TOPOLOGICAL MATTER

Distinguishing a Majorana zero modeusing spin-resolved measurementsSangjun Jeon1 Yonglong Xie1 Jian Li123 Zhijun Wang1

B Andrei Bernevig1 Ali Yazdani1dagger

One-dimensional topological superconductors host Majorana zero modes (MZMs) thenonlocal property of which could be exploited for quantum computing applications We usespin-polarized scanning tunneling microscopy to show that MZMs realized in self-assembledFe chains on the surface of Pb have a spin polarization that exceeds that stemming from themagnetism of these chains This feature captured by our model calculations is a directconsequence of the nonlocality of the Hilbert space of MZMs emerging from a topologicalband structure Our study establishes spin-polarization measurements as a diagnostic tool todistinguish topological MZMs from trivial in-gap states of a superconductor

LocalizedMajorana zeromodes (MZMs) arenon-Abelian quasiparticles that emerge atthe ends of one-dimensional topological su-perconductors and may be used as buildingblocks for future topological quantum com-

puters (1ndash3) A variety of condensedmatter systemscan be used to engineer topological supercon-ductivity and MZMs (4ndash7 ) To date evidence forMZMs has come from experiments that have de-tected their zero-energy excitation signature invarious spectroscopicmeasurements (8ndash10) How-ever despite the recent progress the question asto whether a MZM could be distinguished from afinely tuned or accidental trivial zero-energy edgestate in these experiments has been unresolved(11ndash13) The interpretation of the experimentallyobserved zero-energymodes as MZMs in variousplatforms has relied so far on showing that thezero-energy mode is detected when the param-eters of the system make it most likely to be ina topological superconducting phase Althoughthere is intense interest in using such modes tocreate topological qubits [for example (14)] ar-guably a unique experimental signature ofMZMs has yet to be reported Here we describehow spin-polarized spectroscopicmeasurements(15ndash21) can be used to distinguish MZMs fromtrivial localized quasiparticles by identifying ex-perimental features that are a direct consequenceof the nonlocality of the Hilbert space of MZMsemerging from a topological band structurePrevious studies have provided strong evidence

that combining ferromagnetism in chains ofFe atoms with the large spin-orbit coupling in-teraction of the Pb(110) surface onwhich they areself-assembled gives rise to a proximity-inducedtopological superconducting phase This phaseexhibits strongly localized MZMs at both ends ofthese chains (9 22ndash24) High-resolution scanning

tunneling microscopy (STM) studies have directlyvisualized MZMs placed a stringent bound ontheir splitting (lt45 meV) shown evidence for thepredicted equal electron-hole spectral weightusing spectroscopy with superconducting tipsprovided a detailed understanding of their spatialprofile and revealed the robustness of their sig-natures when the Fe chains are buried by thedeposition of additional superconducting mate-rial on top (25) Because trivial zero-energy local-ized states may still show some of the featuresattributed to MZMs we turned our attention tospin-polarized measurements of this systemWe performed spin-polarized STM (SP-STM)

measurements (26) of self-assembled Fe chainsby using Fe-coated Cr tips which although fer-romagnetic at their apex do not have strongenough magnetic fields to disrupt the supercon-ductivity of the Pb(110) substrate [Fig 1A fig S1and section 1 of (27)] Before making measure-ments in zero applied magnetic field the tiprsquosmagnetization is first trained in situ with theapplication of a magnetic field that is either par-allel (P) or antiparallel (AP) to the vector normalto the surface We have found that the observa-tion of the hard Bardeen-Cooper-Schrieffer (BCS)gap in the Pb substrate can be used to deducewhether or not trapped flux exists in our super-conducting magnet Often by adding a smallcompensation field (~5 or ndash5 mT) the trappedflux can be canceled before proceeding with thespin-polarization measurement (fig S2) The fieldtraining switches the orientation of the STM tiprsquosmagnetization relative to that of the Fe chains(28) which results in a change of the apparentheight of the chains and a uniform shift of thetopographic features as shown in Fig 1 B to D(see also fig S5) The observation of two types ofcontrast in topographs of many different chainswith the same spin-polarized tip confirms theferromagnetic behavior of our chains (figs S3and S4) The height difference in the topo-graphs reflects the difference between the ldquouprdquoand ldquodownrdquo spin-polarized density of normalstates ethruarrN rdarrNTHORN of the chains near the Fermi en-ergy (EF) the integral of which (between EF and

