Current Induced Metal-Insulator Transition in 1D Charge Density Wave

Nakamura, Maeno and co-workers (Scientific Reports, 2013) reported that a modest electric field (∼40 V/cm) suppresses the metal insulator transition in Ca_2-xSr_xRuO₄, so that the metallic phase persists down to temperatures well below the equilibrium transition temperature. They further argued that this effect is an intrinsic nonequilibrium correlation effect, due neither to Joule heating nor filamentary conduction. We investigate theoretically this issue by analysing the case of a 1D charge density wave model, using a Hartree-Fock/Boltzmann equation formalism which includes intraband and interband (up to quadratic order) relaxation processes. We find that even modest fields for which Zener tunnelling is negligible can have a strong effect on the distribution function, increasing the number of carriers in the conduction band and thereby, reducing the gap and ultimately driving a transition from insulating to metal phase. A phase diagram is derived and analysed.