures. The energetic stability of the indium atomic wires was calculated by first-principles calculations. The reconstructed Si(557) structure model was based on the dimer-adatom-stacking fault (DAS) model and adatom-parallel dimer (AD) model of (111) and (112) facets, respectively.[1, 2] Total energy differences between indium atomic wires on the three (112) steps was very small and the most stable atomic structure was located at the second (112) step, which was consistent with STM images. STM simulations also reproduced the x2 periodicity of the In-induced atomic wires along the wire direction. [1] K. Takayanaki, Y. Tanishiro, M. Takahashi, and S. Takahashi, J. Vac. Sci. Technol. A 3,

1502 (1985) [2] D. Oh, M. Kim, J. Nam, I. Song, C. Park, S. Woo, H. Hwang, C. Hwang, J. Ahn, Phys.

Rev. B, 77, 155430 (2008)

Poster 50

Metamagnetic transition in Ca1-xSrxCo2As2 (x = 0 and 0.1) single crystals

G. J. Ye, J. J. Ying, Y. J. Yan, A. F. Wang, Z. J. Xiang, P. Cheng, G. J. Ye, and X. H. Chen*

Hefei National Laboratory for Physical Science at Microscale and Department of Physics, University of Science and Technology of China,

We report the magnetic and transport measurements of CaCo2As2 and Ca0.9Sr0.1Co2As2

single crystals.An antiferromagnetic transition was observed at about 70 K and 90 K for CaCo2As2 and Ca0.9Sr0.1Co2As2,respectively. Magnetic and magnetoresistance measurements reveal a metamagnetic transition from an antiferromagnetic state to a ferromagnetic state with a critical field of 3.5 and 1.5 T for these two samples,respectively along the c axis at low temperature. For the field applied along the ab plane, spins can be fully polarized above a field of 4.5 T for Ca0.9Sr0.1Co2As2.While for CaCo2As2, spins cannot be fully polarized up to 7 T. We propose the cobalt moments of these two materials should be ordered ferromagnetically within the ab plane but antiferromagnetically along the c axis (A-type antiferromagnetic).

Poster 51

s-wave superconductivity in barium-doped phenanthrene as revealed by specific-heat measurements

Peng Cheng1, Jianjun Ying1, Xiangfeng Wang1, Yajun Yan1, Ziji Xiang1, Xigang Luo1, Zhe Sun2, and

Xianhui Chen1

1 Hefei National Laboratory for Physical Science at Microscale and Department of Physics, University of Science and Technology of China, Hefei, Anhui 230026, People’s Republic of China

2 National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei,Anhui 230029, People’s Republic of China

Organic materials are believed to be potential superconductors with high transition temperature (Tc). One key feature of the organic superconductors is that they have π-molecular orbitals, and the π-electron can delocalize throughout the crystal, giving rise to metallic conductivity due to a π-orbital overlap between adjacent molecules. Recently we have successfully synthesized superconducting samples such as alkali-metal, alkali-earth metal and rare-earth metal doped Phenanthrene with π-molecular orbitals. In this poster we introduce high-quality Ba-doped phenanthrene superconducting sample with 100% shielding fraction evidenced by ZFC magnetic susceptibility, and measured the specific heat down to 360 mK and a superconducting volume fraction of 86% is inferred from specific heat. The specific-heat data indicate that Ba-doped phenanthrene is a single-gap s-wave superconductor with moderate coupling, and this sets constraints on theoretical models for the understanding of superconductivity in these hydrocarbon superconductors.

Poster 52

Suppression of superconductivity in the Perovskite-type blocking layered (Ca4Al2O6)(Fe2(As1-xPx)2) superconductor

Akira Iyo, Parasharam M. Shirage, Kunihiro Kihou, Nao Takeshita, Hiroshi Eisaki

National Institute of Advance Industrial Science and Technology (AIST), Central-2, 1-1-1 Umezono, Tsukuba, Ibaraki-305 8568, Japan.

A Perovskite-type blocking layered iron-pnictides of (Ca4Al2O6)(Fe2Pn2) are

superconductors for both Pn = As and P with transition temperatures of 28 K and 17 K, respectively. FeAs4 tetrahedrons in the (Ca4Al2O6)(Fe2As2) crystal structure are extremely elongated along c-axis direction due to the smallest a-axis lattice parameters. A substitution of P for the As-site has been carried out expecting an enhancement of Tc, which is based on the idea that FeAs4 tetrahedrons transform towards regular shape that is empirically favorable to higher Tc. Contrary to our expectations, superconductivity is found to disappear in the x range from 0.5 to 0.95 in (Ca4Al2O6-y)(Fe2(As1-xPx)2), which is a striking contrast to BaFe2As2 and BaFe2P2 case where the superconductivity occurs in their solid solution. We also found that samples in the non-superconducting region show resistivity anomalies in the temperature range from 58 K to 97 K. The behavior is reminiscent of the resistivity kink commonly observed in various non-superconducting parent compounds, which signals the onset of antiferromagnetic/orthorhombic long-range order.

Poster 53

Resonant APRES study of NiS2-xSex

Garam Han1, YK Kim1, YY Koh1, BY Kim1, WS Kyung1, Chul Kim1, C. Kim1

1 Institude of Physics and Applied Physics , Yonsei university, Korea

Understanding Metal insulator transition(MIT) is one of the challenging issues in condensed matter physics. NiS2-xSex (NSS) is one of the best known systems for the band width controlled MIT study while most of High-Tc superconductors(HTSCs) are described as band filled MIT. Cubic pyrite NiS2 is known as a charge-transfer (CT) insulator and easily forms a solid solution with NiSe2, which is a good metal while nevertheless being isostrucural and isoelectronic to NiS2. MIT is induced by Se alloying and is observed at low temperature for x=0.45. The important merit is that there is no structure transition which often accompanies MIT. However, even the experimental band dispersion is not known so far along with many controversies. Especially, What charactor of band leads MIT is the crucial role of solving this problem. For this reason, we performed resonant angle resolved photoemission spectroscopy on good quality single crystals and successfully obtained Fermi surface maps of x=0.43(insulating side), x=0.7 and x=2 (metallic side).

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Abstracts for - SKKUphysics.skku.ac.kr/symposium/ichn2012/book.pdf · Abstracts for International Conference on Heavy Electrons and Novel Quantum Phases with A3 Workshop Gyeongju