Ultrafast laser-driven dynamics in metal/magnetic-insulator interfaces

The nearly free-electron metal next to a localized Mott-insulating state has been recently proposed as a way to probe Kondo lattice physics and to gain insight into how the two extremes of localized and delocalized electron states interact [V. Sunko et al., Sci. Adv. 6, eaaz0611 (2020)]. Although high harmonic generation has been used extensively to investigate the gas phase, its extension to solids is relatively recent, and has not yet been applied to interfaces. Here, we investigate the field-induced dielectric breakdown at the metal/Mott-insulator interface using high harmonic generation, emitted when the interface is subjected to an ultrafast laser pulse. We show that the intensity of high harmonic emission correlates closely with doublon production and the corresponding loss of short-range antiferromagnetic order. For strong interlayer coupling, the harmonic intensity is defined by a phase transition between states that do not exist in a pure Mott-insulator case. For weak interlayer coupling, the threshold for dielectric breakdown is considerably lowered due to the presence of a metallic layer. This suggests that interlayer coupling can be used as an additional knob to control magnetic-insulator breakdown, with implications for using Mott insulators as memristors in neuromorphic circuits.