Electron Drag Effect on Thermal Conductivity in Two-dimensional Semiconductors

TL;DR

This study investigates how nonequilibrium electrons influence thermal conductivity in 2D semiconductors through the electron drag effect, revealing significant increases at room temperature that differ from 3D materials.

Contribution

It provides a systematic ab initio analysis of electron drag on thermal conductivity in 2D semiconductors, highlighting the dimensionality-dependent effects and underlying physics.

Findings

Electron drag significantly increases thermal conductivity in 2D semiconductors.

Impact of electron drag is negligible in 3D semiconductors.

Differences are due to electron-phonon scattering phase space and phonon contributions.

Abstract

Two-dimensional (2D) materials have shown great potential in applications as transistors, where thermal dissipation becomes crucial because of the increasing energy density. Although thermal conductivity of 2D materials has been extensively studied, interactions between nonequilibrium electrons and phonons, which can be strong when high electric fields and heat current coexist, are not considered. In this work, we systematically study the electron drag effect, where nonequilibrium electrons impart momenta to phonons and influence the thermal conductivity, in 2D semiconductors using ab initio simulations. We find that, at room temperature, electron drag can significantly increase thermal conductivity by decreasing phonon-electron scattering in 2D semiconductors, while its impact in three-dimensional (3D) semiconductors is negligible. We attribute this difference to the large electron-phonon scattering phase space and higher contribution to thermal conductivity by drag-active phonons. Our work elucidates the fundamental physics underlying coupled electron-phonon transport in materials of various dimensionalities.