# Low-temperature thermal transport and thermopower of monolayer transition metal dichalcogenide semiconductors

## TL;DR

This paper investigates low-temperature thermal conductivity and thermopower in monolayer transition metal dichalcogenides, linking electronic transport properties to band structure, disorder effects, and external light fields, with implications for thermoelectric applications.

## Contribution

It provides a theoretical framework for understanding thermal transport and thermopower in monolayer TMDCs, including effects of disorder and Floquet engineering, which are novel insights in this material class.

## Key findings

- Thermal conductivity is primarily determined by the band gap at valley edges.
- Disorder reduces thermal conductivity, especially in variable range hopping regimes.
- Valley-resolved thermopower can be achieved under high-frequency light illumination.

## Abstract

We study the low temperature thermal conductivity of single-layer transition metal dichalcogenides. In the low temperature regime where heat is carried primarily through transport of electrons, thermal conductivity is linked to electrical conductivity through the Wiedemann-Franz law. Using a \textit{k.p} Hamiltonian that describes the $ K $ and $ K^{'} $ valley edges, we compute the zero-frequency electric (Drude) conductivity using the Kubo formula to obtain a numerical estimate for the thermal conductivity. The impurity scattering determined transit time of electrons which enters the Drude expression is evaluated within the self-consistent Born approximation. The analytic expressions derived show that low temperature thermal conductivity 1) is determined by the band gap at the valley edges in monolayer TMDCs and 2) in presence of disorder which can give rise to the variable range hopping regime, there is a distinct reduction. Additionally, we compute the Mott thermopower and demonstrate that under a high frequency light beam that sets up a Floquet Hamiltonian, a valley-resolved thermopower can be obtained. A closing summary reviews the implications of results followed by a brief discussion on applicability of the Wiedemann-Franz law and its breakdown in context of the presented calculations.