Anomalous Nernst and Thermal Hall Effects in Tilted Weyl Semimetals

TL;DR

This paper investigates the anomalous Nernst and thermal Hall effects in tilted Weyl semimetals, revealing how tilt magnitude and symmetry influence these thermoelectric responses with potential experimental implications.

Contribution

It provides analytic expressions for Nernst and thermal Hall conductivities in tilted Weyl semimetals, highlighting differences between type-I and type-II phases and effects of inversion symmetry breaking.

Findings

Nernst conductivity is finite and Fermi level independent in small tilt (type-I) Weyl semimetals.

In large tilt (type-II) Weyl semimetals, Nernst response depends logarithmically on Fermi energy.

Fermi surface contributions to thermal Hall conductivity are suppressed at half filling in type-II phase.

Abstract

We study the anomalous Nernst and thermal Hall effects in a linearized low-energy model of a tilted Weyl semimetal, with two Weyl nodes separated in momentum space. For inversion symmetric tilt, we give analytic expressions in two opposite limits: for a small tilt, corresponding to a type-I Weyl semimetal, the Nernst conductivity is finite and independent of the Fermi level, while for a large tilt, corresponding to a type-II Weyl semimetal, it acquires a contribution depending logarithmically on the Fermi energy. This result is in a sharp contrast to the nontilted case, where the Nernst response is known to be zero in the linear model. The thermal Hall conductivity similarly acquires Fermi surface contributions, which add to the Fermi level independent, zero tilt result, and is suppressed as one over the tilt parameter at half filling in the Type-II phase. In the case of inversion breaking tilt, with the tilting vector of equal modulus in the two Weyl cones, all Fermi surface contributions to both anomalous responses cancel out, resulting in zero Nernst conductivity. We discuss two possible experimental setups, representing open and closed thermoelectric circuits.