voltage bias eVB) is related to the tunneling cur-rent which is kept constant by the STM feedbackloop This compensation of drN frac14 ruarrN rdarrN by theso-called STM set-point effect for eVB close to EFis best demonstrated by the spectroscopic mea-surements [G(V ) = dIdV |eV=E ordm r(E)] of the Fechains such as in Fig 1E where a small 100-mT(out-of-plane) magnetic field is used to suppresssuperconductivity in Pb and Fe chains (G differen-tial conductance V voltage I current) The spectrameasuredat all locations on the chainsnearEFwithboth tip orientations [GP(V ) GAP(V )] are equalbecause the average spin polarization is com-pensated by adjusting the tip height for the twospectra [figs S6 to S8 and sections 2 to 4 in (27 )]It is possible to avoid this compensation and toartificially enhance the influence of spin polar-ization on G(V ) by choosing a set-point bias thatis further from EF [figs S1 and S3 and section 1 of(27 )] Previously we have used this approach todemonstrate that our Fe chains are ferromagneti-cally ordered [30 meV in (9)] However for thepurpose of the current study we focused on asmall bias window near EF where the normalstate spin-dependent contribution is compensatedby the STMset-point effect As shown inFig 1F theSTM-measured spin polarization P(E) = [GP(E) ndashGAP(E)][GP(E) + GAP(E)] is zero over an energywindow of plusmn5 meV Repeating the same mea-surements in the superconducting state there-fore allowed us to detect whether low-energyquasiparticle states show any spin polarizationbeyond that caused by the ferromagnetism of ouratomic chainsOur finding that the MZM shows a distinctive

spin signature is demonstrated by measurementsof the spin-polarized zero-bias conductance GP(0)andGAP(0)maps of the atomic chains in zeromag-netic field (Fig 2) The ldquodouble-eyerdquo spatial struc-ture of the MZM in such high-resolution mapsat zero bias near the end of Fe chains has beenpreviously measured with unpolarized tips (25)It is theoretically understood from model cal-culations that consider both the spectral weightof theMZM in the superconducting substrate andthe trajectory of the STM tip during the constantcurrent conductance map measurements Thedata in Fig 2 however show that the magnitudeof the MZM signature in GP(0) and GAP(0) mapsdepends on themagnetic polarization of the STMtip Moreover the contrast can be reversed byreorienting the tiprsquos magnetization or by exam-ining different chainswith different ferromagneticorientation [figs S9 and S10 and section 5 of(27 )] GP(0) and GAP(0) maps do not show anycontrast away from the end of the chain (dashedlines in Fig 2C) where the signal in the bulk ofthe chain is likely dominated by the backgroundfrom higher-energy quasiparticles in our systemowing to thermal broadening in our experiments(performed at 14 K) The spin contrast shown inFig 2 reproduced for many chains demonstratesthat the end zero mode in our system has a po-larization beyond the normal-state backgroundcaused by the magnetism of the chainsThe details of the spin dependence of the

tunneling conductance as a function of energy

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Jeon et al Science 358 772ndash776 (2017) 10 November 2017 1 of 5

1Joseph Henry Laboratories and Department of PhysicsPrinceton University Princeton NJ 08544 USA 2Institutefor Natural Sciences Westlake Institute for Advanced StudyHangzhou Zhejiang China 3Westlake University HangzhouZhejiang ChinaThese authors contributed equally to this work daggerCorrespondingauthor Email yazdaniprincetonedu

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and position throughout the chain can be foundin Fig 2 D to G which in addition to the spinpolarization of the edge-bounded MZM alsoshows the polarization of the other in-gap statesat higher energies These so-called Shiba statesinduced bymagnetic structures on superconduc-tors (29 30) are predicted to be spin-polarized(30 31) however their spin properties have notbeen experimentally detected To better charac-terize the spin polarization of both theMZM andthe Shiba states in spectroscopic measurementsin Fig 3 A and B we show averaged spectra atthe end and in the middle of the chain alongwith the spin polarization P(E) computed fromthese spectra In addition to the MZM spin-polarization signature as a peak at P(0) anotherkey finding is the antisymmetric behavior of P(E)

for Shiba states at higher energies These mea-surements demonstrate that the states with en-ergy |E| ltDPbwhereDPb is a superconducting gapshow features beyond those expected simply fromthe ferromagnetism of the chain the average po-larization of which is compensated by the STMset-point effect as described aboveThe first step in understanding that our spin-

