Displaced Drude peak and bad metal from the interaction with slow fluctuations

TL;DR

This paper investigates how slow fluctuations in a metal can cause transient localization of electrons, leading to a displaced Drude peak in optical conductivity and a suppression of d.c. conductivity, revealing a bad metal behavior.

Contribution

It demonstrates how slow bosonic fluctuations induce localization effects and a displaced Drude peak, expanding understanding of bad metal phenomena in correlated electron systems.

Findings

Displaced Drude peak emerges due to slow fluctuation interactions.

Strong interactions enhance electron localization and DDP formation.

Results align with observed DDPs in systems with slow fluctuating degrees of freedom.

Abstract

Scattering by slowly fluctuating degrees of freedom can cause a transient localization of the current-carrying electrons in metals, driving the system away from normal metallic behavior. We illustrate and characterize this general phenomenon by studying how signatures of localization emerge in the optical conductivity of electrons interacting with slow bosonic fluctuations. The buildup of quantum localization corrections manifests itself in the emergence of a displaced Drude peak (DDP), whose existence strongly alters the low frequency optical response and suppresses the d.c. conductivity. We find that for sufficiently strong interactions, many-body renormalization of the fluctuating field induced at metallic densities enhances electron localization and the ensuing DDP phenomenon in comparison with the well-studied low concentration limit. Our results are compatible with the frequent observation of DDPs in electronic systems where slowly fluctuating degrees of freedom couple significantly to the charge carriers.