2018 - 2019 - Institut Néelneel.cnrs.fr/IMG/pdf/brochure_stage_neel_2018_2019.pdf · 2018-09-10 · ASTR-0014-02), your mission will be to develop a new fabrication process of NdFeB

INTERNSHIP

neel.cnrs.fr

2018 - 2019

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NÉEL Institute is a major research laboratory in physics, with about 450 members. Its collective strength is expressed in numerous national and international collaborative projects, in open technological platforms of exceptional quality, and by a remarkable level of scientific production. This booklet presents the internship topics offered by NÉEL researchers. These cover a wide range of scientific and technological fields, reflecting the diversity of our teams. Magnetism, quantum fluids, new materials, crystallography and surface science mingle with quantum nanoelectronics, nanomechanics, non-linear and quantum optics, spintronics, etc. Beyond our core expertise in physics of condensed matter, we also work at the interface with chemistry, engineering, astrophysics and biology. In all these fields, our mainly experimental activity benefits from the local presence of many worldclass experts in theoretical, analytical and computational physics. NÉEL Institute fosters a technological expertise that is essential to bring our research projects to the highest level, through often unique house-made or in house designed instruments. We are also actively involved in creating value from our research in the sectors of electronics, energy, health and space. This booklet contains the Master internship offers for the 2018-19 academic year. Most of them are Master 2 projects, offering often the possibility of going on as a PhD student. If you are starting your Master degree, you will also find Master 1 project proposals. Many of the Master 2 topics may also be adapted to Master 1 projects. You are welcome to a virtual visit of NÉEL Institute through this booklet and our website, www.neel.cnrs.fr. Please get in touch with NÉEL researchers and come around for a real visit ! Etienne BUSTARRET Director, NÉEL Institute September 2019

Institut NEEL-CNRS 25, rue des Martyrs – Bâtiment - BP 166 – 38042 Grenoble cedex 9 – France

+33 (0)4 76 88 74 68 +33 (0)4 76 88 12 30

L’Institut Néel est une unité propre du CNRS conventionnée avec l’Université Grenoble Alpes

http://www.neel.cnrs.fr/

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L’Institut Néel est un grand laboratoire de recherche en physique avec près de 450 membres. Sa force collective s’exprime dans de nombreuses collaborations internationales et nationales, la présence en son sein de plate-formes technologiques ouvertes aux performances exceptionnelles, et un niveau de production scientifique remarquable. Vous trouverez dans ce recueil les sujets de stage proposés par les chercheurs de l’Institut Néel. Les domaines scientifiques et technologiques sont extraordinairement variés, à l’image des activités de nos équipes. S’y côtoient en effet magnétisme, fluides quantiques, nouveaux matériaux, cristallographie, science des surfaces, nano-électronique quantique, nano-mécanique, optique nonlinéaire et quantique, spintronique… Par delà notre cœur de métier qu’est la physique de la matière condensée, nous travaillons aussi aux interfaces avec la chimie, l’ingénierie et la biologie. Dans tous ces domaines, notre activité principalement expérimentale se développe en lien avec de fortes compétences transversales en physique théorique analytique et numérique. L’Institut Néel développe une expertise technologique au plus niveau, essentielle pour mener à bien de nombreux projets de recherche. Enfin, nous nous impliquons activement dans la valorisation de nos recherches et de nos savoir-faire dans les domaines de l’électronique, de l’énergie, de la santé et aussi les sciences de l’univers. Cette brochure regroupe les offres de stage de Master proposés pour l’année universitaire 2018-2019. Ce sont principalement des stages de Master 2 avec pour la plupart une possibilité de continuation en thèse. Si vous commencez votre master, vous trouverez aussi des propositions de stage de Master 1. De nombreux sujets de Master 2 peuvent aussi être déclinés en sujets de Master 1. Je vous souhaite la bienvenue à l’Institut Néel, au moins virtuellement par cette brochure et au travers de notre site web www.neel.cnrs.fr ! N’hésitez pas à contacter les chercheurs de l’Institut Néel afin de nous rendre visite.

Etienne BUSTARRET Director Institut NEEL September 2019

Institut NEEL-CNRS 25, rue des Martyrs – Bâtiment - BP 166 – 38042 Grenoble cedex 9 – France

+33 (0)4 76 88 74 68 +33 (0)4 76 88 12 30

L’Institut Néel est une unité propre du CNRS conventionnée avec l’Université Grenoble Alpes

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NÉEL INSTITUTE Grenoble

Topic for Master 1 internship – Academic year 2018-2019

Table des matières / Contents

Recycling of end of life NdFeB magnets ................................................................................... 9

Flying qubits using ultrashort single-electron charge pulses ................................................... 10

High temperature superconducting oxychlorides: a light element model for cuprates ............ 11

Nouveaux Supraconducteurs .................................................................................................... 12

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Recycling of end of life NdFeB magnets

General Scope:

In the frame of the “Sintermagrec” project, funded by the French National Research Agency (ANR-17-

ASTR-0014-02), your mission will be to develop a new fabrication process of NdFeB magnets from

recycled NdFeB magnets collected in urban mines. In the proposed process, sintered magnets collected

in WEEE (Waste of Electrical and Electronic Equipments) are, first, pulverised into NdFeB powders.

In a second step, the development of non-conventional sintering techniques using the powder opens up

an interesting valorization perspective. Thus, within the framework of the proposed study, attention will

be given to study the influence of the processing parameters on the induced microstructure and on the

final magnetic properties

As part of the team, you will conduct the tests (heat treatments, milling, DRX, microscopy, etc…), exploit

the results, report on the results (both written and oral reports).

Research topic and facilities available

In CNRS/ Néel Institute, you will benefit from the expertise of the TEMA group

(Processing Elaboration Materials Applications, 6 persons) on the development of processes

using intense magnetic fields, on the recycling processes as well as on the synthesis of alloys

in various forms. Facilities available in the group include high superconducting magnets, various processing tools

(induction cold crucible, furnaces, milling facilities, separation tools, etc…) and characterization devices

(laser granulometry, ATD/TGA, microscopy, etc…). All common facilities from Institut Néel available

as well (SEM, magnetic measurements, DRX, etc…)

Possible collaboration and networking: This subject is part of the "Sintermagrec” project, which involves both academic and industrial

contacts.

Required skills:

-Interest in the recycling and the valorization of by-products.

-General curriculum with a specialty in Materials Science.

-Autonomy, initiative and ability to work in a team and to adapt to a collaborative project, which

includes partners from academic research and industry.

-Knowledge in physicochemical processes and/or metallurgy is welcome.

Starting date: Spring 2019

Contact:

Sophie RIVOIRARD, Institut Néel - CNRS

Phone:04 76 88 90 32 e-mail:[email protected]

More information: http://neel.cnrs.fr

http://neel.cnrs.fr/

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Flying qubits using ultrashort single-electron charge pulses

General Scope: Coherent manipulation of single electrons in solid-state devices is attractive for

quantum information purposes because they have a high potential for scalability. Depending on the

system used, the charge or the spin may code binary qubit information. A particular appealing idea is to

use a single flying electron itself as the conveyor of quantum information. Such electronic flying qubits

allow performing quantum operations on qubits while they are being coherently transferred. Information

processing typically takes place in the nodes of the quantum network on locally controlled qubits, but

quantum networking would require flying qubits to exchange information from one location to another.

It is therefore of prime interest to develop ways of transferring information from one node to the other.

The availability of flying qubits would enable the possibility to develop new non-local architectures for

quantum computing with possibly cheaper hardware overhead than e.g. surface codes.

Research topic: The aim of the proposed M2 internship is to develop a flying qubit architecture using

ultra-short single-electron charge pulses. In order to generate such ultra-short electron wave packets,

we will leverage on the progress made on THz photon production and use photon to electron conversion

devices to engineer THz electronic charge pulses that can be used in quantum nanoelectronics.

Fig.1: A flying electron generated above the Fermi Sea and propagating in an electron waveguide.

References:

Hermelin et al., Nature 477, 435 (2011); Bertrand et al, Nature Nanotech. 11 672 (2016)

Dubois et al., Nature 502, 659 (2013); Roussely et al. Nature Com. 9, 2811 (2018)

Possible collaboration and networking: This project is realized in close collaboration with the

nanoelectronics group in Saclay (C. Glattli), the THz laboratory of the Université de Savoie Mont-Blanc

(J.F. Roux & J.L. Coutaz), the theory group of CEA Grenoble (X. Waintal) as well as the Quantum

Metrology group (AIST), Tsukuba, Japan (S. Takada)

Required skills:

The candidate should have a good background in quantum mechanics and solid-state physics.

Starting date: anytime

Contact:

BAUERLE Christopher

Institut Néel – CNRS, Grenoble

e-mail: [email protected]

web: http://neel.cnrs.fr

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High temperature superconducting oxychlorides: a light element model for cuprates

General Scope:

Cuprates were discovered in 1986 to show superconductivity at the highest temperature at ambient

pressure, a record they still detain (see figure 1), but their phenomenology apparently cannot be grabbed

by present theory, so that they are considered among the main unsolved problems in physics today. In

this context, the discovery of the Na and vacancy doped Ca2CuO2Cl2 oxychloride is very promising

indeed to bridge the gap between theory and experiment since it: lacks high Z atoms; has a simplest

crystalline structure for cuprates, stable at all doping and temperatures; and has a strong 2D character

due to the replacement of apical oxygen with chlorine. Therefore, advanced calculations that incorporate

correlation effects, such as quantum Monte Carlo are easier, but relatively little is known about

Ca2CuO2Cl2 from an experimental point of view. We are now filling this gap by a comprehensive

experimental study covering the whole phase diagram, in particular of the magnon and phonon

dispersion, using advanced approaches based on synchrotron radiations.

Figure 1: Cuprates allows exploiting magnetic

levitation above the liquid Nitrogen temperature,

as shown in the picture (Mai-Linh Doan wikimedia

commons, © Creative commons).

Research topic and facilities available: The internship will focus on the growth and characterisation of single crystal of doped Na doped

Ca2CuO2Cl2 oxychloride, Ca2-xNaxCuO2Cl2 using the large volume press available at the institute (pole

X'Press), their crystalline and crystalline (x-ray diffraction) and superconducting (magnetometry)

characterisation, as well as preparation to adapt the sample for advanced spectroscopic measurements

using synchrotron light.

Possible collaboration and networking: Sample synthesis will be made in collaboration with the group of Prof. I. Yamada (Univ. of Osaka,

Japan).

Required skills:

Background in electronic properties of materials and some basic knowledge of chemistry for material

science.

Starting date: From winter to spring 2019

Contact:

Name: D'ASTUTO Matteo

Institut Néel - CNRS

Phone: (+33)(0)4 76 88 12 84 e-mail: [email protected]



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Nouveaux Supraconducteurs

Cadre général : Les supraconducteurs sont des matériaux aux propriétés étonnantes. Ils sont connus

pour permettre de faire léviter un aimant, ou de léviter sur un aimant voire les deux (Cf. figure). Ils sont

aussi le siège de propriétés quantiques à la pointe de la recherche actuelle. Nous avons découvert

récemment deux nouvelles familles de supraconducteurs, une famille que l’on dit non-conventionnelle

car la supraconductivité coexiste avec un état magnétique et une famille qui allie cet état quantique avec

des propriétés de structure étonnante (ultra-dureté, auto-réparation de la surface).

Ce stage a pour objet l’étude de ces nouvelles familles de supraconducteurs par différentes techniques

expérimentales de pointe.

Sujet exact, moyens disponibles : Après la découverte d’un état supraconducteur dans la famille de

supraconducteurs à base de Fe (LaFeSiH composé), l’intérêt de la communauté scientifique se porte sur

les propriétés quantiques de ce système et de toute la famille (variation de la composition par dopage).

L’étudiant(e) entreprendra des études sur les nouveaux composés à pression ambiante et sous pression.

Il/elle étudiera le lien entre supraconductivité et magnétisme ainsi que transformation structurale.

L’autre famille de supraconducteurs aux propriétés structurales étonnantes a été découverte encore plus

récemment. A priori, le mécanisme d’établissement de l’état supraconducteur fait intervenir les phonons.

L’étudiant(e) caractérisera les phonons par différentes techniques optiques et spectroscopie de pointe.

Expériences : cryogénie, haute pression, transport, susceptibilité magnétique, spectroscopies optiques.

Interactions et collaborations éventuelles : Ce stage s’insère dans un projet ANR (coll. Bordeaux,

Caen, différentes équipes à l’Institut Néel dont théorie). Collaboration avec l’université de Paris 13.

Formation / Compétences : Physique de la Matière condensée, curiosité et goût pour les expériences

délicates.

