phase shift and control in superconducting hybrid structures taro yamashita学术.pdf

该【phase shift and control in superconducting hybrid structures taro yamashita学术 】是由【司棋】上传分享，文档一共【7】页，该文档可以免费在线阅读，需要了解更多关于【phase shift and control in superconducting hybrid structures taro yamashita学术 】的内容，可以使用淘豆网的站内搜索功能，选择自己适合的文档，以下文字是截取该文章内的部分文字，如需要获得完整电子版，请下载此文档到您的设备，方便您编辑和打印。.,–C,?,??a),MemberSUMMARYThephysicsandapplicationsofsuperconductingphaseSQUIDswithJosephsonjunctions[9].Torealizelarge-,ane?cientcontroloftheTheoperationprincipleofalmostallsuperconductingdevicesisrelatedtosuperconductingphaseinJosephsonjunctionsneedstobethesuperconductingphase,andane?,,newmethodstoshiftorcontrolthephasemayleadtothedevelopmentthephasesoftheJosephsonjunctionsareprimarilycon-ofnovelsuperconductingdeviceapplications,ic?,,amoree?cientnanofabricationtechniques,,followingadiscussionofthebasicapproachneedstobedevelopedforlarge-scalesystemsbe-physicsofphasepropagationandshiftsinhybridsuperconductingstruc-causeitisdi?culttopreciselycontrolmanyqubitphasestures,interestingphenomenaanddeviceapplicationsinphase-shiftedsu-,variouspossibilitiesforInthispaper,wereviewvariousapproachesforcon-πicallycontrollable0andjunctionsaretrollingthesuperconductingphasesinsuperconductinghy-presented;:superconductivity,superconductingspintronics,πjunction,,thebasicprinciplesofAndreevphaseshift,Josephsonjunctionre?ectionandtheJosephsone?ectaredescribedfromthepointofviewofasuperconductingphase;inaddition,in--icJosephsonjunctionsandd-,in-terestingphenomenarelatedtophase-shiftedsuperconduct-Amacroscopicphaseinsuperconductorsisakeyfeatureingsystemsarepresented,,,severalmethodstocontrolthesu-interestingphenomenarelatedtosuperconductingphasesurrent,spincurrent,appear,suchasAndreevre?ections[1]andtheJosephsonon??ect[2].Superconductingphasesplayessentialrolesinbothfundamentalphysicsanddeviceapplicationsofsu---?ectionyears,suchassuperconductingquantuminterferencede-vices(SQUIDs)[3],rapidsingle?uxquantum(RSFQ)ursatnor-//circuits[4],andJosephsonvoltagestandardsystems[5].Al-malmetalsuperconductor(NMSC)interfaces,asshowninmostallsuperconductingdevicesoperatebyutilizingthesu-(a)[1].Whenavoltagesmallerthanthesupercon-,anelectronintheNMInrecentyears,superconductorshaveonceagainat-movestotheinterfacebutcannotentertheSCasanelectrontractedalotofattentionbecausesuperconductor-basedbecausethereisnoenergystatewithinthegapexceptacon-quantumbits(qubits)arepromisingcandidatesasbasicel-,theelectrontakesputingsystems[6]–[8].AlthoughanotherelectronwithoppositespinfromtheNMandformsthereareseveraltypesofsuperconductingqubits,,theinjectedelectronisre?ectedcharge,?ux,phase,andtransmonqubits,thebasicelementtotheNMasahole,;thisistheAndreevre??ection,θprisearraysofdirect-currentthere?ectedholeobtainsthesuperconductingphase((a))intheSC;asaresult,theinformationconcerningManuscriptreceivedOctober13,,.?TheauthoriswithNICTAdvancedICTResearchInstitute,icmetal/superconductor(FM/SC)in-Kobe-shi,651–2492Japan.??terface,theprobabilityofanAndreevre?ectionisverysen-TheauthoriswithPRESTO,JapanScienceandTechnologyAgency,Kawaguchi-shi,332–[10].Letusconsidera)E-mail:******@-metallicFMinwhichonlyanup-DOI:.((b)).Inthiscase,Copyrightc2018TheInstituteofElectronics,municationEngineersYAMASHITA:(a)icπjunctionand(b)d-?erence(?)intheSCs:J=JCsin?,whereJCistheJosephsoncriticalcurrent[2].TheJoseph-??ectionandcrossedAndreevre?ec-urrenceofmultipletionin(a),(b)and(c),(d),respectively.(a)and(c)arefornormalAndreevre?ectionsinabarrierlayer[14].Asdescribedmetal/superconductor(NM/SC)structures,and(b)and(d)areforferro-above,thesuperconductingphasepropagatesbyelectrons/superconductor(FM/SC)?ection,-sult,discreteAndreevboundstatesthatdependonthephaseaninjectedelectronwithanupspincannotobtainadown-di?erencebetweentwoSCsforminthejunction,andthespinelectronfromtheFM;thismeansthattheformationofJosephsoncurrent?,icessmallerforstrongerFMs,and(SC/FM/SCjunction),theAndreevboundstatesaremodu-thespinpolarizationofFMscanbeestimatedbymeasuringlatedbytheexchangeenergyintheFMandthereforebe-theconductanceviatheAndreevre?ection[10].comespin-dependentbecausetheFermiwavenumbersofThephasepropagationviatheAndreevre?ectionalsothepropagatingelectronsandholesarespin-dependentinoccursinnon-localstructures,(c)[11]–aFM[15].Asaresult,onditionsoftheex-[13].Inthisstructure,whenthedistancebetweentwoNMchangeenergyandthicknessoftheFM,thenumbersoftheelectrodesissmallenough[13]andanelectroninoneelec-AndreevboundstatesforpositiveandnegativeJosephsontrodeisinjectedintotheSC,theholecanbere?ectedontocurrentsarereversed;thus,thesignoftheJosephsoncriti-“crossed”Andreevre-calcurrentchanges,andthecurrent–phaserelationshipfor?ection(CAR).Inthisprocess,theinjectedelectronandthetheSC/FM/SCjunctionisshiftedbyπ;J=?JCsin?