Ab initio many-body theory of polarons at all couplings*

State-of-the-art ab initio theories to describe polarons in materials currently fall into two separate categories: the weak coupling perturbative methods that describe phonon-induced band structure renormalizations, and the strong coupling adiabatic techniques that capture polaron self-trapping effects. The transition region between these regimes remains unclear. In this talk we present a self-consistent many-body theory of polarons that captures both limits and the intermediate regime within a single unified framework. The connection with previous literature on polaron models will be established, and practical first-principles calculations of the zero-point renormalization of band gaps including polaron localization effects will be presented.