Effects of Fermi Surface Anisotropy on Unconventional Superconductivity in UPt_3

TL;DR

This paper investigates how Fermi surface anisotropy affects the pairing symmetry and phase diagram of the heavy fermion superconductor UPt_3 using a weak-coupling BCS framework and phenomenological electronic structure modeling.

Contribution

It introduces a model incorporating Fermi surface anisotropy to explain its influence on pairing symmetry and the phase diagram of UPt_3, advancing understanding of unconventional superconductivity.

Findings

Fermi surface anisotropy favors certain pairing symmetries.

The model captures qualitative features of experimental electronic structure data.

Calculated Ginzburg-Landau coefficients relevant to UPt_3 phase behavior.

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.