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1、PHYSICALREVIEWB,VOLUME63,155412Resonanttransmissionthrough®nite-sizedcarbonnanotubes122231DanielOrlikowski,HatemMehrez,JeremyTaylor,,HongGuo,JianWang,andChristopherRoland1DepartmentofPhysics,TheNorthCarolinaStateUniversity,Raleigh,NorthCarolina276952CenterforthePh
2、ysicsofMaterialsandDepartmentofPhysics,McGillUniversity,Montreal,PQCanadaH3A2T83DepartmentofPhysics,TheUniversityofHongKong,PokfulamRoad,HongKong,China~Received26October2000;published28March2001!Wehaveinvestigatedtheoreticallytheconductancethrough®nite-sizedcarbon
3、nanotubescoupledtofea-turelessleadsinthecontextofstandardtight-bindingmodels.Conductiontakesplaceviaresonanttunneling,andtheresultantspectrumofpeaksmaybeunderstoodintermsofthebandstructureofthenanotubes.Speci®cnanotubesdisplaybothon-andoff-resonancebehaviorasafunc
4、tionofnanotubelengthdependinguponwhetherornotthebandscrossatanonzerokvalue.Wehavealsoinvestigatedtheapproachtothein®nitelimitindetail,and,ingeneral,®ndthatthe®nite-sizeeffectscanpersistouttohundredsofnanometers.Sincethemanipulationofnanotubesintodevicesislikelytoi
5、nducedefects,wehaveinvestigatedtheireffectsontheconduction.Theeffectsofbendingandtwobroadclassesofdefects,i.e.,defectintheabsenceand/orpresenceofaddimers,wereconsidered.Ingeneral,thepresenceofdefectsleadsbothtoareductionandshiftingoftheresonantpeaksattheFermilevel
6、.However,inthein®nitelimit,lowconcentrationsofdefectshaveonlyarelativelymodesteffectonthetransportproperties.Finally,wehaveinvestigatedtheeffectsofanexternallyimposedmagnetic®eldorientedperpendiculartothenanotubeaxis.Themagnetic®eldshiftsthelevels,therebyturningon
7、-andoff-resonantdevicesintoeachother.Alloftheeffectsdiscussedherearetestableexperimentally.DOI:10.1103/PhysRevB.63.155412PACSnumber~s!:61.48.1c,72.80.Rj,73.23.Ad,73.61.WpI.INTRODUCTIONnianscoupledtofeaturelessleads,withafocusonthegen-eralanduniversalaspectsofthetr
8、ansmission.ForthemostThereiscurrentlyintenseinterestintheelectronicprop-part,thesedependonlyonthedimensionsandsymmetriesofertiesofcarbonnanotubes.1Carbo
