Nonlinear doublon-holon production and nonthermal dynamics in a strongly driven Mott insulator Ca2RuO4
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 out-of equilibrium doublon-holon and electronic structure dynamics of a Mott insulator Ca2RuO4 upon intense midinfrared sub-gap pump. We observe coherent bandwidth renormalization and nonlinear doublon-holon pair production occurring within the pump pulse duration. By sweeping the off-resonant electric field amplitude, we demonstrate continuous bandwidth tuning and a Keldysh crossover from a multi-photon absorption to quantum tunneling dominated pair production regime, distinguished by their pump field scaling relations and pair distribution functions. 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.