Période envisagée pour le début du stage : mars-mai 2019

Contact : Méasson Marie-aude / Matteo d’Astuto

Institut Néel - CNRS : [email protected] / [email protected]

Plus d'informations sur : http://neel.cnrs.fr

SC

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aimant

mailto:[email protected]

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Table des matières / Contents Recycling of end of life NdFeB magnets ................................................................................... 9



Nouveaux Supraconducteurs .................................................................................................... 12

“Seeing” frustration in two-dimensional molecular lattices .................................................... 17

Glass Nanomechanical Resonators in the Quantum Ground State .......................................... 18

Development of a Demagnetization Stage for Sub-mK cooling .............................................. 19

Spectroscopic study of free, only optically trapped nanorods ................................................. 20

Coupling a single quantum dot to a mechanical oscillator ....................................................... 21

Studying electrical properties of nanowires by in-situ electron holography ............................ 22

Investigating Multiferroïcity in Doubly Ordered Perovskites.................................................. 23


Growth and redox reaction at the transition metal monoxide/metal interface ......................... 25

Properties of magnetic tunnel junctions with a spin-filtering layer ......................................... 26

STM/STS studies of two-dimensional semiconductors doped with magnetic atoms. ............. 27

Functionalization of suspended thermoelectric nano-generators ............................................. 28


Epitaxial growth of hybrid nanowires for topological quantum computing ............................ 30

Quantum circuits and the Superconductor-Insulator transition ................................................ 31

Wannier Resonances and Two-Frequency Problems in Three-Terminal Josephson Junctions32

Cavitation at the nanoscale ....................................................................................................... 34

Testing the Classical Nucleation Theory ................................................................................. 35

Guided interactions with rare-earth luminescent centers for quantum information processing

.................................................................................................................................................. 36

Theoretical study of excitations in the magneto-electric RMn2O5 compounds ...................... 37

Elaboration of Ln3+-doped α-La(IO3)3 thin films ..................................................................... 38

DNA Nanostructure programming ........................................................................................... 39

Nano-Neuroelectronics ............................................................................................................. 40

Ultrasensitive force measurements at the Quantum/Classical interface .................................. 41

Turbulence Quantique & Vortex .............................................................................................. 42

Superconducting Higgs mode in Monolayer systems under extreme conditions .................... 43

Search for new high Tc superconducting oxides ..................................................................... 44

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New Superconductors with Iron ............................................................................................... 45

Superconducting quantum devices with topological edge channels ........................................ 46

Localized Cooper-pairs in disordered superconductors ........................................................... 47

Search for new high Tc iron-based superconductors ............................................................... 48

Search for superconductivity under pressure in mono and bi-layer graphene ......................... 49

Degradable organosilica nanoparticles for controlled drug delivery ....................................... 50

Controlled nucleation and growth of molecular nanocrystals for biophotonics and advanced

solid-state NMR ....................................................................................................................... 51

White phosphors for LED lighting prepared by sol-gel method .............................................. 52

Molecular spin devices for quantum processing ...................................................................... 53

Interfacing molecular spins with nanomechanical oscillators in the quantum regime............. 54



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“Seeing” frustration in two-dimensional molecular lattices

General Scope: Implementing complexity in lattices of objects is a fascinating goal in physics, holding

promises for the discovery of new states of matter with unique properties. One strategy is the search for

lattices with complex tilings, such as those predicted centuries ago by Archimedes and Kepler.

Strikingly, it is only today that these predictions find practical realizations at the nanometer scale.

Another strategy is to use unit objects having more than a single state on the lattice sites, and whose

mutual interactions prevent them minimizing simultaneously all their pairwise interaction energies. We

then say that the system is frustrated. This frustration is linked to the lattice topology, and can be found

in various systems, such as H2O ice or in certain charge and spin lattice models.

Recently, direct visualisation of frustrated spin lattices has proven to be particularly insightful, revealing

intriguing and exotic phenomena. For example, in micrometer-scaled lattices of magnetic dipoles, we

observed magnetic phases being at the same time liquid and solid [1], and other phases apparently

violating the third law of thermodynamics [2]. Based on these results, we now want to launch a new

research track, and address frustration effects at a much smaller (nanometer) scale and in nonmagnetic

systems. More precisely, we would like to investigate the properties of certain two-dimensional

molecular lattices through their real space imaging (using scanning tunneling microscopy). Molecular

systems present the advantage of being tunable with “turning knobs” that are not accessible in larger-

scale systems: in particular, temperature allows to make them fluctuate, and local electrostatic potentials

applied under the metal tip of the microscope allow us to create point lattice defects at will or to excite

the system locally.

[1] B. Canals et al. Nature Communications vol.7, p.11446 (2016)

[2] Y. Perrin, B. Canals, N. Rougemaille. Nature vol.540,

p.410 (2016)

Research topic and facilities available: The student will

fabricate lattices of C60 buckyballs onto a metal surface. We

expect the formation of triangular lattices (with 1 nm lattice

constant) where each C60 buckyball can have two possible

heights (see figure) due to repulsive interactions between

neighboring molecules. There is a direct analogy between this

C60 lattice and a triangular lattice made of Ising spins coupled

antiferromagnetically (i.e., “up” and “down” spins

preferring to align in opposite directions). The goal of this

project is to image C60 lattices using scanning tunneling

microscopy, and to characterize their “magnetic”

configuration (red / blue arrangement in the figure) based on

frustrated spin models. In a second step, defects will be

intentionally introduced in the lattices to investigate the impact of structural disorder.

Possible collaboration and networking: The work relies on a collaboration between several

researchers at the Néel Institute, experts in the physics of frustrated systems and in the preparation of

atomic and molecular lattices on surfaces. The student will be thus involved in a team work and will

benefit from strong technical support.

Possible extension as a PhD: Yes.

Required skills: Condensed matter physics and / or nanosciences.

Starting date: March, 2019

Contact:

Name: Johann Coraux, Nicolas Rougemaille

E-mail: [email protected] ; [email protected]


Triangular lattice of C60 molecules,

with part of the molecules (red) located

higher than the other (blue).






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Glass Nanomechanical Resonators in the Quantum Ground State

Context:

Keywords: Quantum engineering, two-level systems, glass

Highly motivated students are sought for an ERC-funded project devoted to identifying the

universal low energy excitations of glass. These excitations, thought to be two level systems (TLSs)

formed by atoms or groups of atoms tunneling between nearly equivalent states, will be probed on the

individual level for the first time. This will allow us to make a microscopic test of the controversial

“tunneling model” of glass.

Objectives and means available:

In order to access individual TLSs, a glass nanomechanical resonator will be cooled to its

quantum ground state around 1 mK. Only a few research groups worldwide have succeeded in

cooling a mechanical resonator to the ground state, and most of them use active cooling schemes in

which only the mechanical mode of interest is cold. In contrast, we will draw on our expertise in ultra-

low temperature measurements to cool the entire mechanical resonator to 1 mK.

Ultimately, we are interested in properties of quantum matter. In particular, the identity of the

TLSs will be investigated by making the first measurements of individual TLSs inside a mechanical

resonator. The quantum state of the resonator will be controlled using a qubit to enable these

measurements. First we will look for a signature of an individual TLS in spectroscopic measurements

of the ground-state glass resonator. Then we will use quantum control of the mechanical resonator to

in turn control and measure the quantum state of the TLS. This will yield information about the TLS

and a test of the “tunneling model” mentioned above.

Figure: Intrinsic tunneling two level systems (TLSs) inside a glass nanomechanical resonator. The mechanical

resonator will be cooled to the quantum ground state to enable measurements of the individual TLSs.

Possible collaborations and networking: This work may involve collaboration and interactions with researchers at the Institut Néel,

elsewhere in Europe and in the United States.

Required profile:

The student should have a strong interest in fundamental research and making challenging

measurements at very low temperatures, as well as a thorough understanding of quantum theory at the

Master’s Degree level.

Ce stage pourra se poursuivre par une thèse financée.

Période envisagée pour le début du stage : Flexible

Contact : Andrew Fefferman

Institut Néel - CNRS : 04.76.88.90.92 [email protected]

Plus d'informations sur : http://neel.cnrs.fr/spip.php?rubrique69&lang=fr



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Development of a Demagnetization Stage for Sub-mK cooling

General Scope: The Grenoble Ultra-Low Temperatures group cools

condensed matter samples to sub-mK temperatures to probe fundamental

questions in quantum mechanics. These samples include NEMS

(nanoelectromechanical systems) and quantum fluids. Refrigeration by

Adiabatic Demagnetization of Cu or PrNi5 nuclei is the most common way

to achieve this temperature range [1]. Such a cooler uses a ~10 mK pre-

cooling stage provided by a dilution refrigerator. In the present

development, we plan to use a He free « dry » dilution refrigerator

similarly to previous works [2, 3] but with the goal of providing continuous

cooling below 1 mK, which hasn’t been achieved so far.

As heat switches (HS) are of major importance in the final performance of

the system, a first step will consist in characterizing existing HS and

improving their performance, in particular the thermal contacts.

In parallel, the overall system shall be designed taking into account all the thermal constraints (parasitic

loads, thermal resistances, heat capacities, etc) but also the magnetic field aspects (available space in

the dilution refrigerator, shielding, etc)

Available facilities: The student will be part of the ultra-low temperature group (UBT) of Institut Neel.

For the purpose of the development, 2 dry refrigerators will be used. The first one is a homemade dry

dilution refrigerator presently under re-assembly. The second one is a commercial dry fridge that will

be shared with sicentific experiments.

[1] Andres K and Lounasmaa O V 1982. Progress in Low Temperature Physics, vol 8, ed D F Brewer

(Amsterdam: Elsevier) chapter 4, pp 221–87

[2] G. Batey et al.; New J. Phys. 15, 113034 (2013).

[3] I. Todoshchenko et al.; Review of Scientific Instruments; 85 ; 085106 (2014)

Possible collaboration and networking: For the M2 internship, no specific collaboration is foreseen.

In the frame of a PhD, collaboration with industry and with other low temperature groups in Europe.

Possible extension as a PhD: Yes.

Required skills:

- Ability to work in autonomy

- Good competencies in low temperature physics and, more generally, in condensed

matter physics

- Good skills for experimental work

- English (fluent)

Starting date: Flexible

Contacts : Name : Fefferman Andrew / Triqueneaux Sébastien Institut Néel - CNRS

Phone : +33 (0)4 76 88 90 92 e-mail : [email protected]

Phone : +33 (0)4 76 88 12 02 e-mail : [email protected]

More information : http://neel.cnrs.fr



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Spectroscopic study of free, only optically trapped nanorods

General Scope : Over the last years optical tweezers became a standard tool for non-invasive nano-

manipulation in biology, chemistry, and soft-mater physics. In this context we have developed an

original approach based on the use of optical fiber nano-tips and we demonstrated stable and

reproducible optical trapping of micro- and nanoparticles. One major application of optical tweezers consists in the

characterization of the optical properties of trapped

particles, including emission spectra and optical lifetime

measurements. The possibility to study free, only optically

trapped particles, allows us to reduce significantly any

environmental influence. Moreover our specific tweezers

geometry allows to capture the particle emission in three

orthogonal directions, with sub-micron spatial resolution in

one direction.

Research topic and facilities available: The overall scope

of the internship is to implement to the existing optical

fiber tip tweezers and to run spectroscopic facilities adapted for europium-doped NaYF4 nanorods. The

main features are parallel recording of spectroscopic signals captured by at least two of the three possible

routes of our set-up (trapping fiber, auxiliary fiber for spatial scanning, and microscope objective) and

fluorescence lifetime measurements. Both measurements will be run as a function of the position on the

nanorod. The available equipment includes a spectrometer with a state of the art EM-CCD camera, an

electro-optical modulator, a high speed photodiode and a numerical oscilloscope. In this context europium-doped nanorods are of great interest for their very strong orientation dependent

emission. Moreover, the length and aspect ratio of NaYF4 nanorods can be controlled, thus allowing us

to study rods with lengths from 600 nm to up to 2 µm. Recent results have revealed the paramount

influence of the rod length on the trapping behavior, with short rods trapped within two fiber tips and

long rods with only one fiber tip. The obtained results will be interpreted in close collaboration with the

colleagues elaborating the particles. If available they will be compared to similar results obtained by

confocal microscopy.

Possible collaboration and networking: The internship is part of the ongoing SpecTra project which

is founded by the French National Research Agency (ANR). The work will be done in collaboration

with the LPMC at Ecole Polytechnique for the nanorod elaboration and ICB at Dijon for theoretical

considerations.

Possible extension as a PhD: YES

Required skills: Student should have skills in experimental work and have a background in optics and

nanosciences. She/ he will get insight in the very busy domains of optical trapping and nano-physics. Starting date: free as a function of academic program

Contact: Jochen Fick, Institut Néel - CNRS

Phone: 04 76 88 10 86 e-mail: [email protected]

Nanorod trapping in our optical fiber

nano-tweezers using two fiber tips. The

third tip is used for the particle emission

capture.



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Coupling a single quantum dot to a mechanical oscillator

General Scope:

Owing to the recent progress in nanotechnology and in ultra-sensitive motion detection methods,

it becomes now possible to associate quantum systems such as superconducting qubits, spins, atoms or

quantum dots to mechanical oscillators. These hybrid systems can be used as ultra-sensitive motion

sensors to detect magnetic or electric field with unprecedented sensitivity. They can also offer the

perspective of storing quantum information on mechanical degrees of freedom.

A few years ago, we have realized

such an hybrid system made of a vibrating

wire and a semi-conducting quantum

dot1,2,3. The very large coupling between

these two subsystems relies on

mechanical strain (cf figure). The

quantum dot undergoes periodic strain as

the wire oscillates along its fundamental

flexural mode at around 500 kHz. The

alternatively tensile and compressive

strain periodically alters the quantum dot

energy levels and therefore the spectral

position of the photoluminescence lines.

Research topic and facilities available: We want to explore the reverse aspect of this coupling by investigating how the resonant optical

excitation of a single quantum dot affects the motion of the oscillator. The first possibility is to set the

wire in motion by exciting a quantum dot, realizing a nano-engine powered by a single quantum dot4.

This realization will raise issues in the field of quantum thermodynamics, where we have a

strong local theoretical support with the group of A. Auffèves. A second possibility is to measure

non-destructively the quantum dot population via a mechanical read out.

The experiment consists in a microphotoluminescence set-up operating at a temperature of

T=4K, and equipped with nanomechanical detection schemes.

References 1 I. Yeo, et al, Nature Nanotechnology 9, 106 (2014) 2 P.L. de Assis et al, Phys. Rev. Lett. 118, 117401 (2017) 3 D. Tumanov et al, Appl. Phys. Lett. 112, 123102 (2018). 4A. Auffèves et M. Richard, Phys. Rev. A 90, 023818 (2014),

Possible collaboration and networking : J. Claudon, J.M. Gérard, CEA/INAC Grenoble;

A. Auffèves, O. Arcizet, Institut Néel; P.L. de Assis, Campinas, Brazil.

Possible extension to a PhD: Yes

Required skills: This experimental internship will deal with nano optics, nanomechanics and semi-

conductor physics.

