Abstract
The microscopic theory of a superfluid Fermi liquid at finite temperature is developed for the case of a pure system with -wave pairing, and applied to the calculation of the static properties. As a function of these properties are determined entirely by the Landau parameters , , , etc., characterizing quasiparticle interactions in the normal phase. In particular the spin susceptibility and the density of the normal component are given by where the universal function is the "effective density of states near the Fermi surface" relative to its value in the normal phase. Thus the often-quoted expression is valid for an interacting system only in the limit . In the latter part of the paper a simple phenomenological theory of "Fermi-liquid" effects on and is developed for arbitrary conditions (including the presence of impurities and pairing with ); it is found that under most circumstances explicit expressions for and may be obtained which involve only the Landau parameters and a suitably generalized effective density of states. The theory should apply to the possible superfluid phase of and to most superconductors. It is suggested that the Knight shift in nontransition-metal superconductors should display some "Fermi-liquid" effects. The weak-field dc penetration depth is shown to be insensitive to such effects both in the Pippard limit and near ; however, in a London superconductor at lower temperatures the correction to should be observable and yield a direct estimate of .
- Received 28 June 1965
DOI:https://doi.org/10.1103/PhysRev.140.A1869
©1965 American Physical Society