Transient broadband spectroscopy of La₂CuO₄ under sub-gap pumping conditions

Recently, there is growing interest to dynamically control the electronic and magnetic properties of strongly correlated insulating materials using intense off-resonant electromagnetic fields. A necessary first step is to characterize the effects of strong-field absorption on the electronic structure of the material. In this talk , I will present broadband transient reflection spectroscopy results from the insulating cuprate La₂CuO₄ under off-resonant optical pumping conditions. By systematically varying the pump photon energy and fluence, I will show how to differentiate the effects single- and multi-photon absorption processes on the electronic structure. In particular, our results demonstrate that single-photon absorption primarily induces a redshift in the charge-transfer peak, while multi-photon absorption leads to significant broadening of the spectral features. Implications of these results on the prospects for Floquet engineering experiments will be discussed.