Voltage-induced dynamical quantum phase transitions in exciton condensates

We explore nonanalytic quantum phase dynamics of dipolar exciton condensates formed in a system of two-dimensional quantum layers subjected to voltage quenches. We map the exciton condensate physics on to the pseudospin ferromagnet model, showing an additional oscillatory metastable phase beyond the well-known ferromagnetic phase by utilizing a time-dependent, nonperturbative theoretical model. We explain the coherent phase of the exciton condensate in quantum Hall bilayers, observed for currents equal to and slightly larger than the critical current, as a stable time-dependent phase characterized by persistent flow of charged order parameter defect in each of the individual layers with a characteristic ac Josephson frequency. As the magnitude of the voltage quench is further increased, we find that the time-dependent current oscillations associated with the charged order parameter defect flow decay, resulting in a transient pseudospin paramagnet phase characterized by partially coherent charge transfer between layers, before the state relaxes to incoherent charge transfer between the layers.