=?re?ectedholepropagateindierentNMelectrodes,buttheyJCsin(?+π).Thisjunctioniscalleda“πjunction,”?erenceisπinthegroundstate(πstate)[16].Theindicatesthatthephaseispropagatednon--electrodesareintheFM,theprobabilityofCARdependscillationoftheorderparameterintheFM[17].BecauseofizationsintheFMs:theexchangeenergyinFMs,themomentaoftheup-spinforexample,inthecaseofhalf-metallicFMs,aCooperanddown-spinelectronsinCooperpairshave?nitecentersizationsareparallelbe-,aspatialoscillationtermappearsincauseanup-spinelectroninoneelectrodecannotobtainatheorderparameterintheFM,andthephasedi?erenceofπdown-,esstablewhenthesignoftheorderparameterisdif-izationsareantiparallel,(d),?rstexperimentaldemon-anup-spinelectroninoneelectrodecanobtainadown-spinstrationofaπjunction,manystudiesontheπstatehaveelectronintheotherelectrode;asaresult,aCooperpairbeenpresented[18]–[24].Theordinarystate,,thecon-phasedi?erenceiszero(0state),andtheπstatecanbeductanceandresistanceofCARprocessesarehigherandsetbycontrollingthetemperatureandthicknessofaFMlower,respectively,forantiparallelalignmentsthanforpar-layer[18],[19].allelones;o-resistancee?ectsThesimplestgeometry,inwhichthephaseshiftbytheurinsuchsystems[13].πstateappearsasamacroscopicphenomenon,isasuper-conductingloopwithaπjunction,(a).,aspontaneouscir-ItiswellknownthattheJosephsone?ectappearsinsys-culatingcurrent?ows;ic?uxcorre-temsseparatedbytwoSCs,suchasSC/insulator/SCorspondingtoahalf-integer?uxquantumbeinggeneratedinSC/NM/SCjunctions,andtheJosephsoncurrent(J)de-.,–C,-wavepairingsymmetryoftheordertionwassatis?edfortheπphasedi?erencesofallthejunc-parameter,whichoftenappearsinhigh-transitiontempera-,a?nitecurrentspontaneously?owedinture(high-TC)superconductors,suchasYBCO[25]–[27].theloopwithoddnumbersofπjunctionsbecausethephaseInd-wavesymmetry,thepositiveandnegativelobesaresep-di?erencesofeachjunctionshiftedfromπtosatisfythe?(b),,aπTheauthorsmeasuredthespontaneouscurrentsinthephaseshiftisgeneratedintheloop,andaspontaneousmag-variouspatternofthearrayswiththe“frustrated”(oddπnetic?uxisgeneratedinthesamemannerasitisinafer-junctions)and“unfrustrated”(evenπjunctions),forascanningSQUIDmicroscope(SSM).Figure3(c)showsicJosephsonjunctionsandd-wavepairinganSSMimageofa6×6checkerboard-frustratedarrayatsymmetry,the0andπstatescannotbecontrolledexternally,–πtran-.,ic?eld,,?exibly,therefore,junctionswereinthe0state,sonospontaneouscurrentsap-somespeci?cstructuresneedtobeprepared;thesearepre-,spontaneouscurrentsstartedto?owinthecells,ic?uxpatternappearedinthearraybe--,?uxarrayisattractiveforstudyingthefrustratedtwo-dimensionalsys-Aninterestingexperimentregardingphase-shiftedsuper-tems[29].conductingsystemswithπjunctionshasbeendemonstratedbyFrolovetal.[28].-Oneimportantapplicationofsuperconductorsisincryo-puting[4],[30]–[33].Recently,varioustypesofJosephsonjunctions,(a)and(b),respec-superconductinglogicdeviceshavebeendevelopedascan-(CuNi)layerwasdidatesforpost-puters,suchasRSFQ[4],[30],setto11nm,forwhichtheJosephsonjunctionchangestoadiabaticquantum?uxparametron(AQFP)[31],[32],-reciprocalquantumlogic(RQL)[33]-,nocurrentvantagesofthesesuperconductinglogicdevicesaretheir?owedintheloopcontainingevennumbersofπjunctionshigh-;urredbecausethe?uxquantiza-example,RSFQcircuitscanoperateontheorderof10–100GHz[30],andanAQFPhasbeendemonstratedtohaveapowerconsumptionof10zJ[32].Notonlydothesede-viceshavepotentialforuseinhigh-putingsystems,buttheRSFQandAQFPcircuitsarealsoexpectedto?nduseascryogenicsignal-processingcircuitsforsu-perconductingnanowiresingle-photondetectors(SSPDsorSNSPDs)[34],[35].E?cientphaseshiftandcontrolarecrucialforimprov-,thereisaproblemassociatedwithalargesingle-?uxstoragecellbecausehighgeomet-(a)anunfrustratedand(b)afrustratedsupercon-ductingcellwithπjunctions.(c)SSMimageofa6×6checkerboard--junction?,fromthetop,,,?eldscaleisapproximatelyinunitsofmΦ0[28].ic?:PHASESHIFTANDCONTROLINSUPERCONDUCTINGHYBRIDSTRUCTURES381ic?uxquan-,developingquietqubitswithd-