Keldysh space control of charge dynamics in a strongly driven Mott insulator

TL;DR

This study investigates how a Mott insulator's charge dynamics can be controlled using strong optical fields, revealing a transition from multi-photon to tunneling regimes and enabling new out-of-equilibrium phenomena exploration.

Contribution

We demonstrate a method to control charge dynamics in a Mott insulator via Keldysh space tuning, combining ultrafast spectroscopy with electric field variation.

Findings

Observation of coherent bandwidth renormalization

Identification of a Keldysh cross-over in pair production

Control over nonlinear heating processes

Abstract

The fate of a Mott insulator under strong low frequency optical driving conditions is a fundamental problem in quantum many-body dynamics. Using ultrafast broadband optical spectroscopy, we measured the transient electronic structure and charge dynamics of an off-resonantly pumped Mott insulator Ca$_2$RuO$_4$. We observe coherent bandwidth renormalization and nonlinear doublon-holon pair production occurring in rapid succession within a sub-100 femtosecond pump pulse duration. By sweeping the electric field amplitude, we demonstrate continuous bandwidth tuning and a Keldysh cross-over from a multi-photon absorption to quantum tunneling dominated pair production regime. Our results provide a procedure to control coherent and nonlinear heating processes in Mott insulators, facilitating the discovery of novel out-of-equilibrium phenomena in strongly correlated systems.