Electron-phonon Drag Effect on Thermal Conductivity in Two-dimensional Materials

Electron-phonon drag refers to the momentum exchange between nonequilibrium phonons and electrons, and its effect on electronic transport properties, including the Seebeck coefficient and mobility, has been widely studied. However, a systematic study of the impact of nonequilibrium electrons on thermal transport properties, i.e., how extra momentum flow from nonequilibrium electrons to phonons affects thermal conductivity, is still lacking. In this work, by solving the fully coupled electron and phonon Boltzmann transport equations with ab initio scattering parameters, we capture the nonnegligible effect of electron drag on thermal conductivity in two-dimensional (2D) materials. We find that the electron drag effect can significantly increase thermal conductivity. Our study advances the understanding of the effect of nonequilibrium carriers on thermal transport and gives new insights into the nature of coupled electron-phonon transport in 2D semiconductors. This work is based on research supported by the U.S. Air Force Office of Scientific Research under award number FA9550-22-1-0468 and the National Science Foundation (NSF) under award number CBET-1846927. Y.Q. also acknowledges the support from the Graduate Traineeship Program of the NSF Quantum Foundry via the Q-AMASE-i program under award number DMR-1906325 at the University of California, Santa Barbara (UCSB).