Starting date: between January and April 2019

Contact:

Name: Jean-Philippe Poizat



More information: http://neel.cnrs.fr/spip.php?rubrique47

http://dx.doi.org/10.1038/nnano.2013.274

https://doi.org/10.1103/PhysRevLett.118.117401

https://doi.org/10.1063/1.5025313

http://dx.doi.org/10.1103/PhysRevA.90.023818


http://neel.cnrs.fr/spip.php?rubrique47



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Studying electrical properties of nanowires by in-situ electron holography

General scope:

Nano-objects such as nanowires (NW) and nanotubes are promising candidates for many device

applications ranging from electronics and optoelectronics to energy conversion and spintronics. To

allow successful device integration, detailed knowledge and ultimately control of the electrical

properties of these nano materials at nm length scales are fundamental.

Research topic and available facilities: The aim of this internship is to contribute to the study of semiconducting nanowires regarding their

electrical properties. Off-axis electron holography is a powerful interferometric method taking place in

a transmission electron microscope which allows retrieving the phase shift of the transmitted electron

wave. As the phase shift is sensitive to the electrostatic potential, the electrical properties of the sample

can be measured at the nanoscale.

We aim to apply this technique to a nanowire containing a p-n junction in combination with in-situ

biasing to obtain a quantitative measurement of the electric potential in the nanowire and to probe the

electrically active doping concentration. The student will work in a larger project were p-n junctions

will be studied in different semiconducting nanowire materials, being germanium, gallium nitride and

indium phosphide. The student will focus on one of these material systems that will be defined at the

start of the internship. The student will have access to a state of the art cleanroom and transmission

electron microscope. We have developed sample fabrication based on nitride membranes to make

suspended and contacted nanowires compatible with electron holography that the student will use.

The student’s work will involve:

- (Assisting with) sample preparation

by cleanroom fabrication techniques

including optical and electron beam

lithography.

- Preliminary electrical experiments to

check the sample quality.

- Performing the electrical part of in-

situ TEM experiments (TEM will be

performed by the supervisors),

treatment, correlation and

interpretation of electrical and

imaging results.

From top to bottom: schematics of the nanowire doping,

hologram, phase image showing doping contrast.

Possible collaboration and networking: The internship will be in collaboration with CEMES Toulouse

(Christophe Gatel). Potential collaborations with Vienna University of Technology and Technical

University of Eindhoven.

Possible extension as a PhD: yes (funded European project)

Required skills:

Interest in solid-state physics, electrical properties and characterization techniques and transmission

electron microscopy.

Starting date: Jan/Feb 2019 or for a longer internship asap.

Contact: den Hertog Martien

Institut Néel - CNRS : tél: 0476881045 mail: [email protected]

More information at: http://neel.cnrs.fr




23

Investigating Multiferroïcity in Doubly Ordered Perovskites

Keywords: Multiferroic materials, Structure, Magnetism

Context: We study a new class of multi-functional magnets called multiferroïcs,

where magnetism and ferroelectricity are strongly coupled together. For

example, electric polarization may be switched by applied magnetic

fields, and vice-versa. These types of materials, currently at the cutting-

edge of condensed matter research, are likely to form key components in

the development of future technology, for example, in memories and

logic devices [1]. Recently we have investigated a new family of doubly

ordered perovskites with the general formula NaLnTWO6 (Ln:

lanthanide and T: magnetic transition metal) and have found that these

materials were multiferroic by the virtue of a new mechanism, the so-

called “Hybrid Improper Ferroelectricity” [2,3].

Fig. 1 : Magnetic structure of the NaYCoWO6 [4]

Objective and available means:

A proper understanding of the interplay between the various physical

properties of these types of materials relies heavily on the knowledge of

the detailed crystal and magnetic structures. The aim of this Master

internship will be to synthesize new compounds with the doubly ordered

perovskites structure and study their electrical, magnetic and structural

properties. The structural investigation will be carried out using x-ray

diffraction at the laboratory as well as at the nearby large facilities when

needed. (European Synchrotron Radiation Facility and Institut Laüe

Langevin high flux neutron reactor). An extended set of physical,

magnetic and electrical measurement facilities (see for instance fig. 1 and

2) is available at Institut Néel and will be used to characterize the

samples.

Fig. 2: Electric polarization

developed under magnetic

field in NaYCoWO6 [4]

[1] S-W Cheong, M. Mostovoy, Nat. Mater., 6, 2007, 13. [2] P. Zuo, PhD thesis, 2017. [3] P. Zuo, C.V. Colin, H. Klein, P.

Bordet, E. Elkaim, E. Suard and C. Darie, Inorg. Chem. 2017, 56, 8478−8489 [4] P. Zuo, C.V. Colin, H. Klein, in

preparation.

Possible collaboration and networking: The student will be working within the Materials, Radiation and Structure (MRS) team of the Néel

Institute. He/she will collaborate closely with several researchers of the MRS team (experienced

chemists, crystallographers and physicists) and work with the technical staff of the laboratory (for

Physical Characterizations, X-Ray and eventually neutron diffraction).

This Master internship could be extended into a PhD within the same research subject if a

funding source for a PhD thesis is obtained (research project grant or PhD contract awarded by the

Physics Graduate School of Grenoble).

Background and expected skills: The candidate must have a background in condensed matter physics, with good basis in materials

Science and interest for exploratory experimental physics.

Possible period for the beginning of the internship: February 2019

Contact : COLIN Claire ([email protected]) Institut Néel - CNRS : tel : 04 76 88 74 14, See

also: http://neel.cnrs.fr/spip.php?rubrique63




24

Flying qubits using ultrashort single-electron charge pulses

General Scope: Coherent manipulation of single electrons in solid-state devices is attractive for

quantum information purposes because they have a high potential for scalability. Depending on the

system used, the charge or the spin may code binary qubit information. A particular appealing idea is to

use a single flying electron itself as the conveyor of quantum information. Such electronic flying qubits

allow performing quantum operations on qubits while they are being coherently transferred. Information

processing typically takes place in the nodes of the quantum network on locally controlled qubits, but

quantum networking would require flying qubits to exchange information from one location to another.

It is therefore of prime interest to develop ways of transferring information from one node to the other.

The availability of flying qubits would enable the possibility to develop new non-local architectures for

quantum computing with possibly cheaper hardware overhead than e.g. surface codes.

Research topic: The aim of the proposed M2 internship is to develop a flying qubit architecture using

ultra-short single-electron charge pulses. In order to generate such ultra-short electron wave packets,

we will leverage on the progress made on THz photon production and use photon to electron conversion

devices to engineer THz electronic charge pulses that can be used in quantum nanoelectronics.

Fig.1: A flying electron generated above the Fermi Sea and propagating in an electron waveguide.

References:

Hermelin et al., Nature 477, 435 (2011); Bertrand et al, Nature Nanotech. 11 672 (2016)

Dubois et al., Nature 502, 659 (2013); Roussely et al. Nature Com. 9, 2811 (2018)

Possible collaboration and networking: This project is realized in close collaboration with the

nanoelectronics group in Saclay (C. Glattli), the THz laboratory of the Université de Savoie Mont-Blanc

(J.F. Roux & J.L. Coutaz), the theory group of CEA Grenoble (X. Waintal) as well as the Quantum

Metrology group (AIST), Tsukuba, Japan (S. Takada) PhD fellowship available

Required skills:

The candidate should have a good background in quantum mechanics and solid-state physics.

Starting date: anytime

Contact:

BAUERLE Christopher

Institut Néel – CNRS, Grenoble


web: http://neel.cnrs.fr



25

Growth and redox reaction at the transition metal monoxide/metal

interface

General Scope:

The building of new interfaces between oxides is of mandatory importance for the search of magnetic

and electronic properties at the nanoscale. For a decade, an intense research activity has focused on two

dimensional electron gases forming at such interfaces [Ohtomo, A. & Hwang, H. Y., Nature 427, 423-

426 (2004)]. These electronic states present a wide range of interesting properties including a

modulation of the conductivity by applying a gate voltage, superconductivity, magnetoresistance and

spin polarization. The elaboration of these interfaces requires a layer-by-layer tuning of their structure.

More recently it has been shown that 2D electron systems can be generated more easily, simply by

depositing aluminum on the surface of oxides like SrTiO3 TiO2, etc. [T. C. Rödel et al., Adv. Mater.

28, 1976 (2016)]. In this case Al gives rise to a redox reaction, resulting in an amorphous alumina layer

and oxygen vacancies at the interface acting as an electron doping (see Fig.). This phenomenon seems

to be quite general providing that a metal with low electronegativity is deposited. Our aim is to grow

and characterize interfaces with a well-defined structure (unlike amorphous alumina) by depositing

reactive metals like e.g. magnesium on simple and well defined monoxides surfaces such as CoO(100)

or NiO(100).

Research topic and facilities available: During the internship, samples will be grown by molecular beam epitaxy (MBE) and characterized by

combining low energy electron diffraction (LEED), Auger spectrometry (AES) and scanning tunneling

microscopy (STM). High quality CoO(100) or NiO(100) films will be obtained by reactive metal

deposition in molecular oxygen atmosphere. Mg will be deposited on top in ultra-high-vacuum. The

structure of the interfaces showing the desired epitaxial relationship will be determined using

synchrotron radiation x-ray diffraction (as a function of the beam time allocation). This is an essential

preliminary step to the measurement of their electronic properties. In situ resonant x-ray diffraction will

be also employed, when adapted, to gather the onset of induced electronic state measuring the diffracted

signal change at the transition metal adsorption edge. Such a technique is sensitive to the electronic

properties of sharp interfaces.

Possible extension as a PhD: Yes

Required skills: Solid-State Physics, Nanoscience

Starting date: March 2019

Contacts:Maurizio De Santis,, Phone: 04 76 88 74 13, e-mail: [email protected]

Yves Joly, Phone: 04 76 88 74 12; Aude Bailly, Phone: 04 76 88 74 13

Institut Néel - CNRS (Surfaces – Interfaces - Nanostructures Team)


Schematics of the

mechanism of formation of

a highly doped 2DES in

ZnO (from Rödel et al.,

Phys. Rev. Mat. 2,

051601(R) (2018)




26

Properties of magnetic tunnel junctions with a spin-filtering layer

General Scope:

Research topic and facilities available: We have recently grown Fe3O4/MgO/CoFe2O4 multilayers on Ag(100) using reactive molecular beam

epitaxy (MBE). In this system the magnetite layer constitutes the magnetic electrode, while the cobalt

ferrite acts as a spin-filter. The properties of this system depend on the epitaxial relationship with the

Ag substrate. It is known that a compressive strain induce an in plane magnetization in cobalt ferrite. In

our system, this effect need to be investigated in details and systematically as function of the film

thickness.

Fig. 2 LEED pattern recorded at different stages of Fe3O4/MgO/CoFe2O4 /Ag(100) growth, showing a good

epitaxy with the substrate and between each layer (a: Ag; b,c,d: Fe3O4, MgO, and CoFe2O4 surfaces ).

During the internship we will growth CoFe2O4 layers of different thickness and we will measure their

magnetic properties by SQUID magnetometry. Once optimized the properties of the cobalt ferrite

barrier, a complete Fe3O4/MgO/CoFe2O4 /Ag(100) device will be elaborated and its magnetoresistence

will be measured by conductive AFM.

Possible collaboration and networking: Technological groups at Néel Institut.


Required skills: A good background in condensed matter physics


Contacts: Maurizio De Santis, Phone:04 76 88 74 13, e-mail: [email protected];

Farid Fettar, Phone:04 76 88 74 11 42; Jean-Marc Tonnerres, 04 76 88 74 15.

SIN Team (Surfaces – Interfaces - Nanostructures Team) Institut Néel - CNRS


Spin based electronics take advantage of both the

electron charge and spin in solid-state systems. A

crucial component in applications is the magnetic

tunnel junction (MTJ), where two magnetic layers

sandwich a non-magnetic one. Its conductance

depend on the relative spin orientation of the two

electrodes. An alternative way for generating spin-

polarized currents is based on MTJ with magnetic

barrier materials, which results in spin dependent

tunneling probabilities (Fig. 1). Efficient spin-

filtering has been demonstrated for ferromagnetic

insulators such as EuS and EuO, which show low

transition temperatures. Spinel ferrites like CoFe2O4

are promising candidates for room-temperature spin

filtering.

Fig. 1 Schema of spin filtering (J S

Moodera et al.,J. Phys.: Condens. Matter

19 (2007) 165202



27

STM/STS studies of two-dimensional semiconductors doped with magnetic

atoms.

General Scope:

In the monolayer limit, two dimensional (2D) transition metal dichalcogenides (TMDC: 1H-MX2, with

M=Mo, W and X=S, Se) are semiconductors with a direct electronic gap and degenerate valleys (and

opposite spins) at the K/-K corners of the Brillouin zone. This peculiar electronic structure opens

exciting possibilities for information processing that exploit the quantum degree of freedom known as

the valley index. This is « valleytronics ». Indeed, K/-K valleys can be selectively addressed e.g. by

using circularly polarized light. However, for practical uses of these materials in valleytronics, a means

to lift permanently the valley degeneracy is required. One promising route to reach this objective is to

incorporate substitutional magnetic atoms in the TMDC materials during growth.

Research topic and facilities available: The aim of the internship is to investigate by means of scanning tunneling microscopy and

spectroscopy (STM/STS) at low temperature in ultra-high vacuum the atomic and electronic structure

of magnetically doped TMDC layers. The main point will be to analyse the distribution of the

substitutional (magnetic) atoms in the material and to determine whether they induce localized states

and doping. As a probe with “atomic” scale resolution, STM is well suited for such studies. The data

will be compared to ab-initio calculations performed in the Néel Institute. The experimental setup is

available and we have already performed the characterization of the undoped phases (see figure 1).

Figure 1 : a) 60x60 nm² STM image of a monolayer MoSe2 flake on graphene. b) STS spectrum showing

the band edges of monolayer MoSe2 in a defect-free area.

