Beyond the polaron paradigm: where the real fun begins

Abstract

Solid-state physics textbooks teach us that polarons are rather boring quasi-particles whose effective mass increases if the strength of the coupling to phonons is increased, as does the strength of the effective phonon-mediated attraction between polarons. I will argue that while this view is valid for one class of particle-bosons couplings, there is a second class of physical models with much more interesting behavior. For example, light polarons are possible even at very strong couplings, and depending on circumstances they can experience either a strong phonon-mediated repulsion or a strong attraction of an unusual type.