Free Fermi Gas

Yu. M. Suhov

M. Howard Lee

The chemical potential of a D-dimensional free Fermi gas at low temperatures has been obtained using some ideas due to Barker and Blankenbechler [J. Math. Phys. 97, 302 (1986); Am. J. Phys. 25, 279 (1957)]. There is an interesting even–odd-dimensional effect in the behavior of the chemical potential, also observed in other properties of a free Fermi gas, such as the susceptibility. For D=2, it is possible to give a closed form expression, thus valid both in the high- and low-temperature regions, probably not possible in any other even or odd dimensions.

K. Yamada

K. Yamada

We will consider the normal state of interacting Fermi particles without any longrange order. The normal state at low temperatures is called the Fermi liquid and is considered to be the system of free quasi-particles that is continuously connected with free Fermi gas. The concept of the Fermi liquid was introduced and developed by L. D. Landau. Landau's Fermi liquid theory, which concentrates rich contents into a simple theory, is a good example to solve many-body problems. In this chapter, we introduce the basis and main contents of the Fermi liquid. Principle of continuity The basis of the Fermi liquid theory is the principle of adiabatic continuity, which connects free Fermi gas with the Fermi liquid by introducing gradually an interaction among particles. There is a one-to-one correspondence between two states before and after the introduction of the interaction. States belonging to the same symmetry do not cross each other, and new states with the interaction can be represented by the old quantum number. Since the distribution of free Fermi gas is given by the Fermi distribution function n( k ) , that of the Fermi liquid is also written n ( k ). The state denoted by k , σ in the Fermi liquid is called the quasi-particle. For the system to be described by quasi-particles, the following condition is necessary. Let us consider the basis of the Fermi liquid theory following the explanation of the Landau theory given by Nozières and Anderson.

Hui Liu

The properties of an ideal Fermi gas in finite gravitational field are studied,based on the semiclassical(Thomas-Fermi) approximation.The general analytical expressions of the total energy,Fermi energy,chemical potential and heat capacity are derived.Moreover,the analytical expressions of the chemical potential and heat capacity in the high-and low-temperature approximations are given,and then,the example of electron gas is used to calculate exactly.All these results are compared with those of free Fermi gas and Fermi gas in infinite gravitational field.The effects of finite gravitational field on properties of Fermi gas are discussed.