Watching and controlling energy transport in dense materials on nanometer scales

The ability of energy carriers to move within and between atoms and molecules underlies virtually all material function. Understanding and controlling energy flow requires observing it on ultrasmall and ultrafast spatiotemporal scales, where energetic and structural roadblocks dictate the fate of energy carriers. I will describe a new optical ultrafast microscope based on stroboscopic elastic scattering that allows direct visualization of energy carrier transport in 3D with few-nm spatial precision and picosecond temporal resolution. I will demonstrate the wide applicability of the method for watching all forms of energy carriers – free charges, excitons, phonons and ions – move in materials ranging from silicon to conjugated polymers via 2D transition metal dichalcogenides and metal halide perovskites. Beyond quantifying carrier mobilities, our approach directly correlates material resistivities to local morphology, shedding light on how disorder affects transport pathways in 3D.