Transverse Sound Revisited: A Directional Probe of the A-Phase of $UPt_3$

TL;DR

This study measures transverse ultrasonic attenuation in UPt3 to explore its A-phase, revealing distinct directional properties and providing evidence of different symmetries between its phases, advancing understanding of its unconventional superconductivity.

Contribution

It offers the first direct measurement of directional ultrasonic attenuation in UPt3's A-phase, uncovering its unique properties and symmetry differences from the B-phase.

Findings

Attenuation in the A-phase differs from the B-phase.

Directional dependence reveals quasiparticle momentum distribution.

First evidence of different symmetries between UPt3 phases.

Abstract

We have measured the transverse ultrasonic attenuation, $\alpha_{q\epsilon}$, in a well-characterized single crystal of $UPt_3$ for propagation direction, ${\bf q}$, in the basal plane and polarization, $\epsilon$, in and out of the plane. Unlike previous measurements, the sample was of sufficient purity to exhibit three well-defined phases as a function of temperature and magnetic field. We uncover a functional dependence for the attenuation in the (zero field) high temperature phase (A-phase) which is distinctly different than that in the low temperature (B) phase. Our data provide unique directional information on the quasiparticle momentum distribution in this largely unstudied phase of $UPt_3$ and provide the first direct evidence that the two zero-field phases possess different symmetries.