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ID:34593174
大小:4.24 MB
页数:81页
时间:2019-03-08
《多分量玻色爱因斯坦凝聚低能动力学的研究》由会员上传分享,免费在线阅读,更多相关内容在学术论文-天天文库。
1、万方数据论了在有效势作用下两种玻色子集体白旋的振动,这一效应有可能在实验上加以观测。关键词:玻色爱因斯坦凝聚元激发低能有效理论万方数据AbstractlIIIItlllllJllttllltlllllllllllllllllllllllllllllY2706019Bose-Einsteincondensationisamacroscopicquantumphenomena.In1924,EinsteingeneralizedBose’Sstatisticaltheoryofelectromagneticradiationtomassiveatoms,andDre
2、dictedthatifthetemperatureofaBosongasWasloweredtoacriticalvalue,thelowestenergystateshouldbemacroscopicallyoccupied,whichgavethenameofBEC.ThiswaSthefirstexampleinhistorythataphasetransitionOccurspurelyduetoquantumeffect,withoutthehelpofinteraction.Duetothetechnicallimitations,BEChasn
3、otbeenobservedforalongtime.In1995.threegroupsinJILA,RiceUniversityandMITcooledacloudofrubidiumatomsto20billionsofakelvinthroughlasercoolingandevaporativecooling,and£orthefirsttimerealizedBECinexperiment,TillnOW,BEChasbeenrealizedexDerimentallyindilutegasesofhydrogen,lithium,sodium,po
4、tassium,rubidiumetc.Therichinternalstructuresofvariousatomsprovidewithpeoplepowerfultoolsforquantumsimulation.Inearlvexperimentstheatomswereconfinedbymagnetictraps,andusuallyonlyatomsoccupyingacertaininternalstatecanbeconfined.Sincetheintroductionofopticaltrap,theinternaldegreesoffre
5、edomarereleasedandthetrappedatomscanoccupydifferentinternalstatessimultaneously,whichcouldbecalledmulticomponentBEC.Sincetheinternalstatesareconventionallydenotedasspincomponents,itcanalsobecalledspinorBEC.ThepurposeofthisthesisistostudythepropertyofamixtureoftwospeciesofspinorBEC,in
6、cludingtwoparts:oneisthemixtureoftwospeciesofpseudospin一1/2atoms,anotheristhemixtureoftwospeciesofspin—latores.Thepaperisorganizedasfollows:^’InChapter1,wefirstgiveabriefintroductionoftheearlyhistoryofBECstudy—ingandtheexperimentaltechniqueoflasercoolingandmagnetic—opticaltrap,thenⅥ,
7、euseGross-Pitaevskiiequationandeffectivefieldtheorytosolvetheelementaryexcitations,finallywediscusstherelationbetweenBECandsuperfluidity.Chapter2describesspinorBEC,mainlythegroundstateandelementaryexcl—tationsoftwocomponentBECandspin-1BEC.Thenwepresentthewayofcon-structinginteraction
8、Hamiltonianf
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