Field-driven Mott gap collapse and resistive switch in correlated insulators

Abstract

Mott insulators can be portrayed as "unsuccessful metals": systems in which a strong Coulomb repulsion prevents charge conduction notwithstanding the metal-like density of conduction electrons. The possibility to unlock such large density of frozen carriers with an electric field offers a tantalizing opportunity to realize new Mott-based microelectronic devices. Here we explicitly unveil how such unlocking happens by solving a simple, yet generic, model for correlated insulators using dynamical mean-field theory. Specifically, we show that the electric breakdown of a Mott insulator can occur via a first-order insulator-to-metal transition, characterized by an abrupt gap-collapse in sharp contrast to the Zener tunneling mechanism. The switch-on of charge conduction is due to the energetic stabilization of a metallic phase that preexists as metastable state in equilibrium and is disconnected from the stable insulator. Our findings rationalize recent experimental observations and offer a guideline for future technological research.