In materials with strong electron-phonon ($e$-ph) interactions, the electrons carry a phonon cloud during their motion, forming quasiparticles known as polarons. Predicting charge transport and its temperature dependence in the polaron regime remains an open challenge. Here, we present first-principles calculations of charge transport in a prototypical material with large polarons, SrTiO$_{ 3}$. Using a cumulant diagram-resummation technique that can capture the strong $e$-ph interactions, our calculations can accurately predict the experimental electron mobility in SrTiO$_{ 3}$ between 150$-$300 K. They further reveal that for increasing temperature the charge transport mechanism transitions from band-like conduction, in which the scattering of renormalized quasiparticles is dominant, to a beyond-quasiparticle transport regime governed by incoherent contributions due to the interactions between the electrons and their phonon cloud. Our work reveals long-sought microscopic details of charge transport in SrTiO$_{ 3}$, and provides a broadly applicable method for predicting charge transport in materials with strong $e$-ph interactions and polarons.
Categories: cond-mat.mtrl-sci cond-mat.str-el