ABSTRACT
The superfluidity properties have not been as accessible experimentally, but have attracted a great deal of theoretical attention. The properties of Helium as a normal Fermi liquid have been reviewed by G. Baym and C. J. Pethick. The superfluid transition of a Fermi system can be determined by examining the stability of the normal state with respect to the formation of bound states of pairs of quasiparticles with total momentum zero. The transition temperature is determined by a divergence in the scattering amplitude of two quasiparticles at the Fermi surface. Philip W. Anderson and P. Morel gave a correct expression for the superfluid density as normally defined in the weak-coupling, perturbation limit. Almost immediately after the Bardeen-Cooper-SchriefTer (BCS) theory several authors proposed anisotropic generalizations of the BCS phenomena. The anisotropic spin–position correlation leads to a non-zero nuclear spin–spin dipolar interaction, which is vital to the discussion of orientation effects.
