Giant magnetic quantum oscillations in the thermal conductivity of TaAs: Indications of chiral zero sound

TL;DR

This paper reports giant magnetic quantum oscillations in the thermal conductivity of TaAs, suggesting the presence of chiral zero sound as a new heat transport mechanism in topological semimetals.

Contribution

It provides the first observation of giant quantum oscillations in thermal conductivity of a Weyl semimetal and proposes chiral zero sound as an explanation.

Findings

Giant quantum oscillations in thermal conductivity observed in TaAs.

Oscillations are antiphase with electronic density of states.

Conventional heat transport mechanisms cannot explain the phenomena.

Abstract

Charge transport of topological semimetals has been in the focus of intensive investigations because of their non-trivial band topology. Heat transport of these materials, on the other hand, is largely unexplored and remains elusive. Here we report on an observation of unprecedented, giant magnetic quantum oscillations of thermal conductivity in the prototypical Weyl semimetal TaAs. The oscillations are antiphase with the quantum oscillating electronic density of states of a Weyl pocket, and their amplitudes amount to two orders of magnitude of the estimation based on the Wiedemann-Franz law. Our analyses show that all the conventional heat-transport mechanisms through diffusions of propagating electrons, phonons and electron-hole bipolar excitations, are far inadequate to account for these phenomena. Taking further experimental facts that the parallel field configuration favors much higher magneto-thermal conductivity, we propose that the newly proposed chiral zero sound provides a reasonable explanation to these exotic phenomena. More work focusing on other topological semimetals along the same line is badly called for.