Gap Symmetry of Superconductivity in UPd2Al3

Abstract

The angle dependent thermal conductivity of the heavy-fermion superconductor UPd${}_2$Al${}_3$ in the vortex state was recently measured by Watanabe et al. Here we analyze this data from two perspectives: universal heat conduction and the angle-dependence. We conclude that the superconducting gap function $\Delta (\mathbf{k})$ in UPd${}_2$Al${}_3$ has horizontal nodes and is given by $\Delta (\mathbf{k})=\Delta \cos (2\chi )$, with $\chi =c{k}_z$.

8 pages, 4 figures, improved figures in replacement