Thermally enhanced Fröhlich coupling in SnSe

Abstract

To gain insight into the peculiar temperature dependence of the thermoelectric material SnSe, we employ many-body perturbation theory and explore the influence of the electron-phonon interaction on its electronic and transport properties. We show that a lattice dynamics characterized by soft highly polar phonons induces a large thermal enhancement of the Fr\"ohlich interaction. We account for these phenomena in ab initio calculations of the photoemission spectrum and electrical conductivity at finite temperature, unraveling the mechanisms behind recent experimental data. Our results reveal a complex interplay between lattice thermal expansion and Fr\"ohlich coupling, providing a rationale for the in silico prediction of transport coefficients of high-performance thermoelectrics.