Polaron Dissociation at the Insulator-to-Metal Transition

TL;DR

This paper models the insulator-to-metal transition in dielectrics by analyzing polaron behavior, showing that strong electron-phonon coupling leads to polaron dissociation rather than delocalization, and presents a phase diagram for this transition.

Contribution

It introduces a model for polaron crystallization and dissociation, providing a phase diagram for the insulator-to-metal transition based on density and coupling strength.

Findings

Polaron dissociation occurs at strong electron-phonon coupling.

Delocalization is prevented if coupling exceeds a critical value.

A phase diagram maps the transition as a function of density and coupling.

Abstract

Considering the long range Coulomb interactions between large polarons in dielectrics, we propose a model for their crystallization when no bipolarons are formed. As the density increases, the melting is examined at $T=OK$. One possibility is the delocalization towards a liquid state of polarons. However, we show that this cannot happen if the electron-phonon coupling is larger than some critical value. The other competing mechanism is the dissociation of the polarons themselves, favored owing to their large mass at strong coupling. Finally, we propose a phase diagram for the insulator-to metal transition as a function of the density and electron-phonon coupling.