苏汝铿高等量子力学讲义ppt课件.ppt

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1、Chapter2ManyBodyProblem§2.1SecondquantizationTheidenticalparticlescannotbedistinguished§2.1SecondquantizationTheessenceoftheidenticalprincipleisthatthestateofasystemshouldbedescribedintermsoftheparticlenumberinacertainquantumstateandthemany-bodyproblemshouldbediscussedintheparticlenumberrepresentat

2、ioninsteadoftheoriginalcoordinaterepresentation§2.1SecondquantizationWeneedtointroducethecreationandtheannihilationoperatorstodealwithvariousprobleminthemany-bodysystem§2.1SecondquantizationBosesystem§2.1Secondquantization§2.1Secondquantization§2.1Secondquantization§2.1Secondquantization§2.1Secondqu

3、antization§2.1Secondquantization§2.1Secondquantization§2.1Secondquantization§2.1Secondquantization§2.1Secondquantization§2.1SecondquantizationDiscussionsThewavefunctionisalreadysymmetricnkistheparticlenumberoperatorofkstate§2.1Secondquantization§2.1Secondquantization§2.1SecondquantizationSecondquant

4、ization§2.1Secondquantization§2.1Secondquantization§2.1Secondquantization§2.1Secondquantization§2.1SecondquantizationForFermions§2.1Secondquantization§2.1Secondquantization§2.1Secondquantization§2.2Hartree-ForkmeanfieldapproximationKey:two-bodyproblem“one-bodyproblem”+“meanfield”Example:Freeelectro

5、ngasinthemetal§2.2Hartree-ForkmeanfieldapproximationScreeningCoulombpotentialPositivechargebackgroundcancelsk=0part§2.2Hartree-Forkmeanfieldapproximation§2.2Hartree-Forkmeanfieldapproximation§2.2Hartree-Forkmeanfieldapproximation§2.2Hartree-Forkmeanfieldapproximation§2.2Hartree-Forkmeanfieldapproxim

6、ation§2.2Hartree-Forkmeanfieldapproximation§2.2Hartree-ForkmeanfieldapproximationSpineffect§2.2Hartree-Forkmeanfieldapproximation§2.2Hartree-Forkmeanfieldapproximation§2.2Hartree-Forkmeanfieldapproximation§2.3SuperconductivetheoryExperimentalresults1908K.OnnesLiquidhelium1911Hg:Tc=4.2K1933Meissneref

7、fectB=01986Muller,BednorzHighTcHeatcapacityCs~exp(-Δ/kBT)Δ~energygapIsotropiceffectTcM^1/2=const.§2.3SuperconductivetheoryFrohlischHamiltonian:e-p-einteractione-eattractionCooperpair:BCSTheory(Variati