Thermoelectric transport in double-Weyl semimetals

TL;DR

This paper investigates the thermoelectric properties of double-Weyl semimetals, revealing anisotropic transport behavior, magnetic field effects, and the enhancement of chiral anomaly contributions compared to single Weyl nodes.

Contribution

It provides a detailed analysis of thermoelectric transport in double-Weyl systems, including effects of disorder, interactions, and magnetic fields, highlighting unique anisotropic and topological features.

Findings

Transport anisotropy affects relaxation times in different directions.

Magnetic fields influence magnetoconductivity similarly to linear Weyl nodes.

Chiral anomaly contribution doubles with internode scattering compared to single Weyl nodes.

Abstract

We study the thermoelectric properties of a double-Weyl fermion system, possibly realized in $\mathrm{HgCr_2Se_4}$ and $\mathrm{SrSi_2}$, by a semi-classical Boltzmann transport theory. We investigate different relaxation processes including short-range disorder and electron-electron interaction on the thermoelectric transport coefficients. It is found that the anisotropy of the band dispersion for in-plane and out-of-plane momentum directions affects the relaxation time for transport in different directions. The transport also exhibits an interesting directional dependence on the chemical potential and model parameters, differing from a simple isotropic quadratic or linearly dispersing electron gas. By applying a static magnetic field along the linearly dispersing direction, the longitudinal and transverse electrical and thermal magnetoconductivity show a similar dependence on the in-plane cyclotron frequency to the linear dispersing Weyl nodes. By including internode scattering, we find that the chiral anomaly contribution to the thermoelectric coefficients doubles that of a linearly dispersing Weyl node in both the semi-classical and quantum regimes. A magnetic field applied along the quadratically dispersing direction will split the double Weyl point into two single Weyl points with the same chirality.