Possible collaboration and networking: This program is developed in collaboration with groups in INAC/Spintec and Institut Néel, which

prepares the samples by molecular beam epitaxy. It is part of an ANR project funded for the period

2019-2022. It inserts in a larger program that aims at developing activity on TMDC in Grenoble


Required skills: Good background in solid state physics (electronic structure of solids).

Starting date: 2019

Contact:

Name: Jean-Yves Veuillen






28

Functionalization of suspended thermoelectric nano-generators

General Scope:

With the emergence of Industry 4.0, the possibility for wireless sensors to harvest small

quantities of energy (100 µW – 1 mW) in their environment for becoming autonomous is

attracting a lot of attention from both the scientific community and the economic world. Among

different sources of energy, thermal energy presents the

advantage to be available almost everywhere but in

small quantities. To adress the challenge of thermal

energy harvesting, we have developed a planar

thermoelectric generator. It is made of suspended

membranes which are very sensitive to small

intermittent temperature gradient thank to their very low

mass.

Research topic and facilities available:

The expertise developed at the Institut Néel in the

development of suspended sensors dedicated to thermal

measurements at very low temperatures has been used

to design a suspended thermoelectric nano-generator.

The duplication of this thermoelectric nano-module

thanks to standard clean room techniques enabled us to

power sensors and to transmit the information using low

power wireleess protocol (see figure 1).

The main goal of the internship would be to use the

suspended membranes as a support for the deposition

of an active thin film giving to the device another

features. It could magnetic materials for sensing

magnetic fields variation and/or phase change material

(PCM) for stocking energy and rereleasing it when the

temperature of the device is going down a given value.

Possible collaboration and networking:

A start-up exploiting these patents is going to be created. Today, three companies (SNCF, Air

Liquide and Schneider Electric) are working with us for applications of the energy harvesting

system. The team is involved in French and European network of thermal engineering.

Possible extension as a PhD: The internship could be followed by a PhD

Required skills: A Master level in applied physics is required.

Starting date: Spring 2019

Contact:

Name: Dimitri Tainoff




Figure 1 : SEM image of an individual micro-thermogenerator. The membrane is suspended and a functional material having phase transition will be deposited at its center to reach new properties. The micro-generator are then duplicated and integrated into small prototypes built in the frame of collaboration with industrial partners.



29

High temperature superconducting oxychlorides: a light element model for

cuprates

General Scope:

Cuprates were discovered in 1986 to show superconductivity at the highest temperature at ambient

pressure, a record they still detain (see figure), but their phenomenology apparently cannot be grabbed

by present theory, so that they are considered among the main unsolved problems in physics today. In

this context, the discovery of the Na and vacancy doped Ca2CuO2Cl2 oxychloride is very promising

indeed to bridge the gap between theory and experiment since it: lacks high Z atoms; has a simplest

crystalline structure for cuprates, stable at all doping and temperatures; and has a strong 2D character

due to the replacement of apical oxygen with chlorine. Therefore, advanced calculations that incorporate

correlation effects, such as quantum Monte Carlo are easier, but relatively little is known about

Ca2CuO2Cl2 from an experimental point of view. We are now filling this gap by a comprehensive

experimental study covering the whole phase diagram, in particular of the magnon and phonon

dispersion, using advanced approaches based on synchrotron radiations.

Figure 1: Cuprates allows exploiting magnetic

levitation above the liquid Nitrogen temperature,

as shown in the picture (Mai-Linh Doan wikimedia

commons, © Creative commons).

Research topic and facilities available: Most of experiment will be planned at synchrotron facilities in europe and around the world, mainly at

ESRF (Grenoble) and SOLEIL (Paris region), but also at NSLS-II (Brookhaven, US), Spring-8 (Japan)

as well as other facilities depending on available techniques, in order to unveil their electronic properties

at a microscopic level.

Preparation of these experiments will require special care, as the materials are sensitive to air, so that a

special glove box is under installation at the Néel institute, and we will use its facility to growth (large

volume press), crystalline (x-ray diffraction) and superconducting (magnetometry) characterisation.

Possible collaboration and networking: Interpretation of the results will be made with group performing ab-initio electronic structure calculation

including correlation effects in Paris (Ecole Polytechnique) and USA (University of Illinois). Sample

synthesis will be made in collaboration with the group of Prof. I. Yamada (Univ. of Osaka, Japan). Part

of the synchrotron spectroscopy studies will be performed in collaboration with M. Dean (Brookhaven

National Laboratory).

Possible extension as a PhD: Yes, this project is part of a PhD program, of which this Master Internship could be a first approach.

Required skills:

A good background in electronic properties of material, with the will to have a global approach, from

material synthesis and characterisation to advanced spectroscopic properties. Team work will be an

essential part of the project success.

Starting date: Winter 2019

Contact:

Name: D'ASTUTO Matteo


Phone: (+33)(0)4 76 88 12 84 e-mail: [email protected]





30

Epitaxial growth of hybrid nanowires for topological quantum computing

General Scope:

One interesting and promising proposal for quantum computation relies on the so called topological

protected quantum bits. Realizing such quantum bits depends on the ability to make materials that can

host Majorana bound states. In 2012, signatures of such states were reported in one-dimensional

semiconductors with high spin-orbit coupling, coupled to a superconductor. Since then, nanostructured

hybrid materials based on superconductor/semiconductor interfaces have received increased attention.

Yet, controlled formation of topological protected states can only be realized if the

superconductor/semiconductor interface is of high quality. Creating those interfaces in an epitaxial

fashion would have many advantages, among them better transparency, controlled interface chemistry,

higher current injection and lower disorder.

Combining crystalline metals and semiconductors is challenging because of the fundamental different

properties of both families of materials. In-situ epitaxial growth of InAs/Al and InAs/Nb core-shell

nanowires were recently developed. The InAs/Al nanowire devices revealed a superconducting hard

gap, demonstrating the high potential of in-situ shell epitaxy. Such structures are currently studied at

Microsoft Station Q to build a topological quantum computer. In our project, we propose to develop

novel hybrid interfaces using vanadium and tantalum grown epitaxially on InAs. These novel

combinations of materials have strong potential not only to understand crystal growth but also to reach

the Majorana regime and perform further topological experiments thanks to the higher critical field of

V and Ta in comparison with Al.

Research topic and facilities available: In this project, the student will carry out the growth of inclined hybrid nanowires in a III-V molecular

beam epitaxy reactor. She/he will focus on InAs/V and InAs/Ta core/shell nanowire fabricated using

templates developed in the cleanroom. The student will perform the characterization of the samples by

SEM and EDX. Together with partner labs, she/he will participate in low temperature measurement

campaigns using a dilution fridge to probe the superconductivity induced in the InAs nanowires.

Moreover, high-end structural characterizations (TEM, XRD) will be performed on the hybrid

nanowires to unravel the growth mechanisms at the superconductor/semiconductor interface.

Collaboration and networking: University of Pittsburgh (S. Frolov)

University of California in Santa Barbara

(C. Palmstrom)

CEA-INAC (J. Meyer, M. Houzet, F. Lefloch)

Possible extension as a PhD: Yes (funding from ANR PIRE HYBRID)

Required skills:

Motivated experimentalist

Programming (Python)

Starting date: march 2019

Contact:

Name: Moïra Hocevar

Institut Néel - CNRS Phone: 04 78 38 35 13


More information: https://pirehybrid.org

(a) (b)

(c)

(a) InAs nanowires will be grown by the VLS mechanism using

gold catalysts. Then a shell will be fabricated by switching the

growth mode to 2D growth. (b) SEM image of a sample of

inclined InAs nanowires. (c) SEM image of a core-shell nanowire

device.



31

Quantum circuits and the Superconductor-Insulator transition

General Scope: During the last decade, it has been demonstrated that superconducting circuits

embedding Josephson junctions behave as quantum bits or qubits. These circuits appear as artificial

atoms whose properties are defined by their electronic characteristics (capacitance, inductance and

tunnel barrier). As of today, they are considered as one of the most promising platform to perform

quantum computation.

On the other hand, understanding the details of the Superconductor-Inductor phase transition remains

one the most challenging problem in condensed matter physics since it merges various ingredients such

as interactions, mesoscopic superconductivity or disorder.

This project aims at using the tools developed for superconducting qubits to gain new insights on the

Superconductor-Insulator transition and more specifically on one of the most intriguing and promising

disordered superconductor: Indium Oxyde (InOx) [1]. It builds on the expertise of two teams at the Néel

Institute: the quantum coherence team (supervisor: Nicolas Roch) and the quantum nanoelectronics and

spectroscopy team (supervisor: Benjamin Sacépé).

During a very recent effort to bridge these two fields of research, we already obtained very exciting

preliminary results using a very long microwave InOx resonator (see figure and [2]).

[1] Low-temperature anomaly in disordered superconductors near Bc2 as a vortex-glass property,

B. Sacépé et al. arxiv:1609.07105, Nature Physics (2018) in press

[2] Probing light-matter interaction in the manybody regime of superconducting quantum circuits, Javier

Puertas-Martinez, PhD Thesis, Grenoble Alpes University (2018).

Research topic and facilities available: Both teams have a strong experience in nanofabrication and

cryogenic equipment. The quantum coherence team specializes in the coherent control and manipulation

of superconducting qubits while the quantum nanoelectronics and spectroscopy team is internationally

renowned for its expertise on InOx. The student will use state-of-the-art setups combining very low

temperatures (around 10 mK), quantum-limited microwave detection chains and high-magnetic fields

(up to 15 T) to study. The devices are fabricated in the clean room of the Neel Institute (Nanofab). If the

candidate is interested in learning these fabrication techniques, she/he can be associated to this part of

the project as well.

This internship can be pursued toward a PhD

Required skills: Master 2 or Engineering degree. We are seeking motivated students who want to take

part to a state of the art experiment and put some efforts in the theoretical understanding of the

Superconductor Insulator transition.


Contacts: ROCH Nicolas ([email protected] ) website : http://perso.neel.cnrs.fr/nicolas.roch

SACEPE Benjamin ([email protected] ) website: http://sacepe-quest.neel.cnrs.fr/

Measured InOx resonator. (a) Circuit

diagram of the sample. It consists of a

transmission line of impedance Z and

propagation constant k coupled via

capacitances Cc to input and output 50 Ω

ports. (b) Optical image of the sample

showing one of the coupling capacitors

and one 50 Ω pad. The pads are made of

gold. The substrate is silicon. (c) SEM

image of the InOx wire. It corresponds to

the blue square in (b).


http://perso.neel.cnrs.fr/nicolas.roch


http://sacepe-quest.neel.cnrs.fr/



32

Wannier Resonances and Two-Frequency Problems in Three-Terminal

Josephson Junctions

Introduction : Since the beginning of the

1960s, the Josephson effect has focused interest of

the condensed matter physics community. It lead to

major applications in the field of quantum

information and technologies. The Josephson

effect appears when two superconductors are

connected by a non-superconducting material, and

the underlying mechanism is related to the

formation of Andreev bound states. These Andreev

doublets produced by the proximity effect appear

in the gap, and they are sensitive to the

superconducting phase. The Andreev bound states

can be seen as two-level systems, and they are due

microscopically to the formation of pairs of

entangled electrons in the normal conductor. Many

properties of the Josephson effect, such as the

value of the current, depend on the energy-phase

relation of the Andreev bound states at zero bias

voltage. A deep analogy appears between band theory in solid state physics and Josephson junctions. For

instance, the superconducting phase between 0 and 2 π plays the role of the wave-vector in the first

Brillouin zone. On the other hand, the acceleration of the electronic wave-vector due to an electric field

(which leads to Bloch oscillations [Zener1934]) is similar to the Josephson relation for the time

evolution of the superconducting phase variable. Josephson junctions are thus expected to produce

effects similar to those of solid state physic, like spectral properties [Wannier1960] of Bloch oscillations

[Zener1934], or topology-related effects. Context : Our goal since several years has been to determine the fate of the equilibrium Andreev

bound states in the presence of bias voltage. We have developed recently [Mélin2017] numerical and

analytical calculations for three-terminal superconductor – quantum point contact – superconductor

junctions (see figure above). We have developed an analogy between the nonequilibrium dc Josephson

effect and notions from band theory. The nonequilibrium Andreev bound states look like “ladders of

Wannier-Stark resonances” in semi-conducting superlattices [Wannier1960], which were observed by

optical spectroscopy in the end of the 1980s [Mendez1988]. We have discovered two new effects on the basis of numerical calculations for a time-periodic

Hamiltonian: correlations between Cooper pairs [Freyn2011] which were already demonstrated

experimentally [Cohen2017]. Second, Wannier-Stark ladders [Mélin2017] are the subject of an on-

going experimental work in the group of Romain Danneau in Karlsruhe. Methods more general than

those relying on time periodicity will have to be developed in order to address two-frequency problem,

for instance to sweep the Brillouin zone associated to superconducting phases in order to calculate a

Chern number [Riwar2016]. The PhD thesis project aims at exploring such problems with two

independent frequencies, which can be in a commensurate or incommensurate ratio. Work program for the internship : A simpler problem will be proposed for the internship, so

that the student can become acquainted with recursive Green’s functions, in connection with an on-

going experiment in Grenoble on the role of nonequilibrium quasiparticle populations injected by the

tip of a scanning probe microscope in a two-terminal Josephson junction. Results on this problem are

expected within a short period of time.

A three-terminal Josephson junction, in which a

quantum point contact x is connected to three

superconductors.



33

Work program for the PhD thesis : The first project of the PhD thesis will be to justify the Markovian

approximation by testing it against numerically exact calculations that we master well [Mélin2017].

Once the method will have been tested, it will be proposed to couple a two or three-terminal Josephson

junction to ac voltages, in order to excite transitions between Wannier-Stark levels belonging to different

sub-bands. Two approaches will be developed: calculations based on the density matrix in the

Markovian approximation which will be compared to the rotating wave approximation. These

calculations will pave the way to NMR-type manipulations of a Floquet two-level system.

