Photodriven Mott Insulating Heterostructures: A Steady-State Study of Impact Ionization Processes

We investigate the photocurrent and spectral features in a simplified modelof a Mott photovoltaic system consisting of a multilayered insulatingheterostructure. The central correlated region is coupled to two metallic leadskept at different chemical potentials. A periodic drive applied to thecorrelated region produces excited doublons and holons across the Mott gapwhich are then separated by a potential gradient, which mimics thepolarization-induced electric field present in oxyde heterostructures. Thenonequilibrium Floquet steady-state is addressed by means of dynamicalmean-field theory and its Floquet extension, while the so-called auxiliarymaster equation approach is employed as impurity solver. We find that impactionization, identified by a kink in the photocurrent as function of the drivingfrequency, becomes significant and is generally favoured by weak, narrow-bandhybridizations to the leads beyond a certain strength of the driving field. Onthe other hand, in the case of a direct coupling to metallic leads with a flatband, we observe a drastic reduction of impact ionization and of thephotocurrent itself.