polarizedmeasurements distinguish the presenceof the MZM in our system is to show that notrivial localized state can give rise to a signal inthe STM-measured P(E) at zero energy To illus-trate this point we consider a single magneticimpurity in a host superconductor (Fig 4A) whichgives rise to a localized Shiba state within thesuperconductorrsquos gap (DPb) at eV = plusmnE0 lt DPb(Fig 4B) We have recently computed the spin

properties of these states by using a model thatconsiders a magnetic quantum impurity (forexample a partially filled d level) coupled to ahost superconductor [(32) and section 6 of (27)]The changes in the superconducting hostrsquos nor-mal state ruarr=darrN induced by the magnetic impurityvia the exchange interaction determine thespin polarization of the Shiba state inside the

gapruarr=darrS ethETHORNfrac14 pruarr=darrN

ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiD2PbE2

0

qdethE∓E0THORN (Fig 4B)

From this result we see that the polarization of atrivial localized Shiba state tuned to zero energy(E0 = 0) is no larger than that of the normal-statepolarization induced by the magnetic impurityMoreover it can be shown by symmetry that thespin contrast in our constant current conduct-ancemeasurements [dG(E) =GP(E) ndashGAP(E)] forthe localized Shiba state must be antisymmetricas function of energy [dG(E) = ndashdG(ndashE)] whichmeans that there should be no spin contrast inspin-polarized STM measurements for E0 = 0Shiba states [(32) and section 6 of (27)] Our ob-servation of a spin contrast for the edge mode ofour atomic chains therefore excludes the possibil-ity that this zero-energy feature is causedpurely bya localized Shiba state at zero energy Because aShiba state caused bymagnetic impurities is theonly known trivial mechanism able to produce alocalized in-gapdifferential conductancepeak thatdisappears in the absence of superconductivity ourobservation of a localized peak in P(E) at zero en-ergy uniquely identifies the MZM in our chainsTo further show that our spin-polarization

measurements distinguish between trivial quasi-particle states and the topologicalMZM we com-pare our experimental results tomodel calculationsof chains of magnetic impurities embedded in asuperconductor [section 7 of (27)] A chain ofmag-netic atoms induces a band of Shiba stateswithinthe host gap which produces pairs of peaks at pos-itive andnegative bias in aG(V ) simulation (Fig 3C and D) The width of these peaks is related tothe bandwidth of the Shiba states and their dis-persion For simplicity we model a single Shibaband (Fig 3 C and D) but previously we haveshown that the shape of experimental spectra(Fig 3 A andB) is captured by amodel includingmultiple Shiba bands (25) The Shiba bands pro-duce signatures in spin-polarizedmeasurementsthat are very similar to that of a localized Shibastate Specifically the energy-antisymmetric fea-ture inP(E) thatwehave discussed above as beingthe hallmark of localized Shiba states also de-scribes the behavior of extended Shiba states de-tected both at the ends and in the middle of thechains (Fig 3 C and D) These features are re-produced in our experimental results (Fig 3 Aand B) and confirm our understanding of sig-natures in P(E) arising from the extended Shibastates in our chainsOur theoretical considerations of a hybrid chain-

superconductor system also reveal that a largerpolarization than that of the normal-state back-ground detected at zero energy in our experi-ments (Fig 3A) is a diagnostic signature of thenonlocal nature ofMZMs Unlike trivial localizedstates MZMs can only exist at the edge of a chain

Jeon et al Science 358 772ndash776 (2017) 10 November 2017 2 of 5

Fig 1 Spin polarization of Fe chains on Pb(110) at normal state (A) Schematic of the SP-STMmeasurement on a MZM platform probed by a FeCr tip whose magnetization can be controlledby an external magnetic field (red Fe orange Cr) (B) Topography of a typical Fe chain (chain 1)under zero magnetic field [set-point voltage (Vset) = 10 mV set-point current (Iset) = 750 pA](C and D) Height profile of chain 1 (C) and chain 2 (D) measured with the up-polarized tip (solidred curves) and down-polarized tip (solid blue curves) Dashed lines show the height profiles ofthe Pb substrate measured with both tips The positions of the topographic profiles are shown in (B)Insets show a magnification of the height profiles of the chains Red and blue dashed lines in theinsets show the average height of the chains measured with the up- and down-polarized tipsrespectively (E) Spectra measured in the middle of chain 3 at 100 mTwith up-polarized (red curve)

and down-polarized (blue curve) tips which correspond to GNP ethVTHORN and GN

APethVTHORN [Vset = ndash5 mV Iset =500 pA modulation voltage (Vmod) = 40 mV] (F) Calculated polarization of the spectra shown in (E)

