Physical Properties Of Fermi Gases With And Without Population Imbalance

Recently,transport properties of condensed matter system have attracted many research efforts in the field of condensed matter physics.Especially,there is widespread interest in the study of the transport and thermodynamic properties of the ultracold Fermi gas since it provides a clean testbed to simulate many complex many-particle systems,which is convenient for the experimental and theoretical study of quantum many-body behavior.By controlling the magnetic field strength,the interaction between the particles can be adjusted,and the system can undergo a continuous crossover from BCS to Bose-Einstein Condensation(BEC).This thesis is organized as follows.In the first part,the connection between the shear viscosity and pressure is studied based on BCS mean-field theory.The expression of the viscosity is rewritten as a form of sum of some observable physical quantities.The behaviors of these quantities are presented in the BCS side,unitary limit and BEC side.In the second part,the homogeneous Fermi gas with tunable population imbalance is studied and the behavior of the shear viscosity is investigated based on the linear response theory consistent with the pairing fluctuation theory.Fermionic contribution and the bosonic degrees of freedom are both considered.The latter is due to the pairing fluctuation effects.The roles of the fermionic and bosonic contributions are addressed in the studies of the shear viscosity of population-imbalanced Fermi gas.The pseudogap clearly makes nontrivial effects to the shear viscosity.