On the gap structure of UPt$_3$: phases A and B

TL;DR

This study investigates the anisotropic gap structure of UPt$_3$'s phases A and B using thermal conduction and sound attenuation, revealing distinct nodal features and providing new insights into their quasiparticle spectra.

Contribution

It provides the first detailed comparison of gap structures in UPt$_3$'s phases A and B through thermal and acoustic measurements.

Findings

Phase B has a line node in the basal plane and a node along the c-axis.

Phase A exhibits a different gap structure from phase B, with directional quasiparticle spectrum information.

First clear evidence of distinct gap structures in the two phases of UPt$_3$.

Abstract

We have used thermal conduction and transverse sound attenuation to probe the anisotropy of the gap structure in two superconducting phases of UPt$_3$. For the low-temperature phase B, transverse sound has in the past provided strong evidence for a line node in the basal plane. Now, from the anisotropy of the thermal conductivity we further establish the presence of a node along the c-axis and provide information on its k-dependence. For the largely unexplored high-temperature phase A, our study of the attenuation for two directions of the polarization yields directional information on the quasiparticle spectrum, and the first clear indication of a different gap structure in the two phases.