It will be also proposed to calculate the finite frequency noise spectrum, in connection with the

experiments in Romain Danneau’s group at the Karlsruhe Institute of Technology in the framework of

a Grenoble-Karlsruhe international laboratory The goal of these experiments is to provide evidence for

Floquet-Wannier-Stark ladders. Finally, as mentionned above, it will be proposed to address a two-frequency problem, allowing

for sweeping the Brillouin zone of the two relevant phase variables in the presence of two slightly

different bias voltages Va and Vb in an incommensurate ratio. This type of problem with a “slow” and a

“fast” frequency was treated with micro-local analysis in the mathematical community, and it was used

in Grenoble in order to calculate the bottom of the Hofstadter spectrum for a network of superconducting

wires (Wilkinson-Rammal approach, in connection with Pannetier’s experiments [Wang1987]). It will

be proposed to develop these calculations in close collaboration with Frédéric Faure and Alain Joye at

Institut Fourier in the mathematics department of Grenoble-Alpes University. It will also be proposed

to tackle this question in the framework of the Markovian approximation. In particular, special care will

be devoted to the fate of topology in the presence of relaxation, in connection with heat flows. Environment of the projects : This project is within a long-standing collaboration between

Régis Mélin et Benoît Douçot. Numerical calculations will be carried out on the Rouen platform

(CRIANN) through a collaboration with Jean-Guy Caputo (applied mathematics at INSA-Rouen). A

French-German ANR international project was proposed with Romain Danneau, who fabricates devices

based on bilayer graphene, and realizes finite frequency noise measurement of Josephson junctions.

Finally, a collaboration has started with Frédéric Faure and Alain Joye in the mathematics department

of the Grenoble-Alpes University, with regular meeting on a monthly basis.

Advisor : Régis Mélin, Institut Néel, Grenoble

Co-Advisor : Benoît Douçot, Laboratoire de Physique Théorique et des Hautes Energies, Paris

Possible extension as a PhD: The internship could be followed by a PhD Required skills: The candidate should be familiar with advanced quantum mechanics Starting date: Spring 2019 Contact: Régis Mélin, CNRS, Institut Néel Grenoble, Phone number: +33-4-76-88-11-88 E-mail address: [email protected]




34

Cavitation at the nanoscale

Keywords: statistical physics, porous materials, helium, low temperature, optics

General Scope:

Cavitation, i.e. the formation of a vapor bubble in a stretched liquid, is of fundamental interest. For

decades, the consensus has been that, in bulk liquid, cavitation occurs via the stochastic formation of a

bubble nucleus as described by the classical nucleation theory. We want to elucidate whether this also

holds for liquids confined at the nanoscale.

Research topic and facilities available: Cavitation takes place when liquids are in a metastable state below their saturated vapor pressure. It is

possible to reach this state through active techniques such as ultrasonic waves or intense mechanical

stirring. Alternately, natural evaporation in trees drives their sap to large negative pressures, eventually

triggering adverse cavitation. This has inspired a different route to study cavitation, namely the

‘synthetic tree’ concept: the idea is to have liquid inside a cavity connected to a vapor reservoir through

a narrow neck also filled with liquid. When pressure in the vapor reservoir is reduced, the liquid inside

the cavity is forced to large negative pressures, allowing to observe cavitation (see fig a).

Using fabrication techniques (coll. L. Cagnon), we have obtained this geometry with alumina

membranes (fig b) where cavities have nanometric sizes. They are made out of individual cylindrical

pores, where they self-assemble in hexagonal arrays (fig c, SEM top view). The cavities are defined by

changing the diameter of the pores during the growth process (fig d, SEM side view). The first results show

that conventional fluids indeed cavitate inside these samples. The task of this intership will be to

elucidate whether cavitation can also be observed with liquid helium. This preliminary step opens the

way to a thesis studying the dependence of cavitation on the cavity size.

The team

Our team (2 permanents + 1 postdoc) works at the crossroads of low temperature and statistical physics,

focusing on porous materials. We use an original approach where the fluid of interest is helium, taking

advantage of its unique properties as compared to other fluids.

Possible collaboration and networking: This work is part of the project CAVCONF supported by ANR. In this framework, the PhD student will

participate to experiments using complementary techniques and fluids at Ecole Normale Supérieure

(LPS-ENS, Paris) and Université Pierre et Marie Curie (INSP, Paris).

Possible extension as a PhD: yes Required skills: the candidate should have a background in condensed matters physics

Starting date: flexible to the trainee academic program

Contact: Panayotis Spathis / Pierre-Etienne Wolf [email protected] / [email protected] For more information:

- on the ‘artificial tree’ concept @ Cornell: http://www.stroockgroup.org/home/research

- on the fabrication process: http://neel.cnrs.fr/spip.php?article2056&lang=fr

- on the team: http://neel.cnrs.fr/spip.php?rubrique162 or better: drop by the lab!

http://www.stroockgroup.org/home/research#TOC-Synthetic-Trees---science-and-engineering-of-water-under-tension:

http://neel.cnrs.fr/spip.php?article2056&lang=fr




35

Testing the Classical Nucleation Theory

Keywords: statistical physics, porous materials, nanofabrication techniques General Scope:

Cavitation, i.e. the formation of a vapor bubble in a stretched liquid, is of fundamental interest. For

decades, the consensus has been that its occurrence is correctly described by the Classical Nucleation

Theory (CNT). However, very few experimental studies are in quantitative agreement with this theory.

Our goal is to test its accuracy through benchmark cavitation experiments. Research topic and facilities available: Cavitation takes place when liquids are in a metastable state below their saturated vapor pressure. It is

possible to reach this state through active techniques such as ultrasonic waves or intense mechanical

stirring. Alternately, natural evaporation in trees drives their sap to large negative pressures, eventually

triggering adverse cavitation (see a simplified view fig a). This has inspired a different route to study

cavitation, namely the ‘synthetic tree’ concept: the idea is to have bulk liquid connected to a vapor

reservoir through a porous structure also filled with liquid. When pressure in the vapor reservoir is

reduced, nanometric menisci develop in the porous structure, forcing the liquid to large negative

pressures for which cavitation can occur (see fig b).

The task of this internship will be to design and build the first samples using nanofabrication techniques.

Porous silicon membranes will be synthesized and then bonded on patterned glass substrates. The

behavior of fluids condensed inside these samples will then be studied to measure their equation of state

at negative pressure. Subsequently, the occurrence of cavitation will be monitored with optical

techniques and compared to the predictions of the CNT.

The team

Our team (2 permanents + 1 postdoc) works at the crossroads of low temperature and statistical physics,

focusing on porous materials. We use an original approach where the fluid of interest is helium, taking

advantage of its unique properties as compared to other fluids.

Possible collaboration and networking: This work is part of the project CAVCONF supported by ANR. In this framework, part of the fabrication

will be done at Université Pierre et Marie Curie (INSP) and some measurements at Ecole Normale

Supérieure (LPS-ENS, Paris).

Possible extension as a PhD: yes Required skills: the candidate should have a background in condensed matter physics, with a focus on

nanosciences.

Starting date: flexible to the trainee academic program

Contact: Panayotis Spathis / Pierre-Etienne Wolf [email protected] / [email protected] For more information:

- on the ‘artificial tree’ concept @ Cornell: http://www.stroockgroup.org/home/research

- a review on porous silicon : http://www.mdpi.com/1996-1944/3/2/943

- on the team: http://neel.cnrs.fr/spip.php?rubrique162 or better: drop by the lab!

http://www.stroockgroup.org/home/research#TOC-Synthetic-Trees---science-and-engineering-of-water-under-tension:

http://www.mdpi.com/1996-1944/3/2/943




36

Guided interactions with rare-earth luminescent centers for quantum

information processing

General Scope: Rare-earth ions because of their unique 4f electronic configuration form well isolated systems when

embedded in solids. They have long coherence time at low temperature making them highly promising

qubits for the development of quantum technologies. Their well-known optical transitions, historically

exploited for lasers, can be now used as a support for optical quantum memories and more generally as

a fast and versatile element of control on the qubit. High quality optical crystals containing rare-earth as

low concentration impurities can be obtained routinely. The qubit manipulation using both optical and

radio-frequency excitations is directly performed on millimeter-size bulk with a going through laser

beam and proximity electrodes RF coupling (see figure). Higher integration is desired not only to

improve the readiness level of quantum technologies but also to obtain a stronger optical and RF

coupling leading to a faster operation time.

Research topic and facilities available: In this project, we propose to investigate experimentally a new platform for rare-earth based quantum

processing by considering epitaxial semiconductors as host matrices instead of bulk oxides (see figure).

The growth and fabrication of III-V semiconductors inheriting from years of development in electronics

allow to access micro- and nano-size samples. Bulk devices can now be compacted by three orders of

magnitude allowing a stronger (optical and RF) fields confinement and a much faster qubit control as a

consequence. At the start of the project and depending on the expectation of the candidate, the internship can be

oriented toward the growth/fabrication and/or the design of the optical setup using commercial templates

as a testbed. Both aspects are very demanding in terms of technical skills with epitaxial material

engineering on one side and optical design in low temperature environment on the other side.

Possible collaboration and networking: M. Hocevar, M. Urdampilleta (Institut Néel), B. Daudin

CEA/INAC, A. Bartasyte (FEMTO-ST, Besançon) Possible extension as a PhD: Yes Required skills: Experimental including optics, materials science and engineering, nanofabrication. Starting date: between January and April 2019 Contact: Name: Thierry Chanelière Institut Néel - CNRS Phone: e-mail: [email protected]

Bulk oxides doped with rare-earth ions can be advantageously

replaced by semiconductor doped matrices to shrink the device to

micro-size scale and then benefiting from a strong optical and RF

field confinements for qubit addressing.

mailto:[email protected]?subject=Master%202%20internship



37

Theoretical study of excitations in the magneto-electric RMn2O5

compounds

General Scope: Multiferroic materials are multifunctional systems that couple multiple orders and in

particular magnetism and ferroelectricity. Their interest is double. First the possibility to control

magnetism with an electric field has many potential applications in the domains of energy saving in

microelectronics or for data storage and processing. Second, the properties of these systems raise a large

number of fundamental questions. For instance, the origin or the amplitude of the magneto-electric

coupling remains to be fully understood. The complexity arises from the numerous degrees of freedom

involved that are all intrinsically interdependent. One can cite for the static aspects the structural (atomic

organisation), magnetic (spins amplitude and orientation) and dielectric (spatial distribution of charges)

parameters, while phonons and magnons may also be coupled in excited states.

Research topic and facilities available: In this internship proposal, we propose to investigate the

properties of a particular family of magneto-electric multiferroics : the RMn2O5 (R=Rare Earth).

Studying these materials is motivated by their very strong magneto-electric coupling (a field of only 2

Tesla can reverse the polarization [1]) and by the microscopic mechanism which is at work in this case

(exchange-striction)[2,3,4].

Fig.: Polarisation reversal using a magnetic field

in TbMn2O5

[1] N. Hur et al, Nature 429, 392 (2004) [2] G. R. Blake, et al, Phys. Rev. B 71, 214402 (2005) [3] G. Yahia … M.-B. Lepetit et al, Phys. Rev. B 95,

184112 (2017) [4] G. Yahia … M.-B. Lepetit et al, Phys. Rev. B 97,

085128 (2018)

For this purpose the student will perform ab-initio calculations, learn how to map them into Fermi level

effective models and to solve the latter to compare with experimental results. She/he will thus

learn the basis of electronic and magnetic struture calculations

learn how to use the supercomputers accessible in the national/regional computation centers

learn how to extract the important information from the calculation in order to built a model. For this purpose he/she will have access not only to the lab. computer facilities but also to supercomputer

centers.

Possible collaboration and networking: The student will collaborate with the experimentalists

working on this systems, namely members of the P. Foury group from the LPS (Orsay), specialists of

neutrons scattering from the LLB (Saclay) and ILL (Grenoble) neutron facilities. The student will also

collaborate with theoreticians from ILL in particular E. Rebolini.

Possible extension as a PhD

Required skills: The student should have a good knowledge of quantum mechanics, as well as

knowledge of computers usage.

Starting date: between January and March 2019, end date not after July 31st.

Contact: Name: Marie-Bernadette Lepetit - Institut Néel - CNRS Phone: (+33) 4.76.88.12.89 e-mail: [email protected]



38

Elaboration of Ln3+-doped α-La(IO3)3 thin films

General Scope:

Iodate crystals (α-La(IO3)3) present a high dielectric

susceptibility (χ2), leading to promising applications

in piezoelectricity and non-linear optics.1 In

addition, the possibility of substituting La3+ ions by

some trivalent luminescent lanthanide ions adds up

the photoluminescence as a new functionality. In

this context, we have successfully developed Er3+-

doped α-La(IO3)3 nanocrystals (size <100 nm),

exhibiting both Second Harmonic signal and up-

conversion luminescence under a near-infrared

excitation.2 One of the biggest challenges is now to

be able to deposit these compositions as thin films

for a good integration in electronic devices.

1 K. M. Ok, P. S. Halasyamani. Inorg Chem (2005) 2 S. Regny, J. Riporto, Y. Mugnier, R. Le Dantec, I.

Gautier-Luneau, G. Dantelle, in preparation

Research topic and facilities available: Lanthanide-doped α-La(IO3)3 nanoparticles are currently synthesized by microwave-assisted

hydrothermal technique with a typical size comprised between 50 and 100 nm. They will be shaped as

thin films by different methods, in particular by Pulsed Laser Deposition (PLD). The deposition

conditions will be optimized to ensure the formation of the right phase, as well as a high crystal quality.

