Correlated insulator collapse due to quantum avalanche via in-gap ladder states

The significant discrepancy observed between the predicted and experimental switching fields in correlated insulators under a DC electric field far-from-equilibrium necessitates a reevaluation of current microscopic understanding. Here we show that an electron avalanche can occur in the bulk limit of such insulators at arbitrarily small electric field by introducing a generic model of electrons coupled to an inelastic medium of phonons. The quantum avalanche arises by the generation of a ladder of in-gap states, created by a multi-phonon emission process. Hot-phonons in the avalanche trigger a premature and partial collapse of the correlated gap. The phonon spectrum dictates the existence of two-stage versus single-stage switching events which we associate with charge-density-wave and Mott resistive phase transitions, respectively. The behavior of electron and phonon temperatures, as well as the temperature dependence of the threshold fields, demonstrates how a crossover between the thermal and quantum switching scenarios emerges within a unified framework of the quantum avalanche. The microscopic mechanism of the electric-field-driven insulator-metal transition in strongly correlated systems has been debated. Here the authors present a general theory based on a quantum avalanche mediated by the formation of in-gap ladder states from multiple-phonon emission.

Automated summary

The significant difference between predicted and experimental switching fields in correlated insulators under a far-from-equilibrium DC electric field necessitates a reevaluation of current microscopic understanding. The authors introduce a generic model of electrons coupled to an inelastic phononic medium and show that an electron avalanche can occur in the bulk limit of such insulators at arbitrarily small electric field. The quantum avalanche is triggered by the generation of in-gap states through a multi-phonon emission process, leading to a premature and partial collapse of the correlated gap.