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system with extended electronic states the prop-erties of which not only dictate the formation ofMZMs but also determine their spin polariza-tion as well as that of the normal-state back-ground Specifically MZMs appear at the edgesof ferromagnetic chains that have a normal-stateband structure with an odd number of spin-splitbands crossing EF The MZM in such chainsemerges from only one of the spin-polarizedbands at EF and in our case is associated withthe exchange-split d bands of the ferromagneticFe chains as schematically shown in Fig 4C Thelarge band splitting (~2 eV) between majorityandminority bands in the Fe chains estimated inour previous study (9 22) guarantees that theminority spin bands cross EF The spin polariza-

tion of the MZM (Fig 4D) is directly related tothe spin polarization of these specific momen-tum states at EF where the induced topologicalgap is opened although spin-orbit coupling re-sults in a very slight tilting of the spin polariza-tion away from the ferromagnetic magnetizationTo understand why this localized MZM spinpolarization can be detected in our STM mea-surements we must contrast the MZM polariza-tion with that of the normal-state backgroundwhich is compensated by the STM set-point ef-fect The normal-state background spin polar-ization of our system involves not only the Festates crossing EF but also states further awayin energy that are broadened owing to thehybridization with the Pb substrate (Fig 4 C and

D) The sum contribution of these delocalizedstates throughout the chain to the backgroundat its end is always smaller than that of a localizedMZM (32) Consequently as our calculations fora hybrid chain-superconductor system show(Fig 3C and 4D) the MZM spin polarizationexceeds that of the normal-state backgroundproviding an important test for the detection ofMZMs in our systemWe contrast the nature of the background rel-

evant to the MZM spin-polarization measure-ments with that of a trivial localized state whichmay accidently appear near the end at near-zeroenergy For such a localized state as in the case ofan isolated Shiba impurity (described above)the relevant normal-state background is local

Jeon et al Science 358 772ndash776 (2017) 10 November 2017 3 of 5

Fig 2 Spatially resolved spin-polarized states on a Fe atomic chain(A and B) Zero-energy conductance map near the chain end taken with up-polarized (A) and down-polarized (B) tips (Vset = ndash5 mV Iset = 500 pA Vmod =40 mV) The conductance at the double-eye feature taken with the up-polarized tip (A) is stronger than that at the same feature taken with thedown-polarized tip (B) (C) Line cuts taken from (A) and (B) as indicated bythe corresponding symbols Solid lines represent the conductance profileacross the double-eye feature measured with up-polarized (red curves) and

down-polarized (blue curves) tips Dashed lines show typical conductanceprofiles away from the chain end (D) Topographic image of chain 3 takenat zero external field (Vset = ndash10 mV Iset = 750 pA) (E and G) Spatial variationof the spectra taken along the white dashed line shown in (D) withup-polarized (E) and down-polarized (G) tips (Vset = ndash5 mV Iset = 500 pAVmod = 40 mV) (F) Individual spectra from (E) (red curves) and (G) (bluecurves) at the labeled location The end state appears at spectrum 3 (arbarbitrary)

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Jeon et al Science 358 772ndash776 (2017) 10 November 2017 4 of 5

Fig 3 Comparison of experimental data and SP-STS simulation (A andB) Experimentally obtained spectra at the end of the chain (A) and in themiddle of the chain (B) and their corresponding polarization (Vset = ndash5 mVIset = 500 pA Vmod = 40 mV) Yellow and blue curves were measured with up-and down-polarized tips respectively Red arrows mark the zero-energy

end state and black arrows mark the Van Hove singularity of the Shiba band(C and D) Simulated spectra at the end of the chain (C) and in the middleof the chain (D) and their polarization [section 7 of (27)] Experimental andsimulated results both show strong positive polarization for the end state andenergetically antisymmetric polarization for the Shiba states at higher energies

Fig 4 Single magnetic impurity and magneticchain model calculations (A and B) Model calcula-tion for a magnetic impurity hybridized with asuperconductor [section 6 of (27) describes themodel Hamiltonian used in this calculation M = 1m = 075 n = 04 D = 0001 h = 5endash6] The originald-orbital states of impurity are marked as dashedlines in (A) (red for the minority state and blue for themajority state) Solid curves represent the spindensity of states (DOS) of the hybridized impurity-superconductor system The width of DOS marked asprsV

