Voltage-Driven Breakdown of Electronic Order

The non-thermal breakdown of a Mott insulator has been a topic of great theoretical and experimental interest with technological relevance. Recent experiments have found a sharp non-equilibrium insulator-to-metal transition that is accompanied by hysteresis, a negative differential conductance and lattice deformations. However, a thorough understanding of the underlying breakdown mechanism is still lacking. Here, we examine a scenario in which the breakdown is induced by chemical pressure in a paradigmatic model of interacting spinless fermions on a chain coupled to metallic reservoirs (leads). For the Markovian regime, at infinite bias, we qualitatively reproduce several established results. Beyond infinite bias, we find a rich phase diagram where the nature of the breakdown depends on the coupling strength as the bias voltage is tuned up, yielding different current-carrying non-equilibrium phases. For weak to intermediate coupling, we find a conducting CDW phase with a bias-dependent ordering wave vector. At large interaction strength, the breakdown connects the system to a charge-separated insulating phase. We find instances of hysteretic behavior, sharp current onset and negative differential conductance. Our results can help to shed light on recent experimental findings that address current-induced Mott breakdown.