The nanocrystals and the obtained films will be characterized by X-ray Diffraction (powder and at

grazing angle, both available at the Institut Néel), as well as by Scanning Electron Microscopy. The

nanocrystal and film photoluminescence will be quantitatively studied in the lab using a

spectrofluorimeter. The Second Harmonic Generation (SHG) will be qualitatively studied at the Institut

Néel. More advanced SHG characterizations will be performed in collaboration with the Symme

Laboratory (Annecy).

Possible extension as a PhD: Yes if funding

Required skills:

Good skills in Materials Sciences (chemical synthesis, characterization techniques: XRD, SEM)

Good writing and oral skills

Starting date: February-March 2019

Contact: Geraldine Dantelle and Mathieu Salaün


e-mail: [email protected] and [email protected]


Fig. 1. SEM image of Er3+-doped α-La(IO3)3

nanocrystals





39

DNA Nanostructure programming

General Scope:

The bottom-up fabrication of functional materials

opens a realm of applications, in particular in the

fields of life sciences and health. One can imagine

easily to build up in parralel and in-vivo nanocage

that would open-up and deliver drugs at the proper

target. Other applications could range from

fundamental molecular computations to enzymatic

pathway control. In fact these applications have

already been demonstrated using DNA as a

framework for molecular assembly. The design of

nanostructures is essentialy based on the

thermodynamic while their assembly is for some

part kinetically controlled. We propose to use toy

systems made of an essential element of

nanostructure assembly, the Holliday junction, to

investigate thoroughly the assembly of simple

nanostructure. The possibility to tune finelly

sequences in order to control the assembly pathway will be extensively used.

Research topic and facilities available: The internship will take place in a group interested in the thermodynamic of small systems and

biophysics. Our general goal is to investigate how heat is used at the nanoscale to drive molecular events.

We base our experiments on calorimetric measurements. We will combine these measurements with UV

absorption and gel electrophoresis to measure the thermodybamic properties and perform control

experiments. AFM analysis is also essential to our work and we benefit from the AFM platform at Neel.

Possible collaboration and networking: We collaborate with researchers in Symmes (INAC-CEA Grenoble) and in the LIMMS a joint unit of

the CNRS and the University of Tokyo in Japan.

Possible extension as a PhD:

Yes for outstanding students

Required skills:

General knowledge in thermodynamic, molecular biology a good organization and meticulous

manipulation are required. The team spirit is mellow but we expect students to get involved in their

project.

Starting date: ASAP

Contact:

Name: GUILLOU Hervé


Figure 2 Various object assembled using DNA as a

construction material



40

Nano-Neuroelectronics

General Scope:

While the brain is one of the most famous systems, providing and controlling every function of the

Body, it is barely understood in health and disease. New methods and new technology are required to

interrogate neuronal cells by many means and at multi-scale in-vivo, and within model neural networks

in-vitro. In particular, to understand how neural circuits operate, we need access to activity of large

numbers of neurons at the same time, and record their activity at the single cell level and at the nanoscale

regarding the lot of information which relies at the level of synapses and ion channels.

In that race, we have shown that graphene based

nanoelectronics offers an ideal platform for recording and

culturing neural networks, thanks to its flexibility,

transparency and exceptional neural affinity (Veliev 2016).

Also, the presence of readily accessible surface charges gives

the unprecedented possibility to realize a direct coupling with

cells, such the sensitivity reached in gapless graphene FET

(G-FETs) is well beyond that of current silicon technology

and allow to sense single neural spikes (Veliev et al. 2017) as

well as nanoscale event such as ion channel currents (Veliev

et al. 2018).

Research topic and facilities available: We aim to implement novel graphene based nanosensors for both in-vitro and in-vivo recording of

neuron assemblies, and combine them with several manipulation ports (optic, microfluidic and

electrical). This unique combination would allow to interrogate neuronal systems by many means and

to investigate neuronal processes within cultured and brain neuron networks.

(Veliev 2016) Veliev, F., Briançon-Marjollet, A., Bouchiat, V., & Delacour, C. (2016). Impact of crystalline

quality on neuronal affinity of pristine graphene. Biomaterials, 86, 33-41.

(Veliev 2017) Veliev, F., Han, Z., Kalita, D., Briançon-Marjollet, A., Bouchiat, V., & Delacour, C. (2017).

Recording spikes activity in cultured hippocampal neurons using flexible or transparent graphene transistors.

Frontiers in neuroscience, 11, 466.

(Veliev 2018) Veliev, F., Cresti, A., Kalita, D., Bourrier, A., Belloir, T., Briançon-Marjollet, A., ... & Delacour,

C. (2018). Sensing ion channel in neuron networks with graphene field effect transistors. 2D Materials.

Possible collaboration and networking: Such interdisciplinary project relies on strong collaborations

with numerous Physicists (theorists, material sciences, nanoelectronics, signal processing…),

Neurobiologists and Chemist at Néel and outside the lab (EPFL, IBS, IMEP, CERMAV…), as well as

‘HighTech’ plateforms for materials, nano/micro-fabrication in clean room, highly resolved microscopy

and biotechnological platform (microfluidic, cells culture, microscopy, electrophysiological setup) that

are gathered at the Néel Institut.

Possible extension as a PhD: oui

Appreciated skills condensed matter physic, nanoelectronics, materials sciences, and

electrophysiology


Contact:

Name: Delacour Cécile

e-mail:[email protected]





41

Ultrasensitive force measurements at the Quantum/Classical interface

General Scope: Optomechanical systems, which couples a light field

to a nanomechanical oscillator, have demonstrated outstanding

sensitivities for force measurements. Using a Silicon Carbide

nanowire coupled to a focused laser beam we already demonstrated

sensitivities in the atto-Newton (10-18 N) range [1]. Moreover the

vibrations of these wires consist in nearly degenerated and

orthogonal modes which allows for vectorial sensing capabilities

[1]. These amazing features, which have been employed to

investigate their interaction to a single spin qubit [2], will be applied

to design a new type of Magnetic Force Microscope (MFM) with a

sensitivity increased by six orders of magnitudes compared to

standard AFM/MFM probes and the ability to map the local

magnetization vector. These capabilities will be crucial to prove the

existence and reveal the fine structure of new exciting magnetic

states at room temperature. Among those, the stable chiral structure

of magnetic skyrmions [3] is very promising for future spintronics

applications and will be the focus of this project.

Research topic and facilities available: The goal of this project is to

detect, image and study the physics of magnetic skyrmions in thin

ferromagnetic films of Platinum/Cobalt. The first task will be to set up a nanowire based

MFM under vacuum, for which we have all the essential pieces and adapt and optimize new

signal processing protocols to accelerate the acquisition time. This task will be followed by

the fonctionalisation of nanowires with ferromagnetic nanoparticles. After preliminary

charcterisation of the instrument on calibrated nanostructures, measurements will be

performed on individual magnetic skyrmions.

[1] L. Mercier de Lépinay et al., Nature Nano 12, 156-162 (2016)

[2] B.Pigeau et al, Nature Comm. 6, 8603 (2015)

[3] A. Fert et al., Nature Nano. 8, 152 (2013).

Possible collaboration and networking: The Micro and Nanomagnetism group (Néel Institute)

will provide the magnetic nanoparticles as well as the thin films and magnetic dots hosting

skyrmions.

Possible extension as a PhD: The internship can move on a PhD.

Required skills: The candidate must have good experimental skills and a good knowledge in

optics. Prior experiment in magnetism is welcome. Starting date: In 2019

Contacts:

Benjamin Pigeau, Institut Néel - CNRS : [email protected]

Olivier Arcizet, Institut Néel - CNRS : [email protected]





42

Turbulence Quantique & Vortex

Cadre général :

En dessous de 2,17 K, l’hélium liquide acquiert des propriétés

quantiques spectaculaires : écoulement sans viscosité, quantification des

mouvements tourbillonnaires... On s’attend donc à ce que sa turbulence,

appelée « Turbulence Quantique », diffère de la turbulence « classique ».

Etonnament, plusieurs études suggèrent que la seule différence entre ces

deux turbulences se concentre aux petites échelles. En particulier, en

l’absence d’un mécanisme de dissipation efficace, une accumulation

désordonnée de tourbillons de diamètre atomique (les vortex quantiques)

est prédite, mais cet effet n’a jamais été mesuré directement.

L’objectif d’un prochain Doctorat est de détecter cette éventuelle accumulation grâce à une sonde à haute

résolution, puis de modéliser ce phénomène. Outre une meilleure compréhension de la turbulence

quantique, cette étude fournira un étalon très contraignant pour des modèles numériques développés

conjointement par nos collaborateurs.

Sujet, moyens disponibles :

Une nouvelle génération de sondes micro-fabriquées de

vortex quantiques vient d’être mise au point. Ces « pinces

à second son » d’une résolution record reposent sur

l’atténuation d’ondes thermiques en présence de vortex

quantiques (cf figure). Elles seront exploitées dans nos

souffleries superfluides.

Le sujet du stage de M2 se focalisera sur un unique aspect

de ce sujet de thèse (instrumentation / mesure en soufflerie

superfluide), ou portera sur un sujet connexe

d’hydrodynamique physique cryogénique (à discuter).

Interactions et collaborations éventuelles : Cette étude s’inscrit dans le cadre d’une collaboration inter-laboratoires visant à améliorer

significativement la capacité de simulation des écoulements quantiques (Centrale Lyon/CNRS/ENS

/Univ. Grenoble-Alpes/Univ. Rouen). Des échanges réguliers auront lieu dans ce cadre.

Ce stage pourra se poursuivre par une thèse : Oui, le financement est acquis (ANR QUTE-HPC).

Formation / Compétences développées : Hydrodynamique & Turbulence quantique, Physique des

basses températures, Nanotechnologie & micro-fabrication, Traitement du signal, Instrumentation

Période envisagée pour le début du stage : indifférente

Contact : Philippe Roche, Institut Néel – CNRS/ UGA, [email protected] http://hydro.cnrs.me

Pour candidater : merci d’envoyer CV + liste des intitulés des cours de Master (M1+M2).

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Modes de résonances d’une micro-cavité à 2nd

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présence (rouge) ou quasi-absence (bleu) de

vortex quantiques

Tourbillons superfluides

(simulations Baggaley et al.)


http://hydro.cnrs.me/



43

Superconducting Higgs mode in Monolayer systems under extreme

conditions

General Scope:

When a spontaneous breaking of a continuous symmetry takes place, for instance when crossing the normal

to superconducting transition, collective excitations of the order parameter emerge:

They are the phase modes and the massive amplitude Higgs mode, as illustrated Fig.1.

While the quest for the Higgs boson in particle physics has reached its goal and its prediction has been

rewarded with the Nobel Prize, there is growing interest in the search for analogous excitation in quantum

many body systems, notably in superconductors. Indeed, even if theoretically always here in any

superconductors and even if presented as a textbook excitation, this ‘dark’ mode (like the Higgs boson in

particle physics) remains very elusive. In principle, it does not couple to any external probe. Our purpose is

to identify and search for this Higgs mode in purely 2D monolayer systems.


The compounds where a superconducting Higgs mode has been claimed to be present are the ones where

superconductivity coexists with another type of electronic order, such as charge density wave. In these systems,

like in NbSe2 (see Fig. 2), the amplitude oscillations of the CDW order parameter (CDW mode) can be detected

by Raman spectroscopy. When the system becomes superconductor, a new Raman peak emerges. It has been

attributed to the Higgs mode. Still, such Higgs mode has not been identified in purely 2D monolayer systems,

where confinement in the plane may have strong impact on its property. The student will explore mono/bilayers

systems by Raman scattering in extreme conditions of temperature and pressure, together by applying a gate.

Our goal is to discuss the universality of the detection of such mode. Technical Facilities: Glove Boxes for 2D

system exfoliation, Raman and transport measurements, clean room for contacting, High pressure cells,

cryogeny.


Collaboration between two teams of the Néel Institute (Nedjma Bendiab: Hybrid team, Pierre Rodière and

Marie-Aude Méasson: MagSup team). Theoretical collaboration with Lara Benfatto (ISC/Roma).

Collaboration with samples’ growers (Nantes, Spain). Networking: ANR project.

Possible extension as a PhD: YES.

Required skills: knowledge of condensed matter physics, curiosity, taste for delicate experiments.

Starting date: march-april 2019

Contact:

Name: Marie-Aude Méasson / Nedjma Bendiab / Pierre Rodière - Institut Néel - CNRS

e-mail: [email protected] / [email protected] / [email protected]

Fig. 1: Free energy of the superconducting state versus

the superconducting order parameter (Re(Δ),Im(Δ)).

There are two types of fundamental collective

excitations. One, the amplitude Higgs mode, is the

analogous of the Higgs boson.

Fig. 2 : Raman spectra of NbSe2, a compound which

presents a charge-density-wave (CDW) mode and

may present a superconducting Higgs mode below

Tc~7K, as observed by Raman spectroscopy.






44

Search for new high Tc superconducting oxides

General Scope:

Unconventional superconductivity with high critical temperature (Tc) occurs by doping

two-dimensional (2D) compounds presenting an antiferromagnetic order with a high Néel

temperature (TN) and a moderate magnetic moment. This is linked to the strong exchange

interaction, responsible for antiferromagnetism but also for superconductivity. This is the case

for cuprates and iron-based chalcogenides or arsenides. Thus a reasonable strategy to find new

superconductors, based on a spin fluctuations mechanism, is to select materials with these

properties, synthesize them and chemically dope them. In particular chromium compounds are

known to have strong antiferromagnetism. These low dimensionality oxides are difficult to

synthesize, which is an important obstacle, but also allows us to be among the first to study

them recently and to understand their physics. This can be very rich, regardless of whether or

not superconductivity is obtained (Kondo Orbital effect in CrSe2 [M. Núñez et al. Phys. Rev. B.

88 (2013)]; Quantum fluctuations at 600 K in CrRe [D. Freitas et al. Phys. Rev. B. 92 (2015)]).

Even if few years ago, thinking about finding superconductivity in chromium compounds made

experts sceptical, its discovery in CrAs under pressure [Wu Wei et al. Nature Comm. 5 (2014)],

now allows to expand this type of study.