2 is the broadening caused by the couplingbetween the magnetic impurity and the super-conductor [section 6 of (27)] A pair of Shiba statesinside a superconducting gap is shown in (B) Dashedlines in (B) correspond to the normal-state spinDOS of the minority state (red) and majority state(blue) which are the same value as the spin DOS atthe Fermi energy marked in (A) (C and D) Modelcalculation for a magnetic chain embedded in asuperconductor [section 7 of (27)] Solid curves in(C) are the dispersion of original d-orbital bands(red for the minority band and blue for the majorityband which are energetically split by the exchangeenergy 2M) The red dashed curve represents thehole copy of the minority band Black arrows markthe momenta where the minority band crosses theFermi level Spin DOS calculated at the end of thechain displayed in (D) show MZM and Van Hovesingularities of Shiba bands Red and blue dashedlines are normal-state spin DOS of minority andmajority bands respectively The inset shows thedispersion of Shiba bands kx is the wave vector along the magnetic chain

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resulting in compensation by the STM set-pointeffect and therefore showing no contrast in thespin-polarizedmeasurements A zero-energy peakin measurements of P(E) in spin-polarized STM(Fig 3A) is caused by the nonlocal nature of theMZM background and constitutes a unique sig-nature of these excitations allowing us to distin-guish them from trivial edge modesLooking beyond our atomic-chain Majorana

platform spin-selective spectroscopy measure-ments using quantum dots have been recentlyproposed for the semiconducting nanowireMajorana platform (33) As we have done in thisstudy for the atomic chains such experiments areexpected to distinguish between trivial and non-trivial edgemodes and probe the nonlocal natureof MZMs in the nanowire platform The spin po-larization of MZMs may provide a useful ap-proach to creating highly polarized spin currentsand entangling these topological localized quan-tum states with conventional spin qubits In factthere are proposals outlining howahybrid systemof spin andMZM qubits can be used to performuniversal quantum computation (34) The possi-bility that electron tunneling between spin qubits(based on quantum dots or individual defects)and MZMs can realize a quantum superpositionbetween the two is intriguing Such a processcould for example facilitate long-distance entan-glement between spatially well-separated spinqubits (35 )Note added in proof After submission of our

manuscript a spin-polarized STM study of Cochains on Pb(110) was reported (36) The spinpolarization of the Shiba bands on such chainsalso shows the antisymmetric features (with bias)and is consistent with our results and analysis

REFERENCES AND NOTES

1 A Y Kitaev Phys Uspekhi 44 131ndash136 (2001)2 C Nayak S H Simon A Stern M Freedman S Das Sarma

Rev Mod Phys 80 1083ndash1159 (2008)3 C W J Beenakker Annu Rev Condens Matter Phys 4

113ndash136 (2013)4 L Fu C L Kane Phys Rev Lett 100 096407 (2008)5 Y Oreg G Refael F von Oppen Phys Rev Lett 105 177002

(2010)6 R M Lutchyn J D Sau S Das Sarma Phys Rev Lett 105

077001 (2010)7 S Nadj-Perge I K Drozdov B A Bernevig A Yazdani Phys

Rev B 88 020407 (2013)8 V Mourik et al Science 336 1003ndash1007 (2012)9 S Nadj-Perge et al Science 346 602ndash607 (2014)10 S M Albrecht et al Nature 531 206ndash209 (2016)11 E J H Lee et al Nat Nanotechnol 9 79ndash84 (2014)12 R Žitko J S Lim R Loacutepez R Aguado Phys Rev B 91

045441 (2015)13 M T Deng et al Science 354 1557ndash1562 (2016)14 D Aasen et al Phys Rev X 6 031016 (2016)15 D Sticlet C Bena P Simon Phys Rev Lett 108 096802 (2012)16 J J He T K Ng P A Lee K T Law Phys Rev Lett 112

037001 (2014)17 A Haim E Berg F von Oppen Y Oreg Phys Rev Lett 114

166406 (2015)18 K Bjoumlrnson S S Pershoguba A V Balatsky

A M Black-Schaffer Phys Rev B 92 214501 (2015)19 P Kotetes D Mendler A Heimes G Schoumln Physica E Low

Dimens Syst Nanostruct 74 614ndash624 (2015)20 H H Sun et al Phys Rev Lett 116 257003 (2016)21 P Szumniak D Chevallier D Loss J Klinovaja Phys Rev B

