CommensurateSpinDynamicsintheSuperconductingStateofaNCCOsuperconductorHTS高温超导VOLUME90,NUMBER13PHYSICALREVIEWLETTERSweekending4APRIL2021CommensurateSpinDynamicsintheSuperconductingStateofanElectron-DopedCuprateSuperconductorK.Yamada,1,*K.Kurahashi,2,T.Uefuji,1M.Fujita,1S.Park,3,4S.-H.Lee,3andY.Endoh5InstituteforChemicalResearch,KyotoUniversity,Uji611-0011,JapanDepartmentofPhysics,TohokuUniversity,AramakiAoba,Sendai980-8577,Japan3NISTCenterforNeutronResearch,NationalInstituteofStandardsandTechnology,Gaithersburg,Maryland20899-86524DepartmentofMaterialsandNuclearEngineering,UniversityofMaryland,CollegePark,Maryland207425InstituteofMaterialsResearch,TohokuUniversity,Sendai980-8577,Japan(Received29October2021;published4April2021)21Wereportneutronscatteringstudiesontwosinglecrystalsamplesoftheelectron-doped(n-type)superconducting(SC)cuprateNd2xCexCuO4(x0:15)withTc18and25K.Unlikethehole-doped(p-type)SCcuprates,whereincommensuratemagneticuctuationscommonlyexist,then-typecuprateshowscommensuratemagneticuctuationsatthetetragonal(1=21=20)reciprocalpointsbothintheSCandinthenormalstate.Aspingapopensupwhenthen-typecupratebecomesSC,asintheoptimallydopedp-typeLa2xSrxCuO4.Thegapenergy,however,increasesgraduallyuptoabout4meVasTdecreasesfromTcto2K,whichcontrastswiththespinpseudogapbehaviorwithaT-independentgapenergyintheSCstateofp-typecuprates.DOI:10.1103/PhysRevLett.90.137004PACSnumbers:74.25.Ha,74.72.JtHigh-Tcsuperconductivityemergeswhenchargecarriers,holes,orelectronsaredopedintoanantiferro-magnetic(AF)Mottinsulator[1–3].Themechanismofthesuperconductivityliesontheircommontwo-dimensionalCuO2planesintowhichthechargecarriersgo.Oneoftheissuesinunderstandingthemechanismisthequestionoftheelectron-holesymmetry.Theelec-tronicstructureoftheoptimallydopedcupratesshowsevidencefortheelectron-holesymmetry[4,5].Theirphasediagramsasafunctionofdoping,however,areasymmetric[6].Forholedoping,antiferromagnetismrapidlyweakensandisreplacedbyaspin-glass-likephasewithcharacteristicsofincommensuratespincorre-lationsandpseudogapintransportmeasurements.Thepseudogaptemperature,T,iswelldenedintheunder-dopedregionanddecreaseswithdoping.Thesystembecomessuperconducting(SC)overawiderangeoftheholeconcentration,x,aroundtheoptimalx0:15.TheSCstatehasincommensuratespincorrelationswithaT-independentspingap.ThenormalstateoftheunderdopedandoptimallydopedSCregionalsoshowsunusualnon-Fermi-liquid(FL)behaviors.Thereisincreasingevidenceforaquantumcriticalpoint(QCP)aroundtheoptimaldopingwhichisresponsiblefortheunusualpropertiesoftheSCandthenormalphase[7–10].Fortheelectron-doped(n-type)cuprates,ontheotherhand,antiferromagnetismsurvivesuntilthesuper-conductivityappearsoveranarrowrangeofxaroundtheoptimalx0:15.Thenormalstateofthen-typecupratesshowsFermi-liquidT2behaviorinresistivityratherthanthelinearbehaviorofthehole-doped(p-type)cuprates.Therefore,investigatingsimilaritiesanddifferencesofthen-typeandp-typecuprateswouldbecrucialtounder-standingphysicsofthehigh-Tcsuperconductivity.Inthispaper,wereportneutronscatteringmeasure-mentsonsinglecrystalsofthen-typeSCcuprateNd2xCexCuO4(NCCO)(x0:15)withTc18and25K.Wehavefoundcommensuratemagneticuctuationsatthetetragonal1=21=20reciprocalpointsintheSCandnormalstates.AspingapopensupwhenthesystembecomesSC,asintheoptimallydopedp-typeLa2xSrxCuO4[11–13].Thegapenergy,however,in-creasesgraduallyupt...