Our research program deals broadly with the experimental elucidation of non-equilibrium electronic and structural dynamics of inorganic, organic, and biological materials with atomic-scale spatial and femtosecond temporal resolutions. To achieve this, we use ultrafast four-dimensional electron microscopy (UEM). With UEM, we bring together the high spatial resolution of transmission electron microscopy with the ultrafast temporal resolution of short-pulsed lasers. We are able to directly visualize, in real-time, a wide variety of phenomena, including how crystal lattices respond to the excitation and relaxation of charge-carriers, the collective and coherent motions of lattices at the unit cell level, the real-space dynamics of nanoscale architectures and the effects of interfacial forces, and the effects of charge-transfer reactions on structure. Our group is highly interdisciplinary and collaborative, and our interests are broad, having foundations in materials science and engineering, chemistry, and physics. Our current interests are in three related but distinct areas: (1) energy transport and conversion in defect-laden materials, (2) structural dynamics, phase transitions, and energy transport properties of strongly-correlated materials, and (3) in situ TEM of laser-induced phase transformations and magnetic switching phenomena. The unifying goal of our work is to understand how atomic structure and dynamics lead to the emergence of bulk properties in materials, and how fundamental ultrafast processes of energy coupling occur on the nanoscale.
