简介:Ingraphene,conductanceelectronsbehaveasmasslessrelativisticparticlesandobeyananalogueoftheDiracequationintwodimensionswithachiralnature.Forthisreason,theboundingofelectronsingrapheneintheformofgeometriesofquantumdotsisimpossible.Ingaplessgraphene,duetoitsuniqueelectronicbandstructure,thereisaminimalconductivityatDiracpoints,thatis,inthelimitofzerodoping.Thiscreatesaproblemforusingsuchahighlymotivatednewmaterialinelectronicdevices.Oneofthewaystoovercomethisproblemisthecreationofabandgapinthegraphenebandstructure,whichismadebyinversionsymmetrybreaking(symmetryofsublattices).WeinvestigatetheconfinedstatesofthemasslessDiracfermionsinanimpuredgraphenebytheshort-rangeperturbationsfor"localchemicalpotential"and"localgap".Thecalculatedenergyspectrumexhibitsquitedifferentfeatureswithandwithouttheperturbations.Acharacteristicequationforboundstates(BSs)hasbeenobtained.Itissurprisinglyfoundthattherelationbetweentheradialfunctionsofsublatticeswavefunctions,i.e.,f_m~+(r),g_m~+(r),andf_m~-(r),g_m~-(r),canbeestablishedbySO(2)group.
简介:AvirtualTaylorimpactofcellularmaterialsisanalyzedwithawavepropagationtechnique,i.e.theLagrangiananalysismethod,ofwhichthemainadvantageisthatnopre-assumedconstitutiverelationshipisrequired.Timehistoriesofparticlevelocity,localstrain,andstressprofilesarecalculatedtopresentthelocalstress–strainhistorycurves,fromwhichthedynamicstress–strainstatesareobtained.Thepresentresultsrevealthatthedynamic-rigid-plastichardening(D-R-PH)materialmodelintroducedinapreviousstudyofourgroupisingoodagreementwiththedynamicstress–strainstatesunderhighloadingratesobtainedbytheLagrangiananalysismethod.ItdirectlyreflectstheeffectivenessandfeasibilityoftheD-R-PHmaterialmodelforthecellularmaterialsunderhighloadingrates.
简介:Theadsorptionandelectronicpropertiesofisolatedcobaltphthalocyanine(CoPc)moleculeonanultrathinlayerofNaClhavebeeninvestigated.High-resolutionSTMimagesgiveadetailedpictureofthelowestunoccupiedmolecularorbital(LUMO)ofanisolatedCoPc.ItisshownthattheNaClultrathinlayerefficientlydecouplestheinteractionofthemoleculesfromtheunderneathmetalsubstrate,whichmakesitanidealsubstrateforstudyingthepropertiesofsinglemolecules.Moreover,strongdependenceoftheappearanceofthemoleculesonthesamplebiasintheregionofrelativelyhighbias(>3.1V)isascribedtotheimagepotentialstates(IPSs)ofNaCl/Cu(100),whichmayprovideuswithapossiblemethodtofabricatequantumstoragedevices.
简介:Lifetimemeasurementsoflow-lyingexcitedstatesin^87Zrhavebeenperformedviaβ-γcoincidences.The127MeV^32SbeamwasdeliveredfromtheSector-FocusingCyclotron(SFC)oftheHeavyIonResearchFacilityinLanzhou(HIRFL).Theparentnuclei^87Nbwereproducedbythereaction58Ni(32S,2p1n),atabeamenergy127MeVthrougha8umAldegrader.A200ug/cm^2layerof58Nievaporatedontoa200ug/cm^2thickcarbonfoilwasemployedasthetarget.Afterevaporationresidueswereseparatedfromtheprojectilebeamsbythegas-filledrecoilseparatorSHANS[1],thenucleiofinterest87Zrcanbeobtainedwithahigherpurityandthenwereimplantedintoa300umsilicondetector.