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1、Chapter2 ManyBodyProblem§2.1SecondquantizationTheidenticalparticlescannotbedistinguished§2.1SecondquantizationTheessenceoftheidenticalprincipleisthatthestateofasystemshouldbedescribedintermsoftheparticlenumberinacertainquantumstateandthemany-bodyproble
2、mshouldbediscussedintheparticlenumberrepresentationinsteadoftheoriginalcoordinaterepresentation§2.1SecondquantizationWeneedtointroducethecreationandtheannihilationoperatorstodealwithvariousprobleminthemany-bodysystem§2.1SecondquantizationBosesystem§2.1
3、Secondquantization§2.1Secondquantization§2.1Secondquantization§2.1Secondquantization§2.1Secondquantization§2.1Secondquantization§2.1Secondquantization§2.1Secondquantization§2.1Secondquantization§2.1Secondquantization§2.1SecondquantizationDiscussionsThe
4、wavefunctionisalreadysymmetricnkistheparticlenumberoperatorofkstate§2.1Secondquantization§2.1Secondquantization§2.1SecondquantizationSecondquantization§2.1Secondquantization§2.1Secondquantization§2.1Secondquantization§2.1Secondquantization§2.1Secondqua
5、ntizationForFermions§2.1Secondquantization§2.1Secondquantization§2.1Secondquantization§2.2Hartree-ForkmeanfieldapproximationKey:two-bodyproblem?“one-bodyproblem”+“meanfield”Example:Freeelectrongasinthemetal§2.2Hartree-ForkmeanfieldapproximationScreenin
6、gCoulombpotentialPositivechargebackgroundcancelsk=0part§2.2Hartree-Forkmeanfieldapproximation§2.2Hartree-Forkmeanfieldapproximation§2.2Hartree-Forkmeanfieldapproximation§2.2Hartree-Forkmeanfieldapproximation§2.2Hartree-Forkmeanfieldapproximation§2.2Har
7、tree-Forkmeanfieldapproximation§2.2Hartree-ForkmeanfieldapproximationSpineffect§2.2Hartree-Forkmeanfieldapproximation§2.2Hartree-Forkmeanfieldapproximation§2.2Hartree-Forkmeanfieldapproximation§2.3SuperconductivetheoryExperimentalresults1908K.OnnesLiqu
8、idhelium1911Hg:Tc=4.2K1933MeissnereffectB=01986Muller,BednorzHighTcHeatcapacityCs~exp(-Δ/kBT)Δ~energygapIsotropiceffectTcM^1/2=const.§2.3SuperconductivetheoryFrohlischHamiltonian:e-p-einteractione-eattractionCooperpair:BCSTheory(Variati
