Revealing Hund's multiplets in Mott insulators under strong electric fields

We investigate the strong-field dynamics of a paramagnetic two-band Mott insulator using real-time dynamical mean-field theory. A dielectric breakdown occurs due to many-body Landau-Zener tunnelling, with a threshold field determined by the gap. For a large range of fields, however, we predict that the tunnelling currents are small enough to allow the observation of field-induced localization of electrons, which becomes most strikingly evident in atomic-like local spin multiplets determined by the Hund's coupling $J$. This field-induced localization might provide a way of measuring the value of $J$ in correlated materials. It should be observable in transition metal oxides using time-resolved photo-emission spectroscopy or optical measurements in the presence of strong THz field transients.