Imaging ExcitonTransport with Ultrafast Microscopy in the Quantum Regime

At the most fundamental level, transport of energy carriers (such as electrons and excitons) in the solid state is determined by their wavefunctions and the interactions with the lattices and the environment.  The key difficulties in probing transport in the quantum regime in real materials lie in the fast (picosecond or shorter) dephasing processes and the nanoscale localization lengths. Thus, to image the motion of charges and excitons in their natural (quantum) time and length scales, experimental approaches combining spatial and temporal resolutions are necessary, which requires a paradigm shift from conventional spectroscopy and microscopy methods.

 

To address this challenge, my research group has developed the combined use of optical microscopy and ultrafast spectroscopy tools to image transport of charge carriers and excitons from the nanoscale to the mesoscale and over a wide range of temperatures. In my talk, I will discuss our recent progress on imaging the hot carrier transport in hybrid perovskites, environment-assisted quantum exciton transport in perovskite quantum dot superlattices, and exciton phase transitions in moiré superlattices of two-dimensional transition metal dichalcogenides. These results provide fundamental understandings of how excitons and charge carriers migrate in materials and how these processes can be manipulated quantum mechanically. The unique ability to measure and control coherent pathways are critical for both solar energy and quantum information applications.