Universal dielectric response across a continuous metal-insulator transition

TL;DR

This paper demonstrates that the universal dielectric response naturally appears near the quantum critical point of a correlated fermion model during a continuous metal-insulator transition, linking it to many-body orthogonality catastrophe and glassy dynamics.

Contribution

It provides a microscopic understanding of UDR emergence at the quantum critical point in the Falicov-Kimball model using advanced theoretical methods.

Findings

UDR appears in the quantum critical region of the MIT

Link between UDR and many-body orthogonality catastrophe

Correlation with glassy electronic dynamics

Abstract

A wide range of disordered materials, including disordered correlated systems, show "Universal Dielectric Response" (UDR), followed by a superlinear power-law increase in their optical responses over exceptionally broad frequency regimes. While extensively used in various contexts over the years, the microscopics underpinning UDR remains controversial. Here, we investigate the optical response of the simplest model of correlated fermions, Falicov-Kimball model (FKM), across the continuous metal-insulator transition (MIT) and analyze the associated quantum criticality in detail using cluster extension of dynamical mean field theory (CDMFT). Surprisingly, we find that UDR naturally emerges in the quantum critical region associated with the continuous MIT. We tie the emergence of these novel features to a many-body orthogonality catastrophe accompanying the onset of strongly correlated electronic glassy dynamics close to the MIT, providing a microscopic realization of Jonscher's time-honored proposal as well as a rationale for similarities in optical responses between correlated electronic matter and canonical glass formers.