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1、PHYSICALREVIEWX2,031004(2012)Graphene-BasedHeterojunctionbetweenTwoTopologicalInsulators111,2121OleksiiShevtsov,PierreCarmier,CyrilPetitjean,ChristophGroth,DavidCarpentier,andXavierWaintal1CEA-INAC/UJFGrenoble1,SPSMSUMR-E9001,GrenobleF-38054,France2CNRS—Laboratoiredephysique,Eco
2、leNormalesupe´rieuredeLyon,France(Received24January2012;published19July2012)QuantumHall(QH)andquantumspinHall(QSH)phaseshaveverydifferentedgestatesand,whengoingfromonephasetotheother,thedirectionofoneedgestatemustbereversed.Westudythisphenomenoningrapheneinthepresenceofastrongpe
3、rpendicularmagneticfieldontopofaspin-orbit(SO)-inducedQSHphase.Weshowthat,belowtheSOgap,theQSHphaseisvirtuallyunaffectedbythepresenceofthemagneticfield.AbovetheSOgap,theQHphaseisrestored.AnelectrostaticgateplacedontopofthesystemallowsthecreationofaQSH-QHjunctionwhichischaracterize
4、dbytheexistenceofaspin-polarizedchiralstate,propagatingalongthetopologicalinterface.Wefindthatsuchasetupnaturallyprovidesanextremelysensitivespin-polarizedcurrentswitchwhichcouldpavethewaytonovelspin-basedelectronicdevices.DOI:10.1103/PhysRevX.2.031004SubjectAreas:Graphene,Mesosc
5、opics,Spintronics,TopologicalInsulatorsI.INTRODUCTIONspin-orbit(SO)interaction[10,12,15]andischaracterizedbystateswithoppositespinspropagatinginoppositeElectronicpropertiesofgrapheneandtopologicalinsu-directions[Fig.1(a)].latorshavereceivedconsiderableattentiontheselastfewWherea
6、sexamplesofthree-dimensionaltopologicalyears[1,2].Grapheneisatwo-dimensionalcrystalwhoseinsulatorshavebeenfoundtoaboundinnature,two-electronicbandstructureisthatofagaplesssemiconduc-dimensionalsystemsexhibitingtheQSHphasearesofartor,withconductionandvalencebandstouchingeachother
7、0limitedtoHgTe=CdTeheterostructures,whichonlyafewattwoinequivalentpoints,KandK,commonlyreferredtoexperimentalgroupsintheworldcansynthesize.Itwasasvalleys.Theenergyofchargecarriersvanishesattheserecentlysuggested[16]thatgraphenemightcometothepointsanddisperseslinearlywithmomentum
8、intheirrescue,muchlikeitdidwithtwo-dimensionale
