Hydrodynamic theory of thermoelectric transport and negative magnetoresistance in Weyl semimetals

TL;DR

This paper develops a hydrodynamic theory for thermoelectric transport in Weyl semimetals, highlighting the role of anomalies and predicting negative thermal magnetoresistance as an experimental signature.

Contribution

It introduces a relativistic fluid-based hydrodynamic framework for Weyl semimetals that includes axial-gravitational anomalies and long-range Coulomb interactions.

Findings

Conductivity matrix is Onsager reciprocal and positive-semidefinite.

Negative thermal magnetoresistance signals the axial-gravitational anomaly.

Theory applies beyond the hydrodynamic limit.

Abstract

We present a theory of thermoelectric transport in weakly disordered Weyl semimetals where the electron-electron scattering time is faster than the electron-impurity scattering time. Our hydrodynamic theory consists of relativistic fluids at each Weyl node, coupled together by perturbatively small inter-valley scattering, and long-range Coulomb interactions. The conductivity matrix of our theory is Onsager reciprocal and positive-semidefinite. In addition to the usual axial anomaly, we account for the effects of a distinct, axial-gravitational anomaly expected to be present in Weyl semimetals. Negative thermal magnetoresistance is a sharp, experimentally accessible signature of this axial-gravitational anomaly, even beyond the hydrodynamic limit.