We propose to perform the doping of the

Ruddlesden-Popper Æn+1CrnO3n+1 series

(where Æ is an alkaline earth, see figure) by

adequate chemical substitution. We have

already synthesized the parent phases n = 1, 2

and 3, and we have understood their physics,

thanks to a collaborative work between

experimentalists and theoreticians [Jeanneau

et al. PRL 118 (2017)]. The synthesis of these

oxides requires high pressure and high

temperature conditions, which are available in

the high-performance infrastructure of Institut

Néel. The crystallographic, electrical and magnetic properties, as well as the specific heat and

the thermal expansion of the doped samples will be probed thanks to the various experimental

setups available in our laboratory. Measurements under very high pressure, in particular

transport measurements, will complete the study.


Measurements using neutron scattering (ILL) and/or X-rays on synchrotron (ESRF) will also

be required in the medium term to understand the full set of properties. On the other hand, this

subject will benefit from interactions with the theoreticians of the laboratory or from abroad.

Possible extension as a PhD : Yes (via a selection organized by the Physics Graduate School).

Required skills : A good knowledge of the physics of condensed matter is desired.

Starting date : April 2019.

Contact : TOULEMONDE Pierre and NUNEZ-REGUEIRO Manuel

Institut Néel - CNRS : 04 76 88 74 21, [email protected];

04 76 88 78 38, [email protected]






45

New Superconductors with Iron

General Scope:

Superconducting materials convey great promises for energy saving and storage, and for reducing

our carbon footprint. This is obviously related to the possibility of electric-current transport without

dissipation, and the reduction of mechanical friction by means of magnetic levitation. At present, they are

commonly used in medical applications where they enable the generation of high and stable magnetic

fields for magnetic resonance imaging (MRI). However, a major challenge for the actual take-off of an

everyday superconducting technology lies in the discovery of appropriate materials with high

superconducting transition temperatures (Tc) and also with cheap and non-toxic elements. The project is

to investigate the potential of FeSi as a novel building block for high temperature superconductivity. This

investigation is motivated by the recent observation by the French community including the Néel Institute

of superconductivity in LaFeSiH. In this context, the student will participate in the partnership among

Grenoble, Bordeaux and Caen, highly competitive at international level.

Research topic and facilities available: Historically, superconductivity was believed not to coexist with

magnetism. This was surprisingly shown to be wrong with discovery of superconductivity in Cu and Fe-

based superconductors, both exhibiting high Tc. In the Fe-based systems a new family has been discovered

(LaFeSiH) with Tc=10K and based only on cheap and non-toxic elements. Our collaborative team aims at

studying this family, increasing the Tc, and deepen our understanding on the relationship between

superconductivity, magnetism and the changes of structure that happen to appear in the Pressure-Temperature

phase diagram. The student will perform transport, magnetic, optics, X-Ray and eventually Large Facilities

measurements (ESRF) at ambient and under pressure on the new compounds grown at Bordeaux.

Experimental Facilities : cryogeny, high pressure, transport, magnetic and optics measurements.


Networking: ANR project obtained in 2018. Collaborations: 2 teams of the Néel Institute, Bordeaux,

Caen, ESRF, Italy/Belgium/USA (DFT calculations)

Possible extension as a PhD: YES.

Required skills: knowledge of condensed matter physics, curiosity, taste for delicate experiments.

Starting date: march-april 2019

Contact:

Name: Manolo Nunez-Reguiero



Fig. : New family of compounds we discovered in 2017 based

on Iron, a magnetic element, and Si (compared to the previous

families which required toxic/expensive elements such as As

or Se ). The resistivity versus temperature at different

magnetic field: we observe the superconducting transition at

about 10K. This family also has a complex phase diagram

under pressure which shows competing/coexisting electronic

orders (magnetism) together with superconductivity and

structural transition.



46

Superconducting quantum devices with topological edge channels

General Scope: Graphene is a 2D material that has attracted a considerable interest since its discovery

in 2005. Its gapless linear band structure that mimics massless Dirac fermions has led to the discovery

of a wealth of new exciting transport properties. Moreover, the possibility to engineer very high mobility

graphene devices in which electrons can travel in a ballistic fashion makes graphene the perfect

playground to investigate new quantum coherent phenomena in the quantum Hall regime, or when

coupled with a superconducting condensate.

Research topic and facilities available: Our

research focuses on coherent quantum

transport in ballistic devices. One of our main

objective is to couple topological edge

channels in graphene with superconducting electrodes to

realize topological Josephson junctions [1]. Topological edge

channels are one dimensional edge channels that emerge in

high quality graphene when a strong magnetic field drives the

system in the quantum regime. For this objective, our group

has develop state-of-the art fabrication process of high

mobility graphene devices by encapsulation of graphene

monolayers between insulating boron-nitride flakes [2], so-

called van der Waals heterostructures.

We have an open Master/PhD position to study hybrid devices

that couple superconducting electrodes with ballistic graphene

to realize superconducting quantum devices such as gate-

tunable Josephson junctions. The objective of the Master internship is to fabricate and perform

preliminary characterization by quantum transport measurements (down to T=0.01K and up to B=18T)

of high mobility graphene Josephson junctions made with a high critical-field superconductor

(amorphous indium oxide [3]). The capability of the superconducting electrodes to withstand a high

magnetic field will enable to make pioneer investigation of Josephson junctions and more advanced

devices in the quantum Hall regime under strong magnetic field (PhD research program).

[1] Joule overheating poisons the fractional ac Josephson effect in topological Josephson junctions.

Le Calvez, et al. arXiv:1803.07674 (2018)

[1] Tunable transmission of quantum Hall edge channels in split-gated graphene devices. K.

Zimmermann, et al. Nature Communications 8:14983 (2017)

[3] Low temperature anomaly in disordered superconductors near Bc2 as a vortex glass properties. B.

Sacépé et al. arXiv:1609.07105 Nature Physics in press (2018)

Possible extension as a PhD: YES (supported by an EU grant)

Required skills: We look for highly motivated students with a good background in condensed matter

physics / quantum physics, and which are willing to address fundamental questions at the frontier of

quantum solid-states physics. Notice that lab visits are highly encouraged.


Contact: SACEPE Benjamin ( [email protected] )

Website: http://sacepe-quest.neel.cnrs.fr/

Figure | Left, SEM picture of graphene Josephson junctions devices. Right, differential resistance of a junction showing a superconducting branch (black area) that is modulated by a back gate electrode voltage Vg.

https://arxiv.org/abs/1803.07674

https://www.nature.com/articles/ncomms14983






47

Localized Cooper-pairs in disordered superconductors

General Scope: When a superconducting disordered thin film

is subjected to an increase of disorder or to a strong magnetic

field (B) it can undergo a transition to an insulating state. This

transition is a quantum phase transition occurring at T=0

between two antinomic ground states: The superconducting

and insulating ground states. The fundamental question

underlying this superconductor-insulator transition (SIT) is

whether Cooper pairing responsible for superconductivity dies

out at the critical disorder (or B), or survives beyond, that is, in

the insulating state. In recent years a body of work has shown

that in some amorphous superconductors the Cooper pairing

actually persists in the insulator, forming a new sort of

insulator called “Cooper-pair insulator”. The unusual nature of

this insulator and of the superconducting state that precedes it

is nowadays drawing considerable interest.

Research topic and facilities available: Our research

program focuses on both the superconducting and insulating

sides of the transition. We study mainly amorphous indium

oxide [1,3] and molybdenum-germanium thin films and

nanowires [2]. The goal of this Master project will be to

investigate the role of Coulomb interaction in the suppression

of the critical temperature of thin films. We will use our know-how in van der Waals heterostructures

to exfoliate flakes of insulating boron-nitride (BN) on a high dielectric constant substrate. E-beam

lithography will be carried out to design samples on micron size flakes. By varying the thickness of the

BN microcrystal, we will vary the distance to the high dielectric constant substrate that serves as a

screening plate, and thus tune the strength of Coulomb interactions. This study will provide crucial

information on the role of correlations and charging effects in the suppression of Tc and the formation

of the Cooper-pair insulator. For the PhD perspective, efforts will be focused on two important

objectives; i) investigating the critical point of the B-tuned SIT, and ii) performing innovative high

frequency measurements of the dielectric properties of the Cooper-pair insulator using state-of-the-art

superconducting micro-wave resonators.

[1] Localization of preformed Cooper pairs in disordered superconductors, B. Sacépé et al. Nature Physics 7,

132 (2011). arXiv:1012.3630

[2] Pair-breaking quantum phase transition in superconducting nanowires. H. Kim et al. Nature Physics AOP

(2018)

[3] Low temperature anomaly in disordered superconductors near Bc2 as a vortex glass properties. B. Sacépé et

al. arXiv:1609.07105 Nature Physics in press (2018)


Required skills: We look for highly motivated students with a good background in condensed matter

physics / quantum physics, and w hich are willing to address fundamental questions at the frontier of

quantum solid-states physics. Notice that lab visits are highly encouraged.


Contact: SACEPE Benjamin ( [email protected] )

Website: http://sacepe-quest.neel.cnrs.fr/

Figure | The SIT is easily tuned in experiments by applying a strong perpendicular magnetic field to a thin superconducting films. The figure shows a typical B-tuned transition from superconductor at B=0 to the Cooper-pair insulator at finite B with a diverging resistance at the lowest T.

http://arxiv.org/abs/1012.3630

https://www.nature.com/articles/s41567-018-0179-8






48

Search for new high Tc iron-based superconductors

General Scope:

The mechanism of high Tc superconductivity remains an open question in condensed matter

physics. Such superconductors show record Tc values of 135K for Cu-based families and 55K

for iron-based arsenides and chalcogenides (and even above 77-100K in FeSe monolayer) at

ambient pressure. The electron-phonon coupling is too weak in these layered materials to

explain their high Tc, other mechanism such as spins fluctuations has to be involved. In 2014

superconductivity was evidenced in in another Fe-based superconductor, YFe2Ge2 [Zou et al.

Phys.Stat.Sol. 8 (2014), see first figure], showing also Fe in tetrahedral coordination (with Ge).

Very recently, thanks to collaboration between

ICMCB and Néel Institute, superconductivity at

Tc~10K has been discovered in LaFeSiH (see

second figure), i.e. an analogous layered compound

without toxic element like arsenic [Bernardini et al.

PRB: Rapid Comm. 97 (2018)). A long term

project, involving our laboratory and starting in

December 2018, aims to extend this new FeSi-

based superconducting family and understand their

properties.


During this M2 internship we propose to use a high pressure – high

temperature process to 1) directly synthesize LaFeSiH from

precursors such as LaH3 (or anthracene as H source), La, LaSi,

Fe or FeSi, then 2) to try the Si substitution by Ge and H

substitution by F or O substitution and 3) possibly extend the

work to the study the related (Y,Ca)Fe2(Ge1-xSix)2 solid solution.

The crystallographic, electrical and magnetic properties, as well

as the specific heat of the different samples will be probed thanks

to the various experimental setups available in our laboratory.

Measurements under very high pressure, in particular transport

measurements, will complete the study.


Since the discovery of superconductivity in iron-based compounds, an important knowledge of

this family has been developed in our laboratory. The candidate will benefit of it and will have

the opportunity to interact with several collaborators at NEEL Institute, in particular with

theoreticians, but also outside from Grenoble.

Possible extension as a PhD : Yes (via a selection organized by the Physics Graduate School).

Required skills : The candidate must have a good background in solid state physics, crystallography

and material science.

Starting date : April 2019.

Contact : TOULEMONDE Pierre and NUNEZ-REGUEIRO Manuel

Institut Néel - CNRS : 04 76 88 74 21, [email protected];

04 76 88 78 38, [email protected]






49

Search for superconductivity under pressure in mono and bi-layer

graphene

General Scope:

The multiplication of the studies on graphene have resulted in a large number of the new applications.

However, very few experimental studies have been performed on his electronic properties under

pressure. Certainly, few changes are expected under pressure on the graphene mono-layer as it is

extremely hard in the basal plane. However, in our preliminary measurements shown in the figure, it is

clear that the resistance of the graphene sample changes enormously under pressure due to doping

effects. We intend to optimize this doping under pressure to over-dope single layer graphene and attain

the level where it has been predicted to be a chiral

superconductor [Nature

Phys. 8 (2012) 158].

Furthermore, the physics

of bi-layers under pressure

is certainly very rich. For

example, two graphene

monolayers, stacked in a

Moiré pattern by a small

angle rotation, have been

recently shown to be

superconducting at low

temperatures [Nature

556(2018)43]. We plan to

study the effect of pressure

on the Tc of Moiré bilayers. Finally, Van-der-Waals

bonding between two layers of graphene is weak and should be sensitive to pressure, that will deform a

bi-layer of graphene towards a diamond symmetry. Theoretical calculations have predicted these

structures to be superconductors [PRL 111(2013)066804].

Research topic and facilities available: The subject of the internship will consist in a first stage in the adaptation, for its assembly in the high-

pressure cells, of the graphene single and double layer samples, synthesized in collaboration with V.

Bouchiat of the HYBRID Team. The student will thus acquire a solid experience in nanofabrication. He

will proceed then to make transport measurements as a function of temperature down to 1K in both

piston-cylinder systems (P<2GPa; with P. Rodière, MagSup team) and in Bridgman cells (<30GPa; with

M. Nunez-Regueiro and M-A. Measson MagSup Team). These measurements will enrich his knowledge

of electronic properties of two-dimensional materials.

Possible collaboration and networking: The student will collaborate with colleagues of different Néel Institute departments.


Required skills: Good knowledge of condensed matter physics, curiosity, taste for delicate

experiments

Starting date:march-april 2019

Contact:

Name: Manuel Núñez-Regueiro






50

Degradable organosilica nanoparticles for controlled drug delivery

Summary:

Porous organosilica nanoparticles will be prepared to be used as nanovehicles for controlled drug

delivery of anti-cancer drugs. Their structure will feature organic fragments that will be cleaved in

cancer cells, leading to the overall degradation of the nanoparticle after or concomitantly with the release

of the drug.

