复旦量子力学讲义qmapter2.ppt

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1、Chapter 2Many Body Problem,2.1 Second quantization,The identical particles cannot be distinguished,2.1 Second quantization,The essence of the identical principle is that the state of a system should be described in terms of the particle number in a certain quantum state and the many-body problem sho

2、uld be discussed in the particle number representation instead of the original coordinate representation,2.1 Second quantization,We need to introduce the creation and the annihilation operators to deal with various problem in the many-body system,2.1 Second quantization,Bose system,2.1 Second quanti

3、zation,2.1 Second quantization,2.1 Second quantization,2.1 Second quantization,2.1 Second quantization,2.1 Second quantization,2.1 Second quantization,2.1 Second quantization,2.1 Second quantization,2.1 Second quantization,2.1 Second quantization,DiscussionsThe wave function is already symmetricnk i

4、s the particle number operator of k state,2.1 Second quantization,2.1 Second quantization,2.1 Second quantization,Second quantization,2.1 Second quantization,2.1 Second quantization,2.1 Second quantization,2.1 Second quantization,2.1 Second quantization,For Fermions,2.1 Second quantization,2.1 Secon

5、d quantization,2.1 Second quantization,2.2 Hartree-Fork mean field approximation,Key:two-body problem“one-body problem”+“mean field”Example:Free electron gas in the metal,2.2 Hartree-Fork mean field approximation,Screening Coulomb potential,Positive charge background cancels k=0 part,2.2 Hartree-For

6、k mean field approximation,2.2 Hartree-Fork mean field approximation,2.2 Hartree-Fork mean field approximation,2.2 Hartree-Fork mean field approximation,2.2 Hartree-Fork mean field approximation,2.2 Hartree-Fork mean field approximation,2.2 Hartree-Fork mean field approximation,Spin effect,2.2 Hartr

7、ee-Fork mean field approximation,2.2 Hartree-Fork mean field approximation,2.2 Hartree-Fork mean field approximation,2.3 Superconductive theory,2.3 Superconductive theory,Frohlisch Hamiltonian:e-p-e interaction e-e attractionCooper pair:BCS Theory(Variational method),Variational wave function,2.3 Su

8、perconductive theory,2.3 Superconductive theory,2.3 Superconductive theory,2.3 Superconductive theory,2.3 Superconductive theory,Bogoliubov-Valatin canonical transformation,2.3 Superconductive theory,2.3 Superconductive theory,2.3 Superconductive theory,2.3 Superconductive theory,2.3 Superconductive

9、 theory,Energy gap equation,2.3 Superconductive theory,2.3 Superconductive theory,2.3 Superconductive theory,2.3 Superconductive theory,Stable state,2.4 Landau phase transition theory,Ehrenfest equation,2.4 Landau phase transition theory,2.4 Landau phase transition theory,2.4 Landau phase transition

10、 theory,2.4 Landau phase transition theory,2.4 Landau phase transition theory,Van Laue criticismCan 2nd order phase transition exist?,2.4 Landau phase transition theory,2.4 Landau phase transition theory,2.4 Landau phase transition theory,2.4 Landau phase transition theory,Landau theoryIntroducing“o

11、rder parameter”,2.4 Landau phase transition theory,2.4 Landau phase transition theory,2.4 Landau phase transition theory,2.4 Landau phase transition theory,min,stable max,instalble phase transition point,2.4 Landau phase transition theory,real,stable img,forbidden,A 0,2.4 Landau phase transition the

12、ory,Landau theory Ehrenfest equation,2.4 Landau phase transition theory,2.4 Landau phase transition theory,2.4 Landau phase transition theory,2.4 Landau phase transition theory,2.5 Superfluidity theory,Landau superfluidity theoryNew idea:elementary excitation,2.5 Superfluidity theory,Experiments:Sup

13、erfluidity 10-510-4 cm(0)Mendelson effect-point,2.5 Superfluidity theory,2.5 Superfluidity theory,Landau theory,2.5 Superfluidity theory,2.5 Superfluidity theory,2.5 Superfluidity theory,2.5 Superfluidity theory,2.5 Superfluidity theory,2.5 Superfluidity theory,2.5 Superfluidity theory,2.5 Superflui

14、dity theory,Bogoliubov approximate second-quantization method,2.5 Superfluidity theory,2.5 Superfluidity theory,2.5 Superfluidity theory,2.5 Superfluidity theory,2.5 Superfluidity theory,2.5 Superfluidity theory,2.5 Superfluidity theory,2.5 Superfluidity theory,2.5 Superfluidity theory,2.5 Superfluidity theory,2.5 Superfluidity theory,