Drude peak displacement by quantum acoustics

The interaction of electrons with lattice vibration has a central role in numerous phenomena in condensed matter; yet this is often overlooked when regarding the puzzling features of strange and bad metals. Here we unveil the buildup of a displaced Drude peak due to lattice vibration: the optical conductivity exhibits a finite frequency maximum in the far infra-red range while the d.c. conductivity is suppressed. Specifically, our findings shed light on the experimental observations of temperature-dependent electronic absorption peaks in strange/bad metals, where the dynamical lattice disorder steers the system towards non-Drude behavior.