Detailed subject:

Periodic Mesoporous Organosilicas are attracting considerable attention for application in catalysis,

optics or drug delivery [1]. These materials of general formula O1.5Si-R-SiO1.5, where R is an organic

group, are obtained by the sol-gel hydrolysis-condensation of organo(trialkoxy)silanes in the presence

of surfactants. They advantageously combine organic fragments linking inorganic siloxane domains.

Recently, the first nanosized PMOs have been produced with variable mesoporous structures depending

on the nature of the organic linker [2]. These nano-PMOs are very promising for controlled drug

delivery, as they feature an important mesoporosity, but also an organic substructure allowing a strong

hydrophobicity, suitable to interact with lipophilic drugs.

The elimination of the nanoparticles after drug delivery is of major concern. Therefore, we recently

designed nano-PMOs containing S-S bonds that are easily cleaved in cells. This allowed to the

destruction of the nano-PMOs under biological conditions [3].

The aim of this Master 2 internship is to prepare and characterize new types of PMO nanoparticles that

would be degradable under biological conditions, and to evaluate their potential in controlled drug

delivery. The syntheses will be performed either in solution or by spray-drying.

References:

Croissant, J.; Cattoen, X.; Wong Chi Man, M.; Gallud, A.; Raehm, L.; Trens, P.; Maynadier, M.;

Durand, J.-O., Adv. Mater. 2014, 26, 6174-6180.

Croissant,J.; Mauriello-Jimenez,C.; Maynadier, M.; Cattoën, X.; Wong Chi Man, M.; Raehm, L.;

Mongin, O.; Blanchard-Desce, M.; Garcia, M.; Gary-Bobo, M.; Maillard, P.; Durand, J.-O. Chem.

Commun. 2015, 12324-12327.

This Master internship may be extended into a PhD within the same research subject.

Background and expected skills:

Good knowledge in characterization techniques (spectroscopies, microscopies) and basic knowledge

in molecular and sol-gel chemistry are required.

Expected starting date: feb 2019

Contact: CATTOEN Xavier

Institut Néel - CNRS : 04-76-88-10-42 ; [email protected]

More information on: http://neel.cnrs.fr



51

Controlled nucleation and growth of molecular nanocrystals for

biophotonics and advanced solid-state NMR General Scope: We develop the synthesis of highly fluorescent tracers for biological imaging based on

two-photon fluorescence scanning microscopy. These tracers (50-100 nm) are based on molecular

nanocrystals (NCs) constituted by a high number of molecules (105-106) allowing their good

photostability and high cross sections of absorption and fluorescence emissions. This leads to bright

tracers to increase fluorescence contrasts and 3D imaging in the depths of biological tissues. On the

other hand, the shaping of organic NCs in solutions allow to enhance the sensitivity (by several orders

of magnitude) and the resolution of a just emerging method of magnetic resonance spectroscopy called

Magic Angle Spinning - Dynamic Nuclear Polarization (MAS-DNP), developed at CEA-INAC

Grenoble. This MAS-DNP spectroscopy will be used for 3D structure determinations (NMR

crystallography) of many solid-state systems, which do not easily form large enough crystals (>100 m)

required for single crystal X-ray diffraction studies and cannot be easily isotopically enriched in 13C and 15N. Thus, such developments are highly relevant, especially for supramolecular systems, drugs, natural

products, self-assembled peptides/nucleotides… etc.

Research topic and facilities available: The objective will be to control the confined nucleation and

growth of molecular NCs in droplets of organic solvents. For that, different organic compounds will

be dissolved in solvents miscible with water (alcohols, THF, dioxane…). The resulting solutions will

be sprayed and suddenly dispersed in water. As water is generally a non-solvent for molecular phases,

the corresponding NCs will grow when the solvent droplets will be gradually mixed in water. We

recently made a step-forward in the control of this process by producing nanometer-sized crystals of

progesterone (around 50 nm in diameter) as shown by scanning electron microscopy in the figure

below. The goal is now to produce monodisperse initial droplets to obtain then narrow size

distributions of NCs (50-100 nm) by optimizing the nanocrystallization reactor and confined

nucleation conditions. The resulting NCs will be characterized by X-ray diffraction, electron

microscopies (SEM and TEM), dynamic light scattering, Raman and fluorescence spectroscopies. This

research is part of a highly challenging ERC (European Research Council) project on developments

of MAS-DNP spectroscopy. Indeed, we believe that our generic process will be widely applicable for

molecules exhibiting both a significant solubility in solvents miscible with water and a negligible

solubility in water, which is the case of a large number of organic compounds. Finally, we will plan to

couple this confined nanocrystallization method in solutions to sol-gel chemistry, in order to prepare

through a one-step process core-shell nanoparticles: fluorescent NCs surrounded by an amorphous

silicate crust for medical imaging applications (highly fluorescent tracers).

Nanocrystals of progesterone obtained from a methanol solution sprayed and injected in water.

Possible collaborations and networking: INAC-CEA, ENS Lyon, INSERM Lyon


Required skills: Solid-state and physical chemistry, basic knowledge on physicochemical and

structural characterizations of materials. Starting date: 2018-19

Contact : Alain Ibanez, Institut Néel, CNRS. Phone: 0476887805 e-mail: [email protected]





52

White phosphors for LED lighting prepared by sol-gel method

General Scope: White LED lighting (wLED) has become a major challenge for energy saving.

wLED involve a phosphor (phosphor-coated LEDs, pc-LEDs), to convert the initial diode emission in

white light. The defect-based luminescent materials are a promising alternative to lanthanide or

transition metal activators doped phosphors for a lot of applications due generally to their main

advantages of good thermal and chemical stabilities, tunable emission color and low-cost price. At

Institut Néel, we have developed for several years original lanthanide-free phosphors for wLED, which

are patented. These phosphors are amorphous yttrium aluminum borate micro-powders around the

YAl3(BO3)4 stoechiometry. The innovative nature of these powders is to produce a broad band of white

luminescence emission throughout the visible spectrum by excitation in the near UV (370-390 nm) due

to emitting centers trapped in the stable amorphous matrix. It is thus possible to produce comfortable

white light for eyes with excellent color rendering index. Recently, we have identified the nature of

emitting centers, which are small aromatic molecules formed during the thermal treatments. These

pioneering works published recently open up a field of research that is extremely promising from both

for fundamental works and applications: photoluminescence (PL) efficiency, colorimetric emission

quality and very good stability.

Research topic and facilities available: Based on these promising results, this project will be to

optimize the synthesis of metal aluminum borate powders by sol-gel route varying chemical factors.

Different metals with lower coordination number and stoichiometric ratios of molecular precursors

(allowing metal complexation and polymerization of organic-inorganic network) will be tested. The

change of chemical composition should enable both to adjust the width of the PL emission for better

colorimetry and to enhance the PL efficiency. The size, shape and composition of phosphors play a

considerable role in tailoring the optical properties of pc-LEDs. For this reason, a special effort will be

made to control the morphologies of these powders using a high pressure/temperature drying of

alcoholic gels under supercritical conditions, followed by thermal treatments in controlled atmosphere.

The obtained powders are characterized by various techniques, including X-ray diffraction, Differential

Thermal Analysis-Thermogravimetry coupled with Mass Spectrometry, infrared spectroscopy, Nuclear

Magnetic resonance, Scanning Electron Microscopy and Photoluminescence spectroscopy.

Amorphous YAB powders exhibit PL from blue

emission for powders calcined at 450 °C to broad

white PL for higher calcination temperature. Small

aromatic molecules providing from decomposition

of propionate ligands are trapped within the

inorganic matrix.

Possible collaboration and networking: Institut de Recherche Chimie-Paris ; INAC-CEA Grenoble


Required skills: Chemistry in solution, knowledge on physicochemical and structural characterizations of

material

Contact : Pr Gautier-Luneau Isabelle

Institut Néel – CNRS






53

Molecular spin devices for quantum processing

General Scope:

The realization of an operational quantum computer is one of the

most ambitious technological goals of today’s scientists. In this

regard, the basic building block is generally composed of a two-

level quantum system (a quantum bit). It must be fully controllable

and measurable, which requires a connection to the macroscopic

world. In this context, solid state devices, which establish electrical

connections to the qubit are of high interest. Among the different

solid state concepts, spin based devices are very attractive since

they already exhibit long coherence times.

Electrons possessing a spin 1/2 are conventionally thought as the natural carriers of quantum information, but

alternative concepts make use of the outstanding properties of molecular magnets as building blocks for

nanospintronics devices and quantum computing. Their spin benefit from longer coherence times compared to

purely electronic spins. In this context, our team combines the different disciplines of spintronics, molecular

electronics, and quantum information processing. In particular, we fabricate, characterize and study molecular

spin-transistor in order to manipulate[1] and read-out an individual spin[2] to perform quantum operations[3].

[1] S. Thiele, F. Balestro, R. Ballou, S. Klyatskaya, M. Ruben, W. Wernsdorfer, Science 2014.

[2] R. Vincent, S. Klyatskaya, M. Ruben, W. Wernsdorfer, F. Balestro. Nature 2012.

[3] C. Godfrin, R. Ballou, S. Klyatskaya, M. Ruben, W. Wernsdorfer, F. Balestro, Phys. Rev. Lett. 2018.

Research topic and facilities available: Nano-devices addressing single molecular spins will be designed and

reliable methods for their realization and caracterization will be developed. Our team has a strong experience

in molecular magnetism, nanofabrication, ultra-low noise transport measurements, microwave electronics and

cryogenic equipment. We propose to use molecular spins as platform to perform multiqubit algorithms. Single

molecular units are embedded in scalable electronic circuits and individual spin read out is performed by

molecular (or carbon-based) quantum dots. The key experiment will be the demonstration of two qubit gate to

complete the set of universal gates for scalable architectures. The student will fabricate the samples using the

clean room facilities of the Néel Institut. She/he will carry out the measurements of the device at very low

temperature (20mK), using one of the six fully equipped dilution refrigerators of the team, in order to create,

characterize and manipulate single spin using spin based molecular quantum dot.

Possible collaboration and networking: This multidisciplinary research field is based on years of

collaborations with teams from different scientific and technical cultures (cleanroom, technicians,

collaborations with chemists and theoreticians, ...), in the framework of European projects and different

national and regional funding.


Required skills: We are looking for a motivated student who is interested in experiments that are challenging

from the experimental point of view.

Starting date:

Contact: BALESTRO Franck, Institut Néel - CNRS - UGA


More information: http://neel.cnrs.fr/spip.php?rubrique51



54

Interfacing molecular spins with nanomechanical oscillators in the quantum

regime

General Scope: The spin degree of

freedom is a natural candidate to carry

quantum information. Because of a

generally weak coupling to its

environment, it benefits from long

lifetimes even in solid-state devices. The

counterpart of this natural isolation is the

challenge to engineer strong coupling

between distant spins, which is

fundamental requirement to perform

quantum computations [1]. Among the

various types of existing spin systems,

molecular spins have shown remarkable properties in transistor devices [2], and they have already been used

to perform basic quantum information processing tasks [3]. It is known that in a solid state context, the

dominant source of decay for molecular spins comes from the coupling to mechanical modes via spin-phonon

coupling [4]. These phonons could be seen as a nuisance, but they actually constitute an interesting degree of

freedom that has recently been intensely investigated in the field of circuit quantum electromechanics. Our

strategy is to take advantage of the natural spin-phonon coupling in molecular magnets and use phonons as a

resource to control and readout molecular spins on fast time scales, using the powerful circuit quantum

electromechanics techniques [5]. Such an interface could enable the coupling of distant molecular spins, but

also the coupling to other degree of freedom such as microwave and optical photons, superconducting qubit or

other spin systems.

[1] J. J. Viennot, M. C. Darthiail, A. Cottet, T. Kontos, Science 2015

[2] S. Thiele, F. Balestro, R. Ballou, S. Klyatskaya, M. Ruben, W. Wernsdorfer, Science 2014.

[3] C. Godfrin, K. Ferhat, R. Ballou, S. Klyatskaya, M. Ruben, W. Wernsdorfer, F. Balestro, Phys. Rev. Lett. 2018.

[4] M. Ganzhorn, S. Klyatskaya, M. Ruben, W. Wernsdorfer, Nature Comm. 2016

[5] J. J. Viennot, X. Ma, K. W. Lehnert, (under review) arXiv 1808.02673 2018

Research topic and facilities available: The purpose of this internship is to develop mechanical oscillators

made out of graphene or carbon nanotubes, which will maximize the spin-phonon coupling while being

embedded in superconducting microwave circuits compatible with quantum electromechanics techniques. Our

team has a strong experience in molecular magnetism, nanofabrication, microwave electronics and cryogenic

equipment. The student will design and fabricate devices, and will perform microwave measurements at

cryogenic temperatures (20 mK) using one of the fully equipped dilution refrigerators of the team.

Possible collaboration and networking: This multidisciplinary research field is based on years of

collaborations with teams from different scientific and technical cultures (cleanroom, technicians, theorists,

collaborations with chemists), in the framework of European projects and various national and regional

funding.

Possible extension as a PhD: Yes. PhD fellowship available.

Required skills: We are looking for a motivated student who is interested in learning a wide variety of skills

and being part of an experiment involving both technical and fundamental challenges.

Starting date: flexible

Contact: VIENNOT Jérémie ([email protected])

BALESTRO Franck ([email protected])



NOTES

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INTERNSHIP2018 - 2019

Institut NÉEL - CNRS

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Documents

2018 - 2019 - Institut Néelneel.cnrs.fr/IMG/pdf/brochure_stage_neel_2018_2019.pdf · 2018-09-10 · ASTR-0014-02), your mission will be to develop a new fabrication process of NdFeB