Effects of Fermi Surface Anisotropy on Unconventional Superconductivity in UPt_3

Abstract

We discuss the weak-coupling BCS theory of the heavy fermion superconductor UPt_3, accounting for that system's anisotropic, multisheeted Fermi surface by expanding the order parameter and pair potential in terms of appropriate basis functions of the irreducible representations of the D_6h crystal point group. Within a phenomenological model for the electronic structure of UPt_3 chosen to capture the qualitative features of local density functional calculations and de Haas-van Alphen measurements, we show how Fermi surface anisotropy can favor pairing in certain symmetry classes, and influence the phase diagram of unconventional superconductors. We also calculate the Ginzburg-Landau coefficients, focussing on those coefficients relevant to current theories of the UPt_3 phase diagram.

26 pages, RevTex, 11 PostScript figures, to be published in J. Low Temp. Phys. (Vol. 111, Nos. 1/2, 1998)