ULTRAFAST MID-INFRARED PUMP-OPTICAL PROBE SPECTROSCOPY OF INSLULATING La₂CuO₄

We report some further progress on the excitation of coherent longitudinal acoustic phonons (CLAPs) in the Mott insulator La₂CuO₄ using intense ultrafast mid-infrared laser pulses measured by changes in the reflectivity (at 800 nm) as a function of pump-probe delay. This talk seeks to motivate the possible mechanisms that enable and resolve a below gap CLAP excitation. More generally, we also look toward implementing this coherent population of longitudinal acoustic phonons - a strain wave - as a reporter of low energy dynamics in quantum materials.