复旦量子力学2苏汝铿课件chapter2

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1、Chapter2ManyBodyProblem§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