Phase-field model of insulator-to-metal transition in VO2 under an electric field

Abstract

The roles of an electric field and electronic doping in insulator-to-metal transitions are still not well understood. Here we formulated a phase-field model of insulator-to-metal transitions by taking into account both structural and electronic instabilities as well as free electrons and holes in ${\mathrm{VO}}_{2}$, a strongly correlated transition-metal oxide. Our phase-field simulations demonstrate that in a ${\mathrm{VO}}_{2}$ slab under a uniform electric field, an abrupt universal resistive transition occurs inside the supercooling region, in sharp contrast to the conventional Landau-Zener smooth electric breakdown. We also show that hole doping may decouple the structural and electronic phase transitions in ${\mathrm{VO}}_{2}$, leading to a metastable metallic monoclinic phase which could be stabilized through a geometrical confinement and the size effect. This work provides a general mesoscale thermodynamic framework for understanding the influences of electric field, electronic doping, and stress and strain on insulator-to-metal transitions and the corresponding mesoscale domain structure evolution in ${\mathrm{VO}}_{2}$ and related strongly correlated systems.