Gradient free energy and intrinsic angular momentum in unconventional superconductors

Abstract

We discuss the Ginzburg-Landau gradient-free-energy density for unconventional superconductors. In particular, we consider a certain term related to the intrinsic angular momentum of the Cooper pairs. The coefficient of this term vanishes in weak-coupling theory for a pure metal; as pointed out by Gorkov, it can acquire a nonzero value when impurity scattering is present. We display calculations of this coefficient for both even- and odd-parity gaps using the quasiclassical theory of superconductivity.