Transverse magnetic heat transport on the topological surface

TL;DR

This paper explores magnetic heat transport on topological insulator surfaces with ferromagnets, deriving formulas for thermal responses, revealing temperature-dependent behaviors, and proposing methods to estimate gaps and Berry phases for controlling thermal currents.

Contribution

It provides new analytical expressions for Nernst and thermal Hall effects on topological surfaces, linking them to temperature, gaps, and Berry phase structures.

Findings

Nernst coefficient and thermal Hall conductivity depend non-monotonously on temperature.

At low temperatures, both effects are linearly proportional to temperature.

Nernst coefficient can be used to estimate the gap induced by time-reversal symmetry breaking.

Abstract

We investigate transverse magnetic heat transport on the surface of a topological insulator on which a ferromagnet is attached. We present general expressions of the Nernst coefficient and the thermal Hall conductivity, which are reduced to simple forms at low temperatures. It is shown that the Nernst coefficient and the thermal Hall conductivity show non-monotonous dependence on temperature. At low temperature, they have linear dependence on temperature. From the behavior of the Nernst coefficient at low temperature, one can estimate the magnitude of the gap induced by time-reversal symmetry breaking. Moreover, we find that the Nernst coefficient can be used to map the Berry phase structure. These results open up possibility to control thermal Hall currents magnetically.