96 041401 (2017)22 J Li et al Phys Rev B 90 235433 (2014)23 M Ruby et al Phys Rev Lett 115 197204 (2015)24 R Pawlak et al NPJ Quantum Inf 2 16035 (2016)25 B E Feldman et al Nat Phys 13 286ndash291 (2016)26 R Wiesendanger Rev Mod Phys 81 1495ndash1550 (2009)27 Supplementary materials28 Fe chains have a higher coercive field (gt6 T) and their

magnetization cannot be switched by applying a 1-T training field29 A Yazdani B A Jones C P Lutz M F Crommie D M Eigler

Science 275 1767ndash1770 (1997)30 A V Balatsky I Vekhter J-X Zhu Rev Mod Phys 78

373ndash433 (2006)

31 C P Moca E Demler B Jankoacute G Zaraacutend Phys Rev B 77174516 (2008)

32 J Li S Jeon Y Xie A Yazdani B A Bernevig The Majoranaspin in magnetic atomic chain systems arXiv170905967[cond-matmes-hall] (18 September 2017)

33 E Prada R Aguado P San-Jose Phys Rev B 96 085418 (2017)34 S Hoffman C Schrade J Klinovaja D Loss Phys Rev B 94

045316 (2016)35 M Leijnse K Flensberg Phys Rev Lett 107 210502 (2011)36 M Ruby B W Heinrich Y Peng F von Oppen K J Franke

Nano Lett 17 4473ndash4477 (2017)

ACKNOWLEDGMENTS

We acknowledge discussions with L Glazman F von OppenK Franke P Lee and C Kane This work has been supported by theGordon and Betty Moore Foundation as part of the EPiQS initiative(GBMF4530) the Office of Naval Research (grants ONR-N00014-14-1-0330 ONR-N00014-11-1-0635 and ONR-N00014-13-1-0661) NSFMRSEC (Materials Research Science and Engineering Centers)programs through the Princeton Center for Complex Materials (awardDMR-1420541) NSF award DMR-1608848 a Simons InvestigatorAward NSF EAGER (Early-concept Grants for Exploratory Research)award NOA-AWD-1004957 the Department of Energyrsquos Office ofBasic Energy Sciences the Packard Foundation Army ResearchOffice MURI (Multidisciplinary University Research Initiatives) programW911NF-12-1-046 and the Eric and Wendy Schmidt TransformativeTechnology Fund at Princeton The single magnetic impurity andmagnetic chain model calculations in this work were supportedby Department of Energy grant DE-SC0016239 This project was alsomade possible by the facilities at Princeton Nanoscale MicroscopyLaboratory BAB thanks Ecole Normale Superieure UPMC(Universiteacute Pierre et Marie Curie) Paris and Donostia InternationalPhysics Center for their generous sabbatical hosting AY acknowledgesthe hospitality of the Aspen Center for Physics supported by NSFaward PHY-1607611 The data presented in this paper are availablefrom the corresponding author upon reasonable request

SUPPLEMENTARY MATERIALS

wwwsciencemagorgcontent3586364772supplDC1Materials and MethodsSupplementary TextFigs S1 to S10

3 April 2017 accepted 29 September 2017Published online 12 October 2017101126scienceaan3670

Jeon et al Science 358 772ndash776 (2017) 10 November 2017 5 of 5

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Distinguishing a Majorana zero mode using spin-resolved measurementsSangjun Jeon Yonglong Xie Jian Li Zhijun Wang B Andrei Bernevig and Ali Yazdani

originally published online October 12 2017DOI 101126scienceaan3670 (6364) 772-776358Science

this issue p 772Sciencesignalsignature of the topological states Unlike trivial zero-energy states MBS exhibited a characteristic spin-polarization

studied chains of iron atoms deposited on superconducting lead and found a more distinctiveet alspectroscopy Jeon at zero energy but mechanisms other than MBS need to be carefully ruled out Using spin-polarized scanning tunnelingcomputing has been found in several material systems Typically the experimental signature is a peak in the spectrum

Evidence for Majorana bound states (MBS) which are expected to provide a platform for topological quantumTopological or trivial

ARTICLE TOOLS httpsciencesciencemagorgcontent3586364772

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REFERENCES

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is a registered trademark of AAASScienceScience 1200 New York Avenue NW Washington DC 20005 The title (print ISSN 0036-8075 online ISSN 1095-9203) is published by the American Association for the Advancement ofScience

Science No claim to original US Government WorksCopyright copy 2017 The Authors some rights reserved exclusive licensee American Association for the Advancement of

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