FIP Seminar: Imaging Exciton Transport 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. Wave properties of these particles have profound consequences in their transport. 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 excitons in their natural (quantum) time and length scales, experimental approaches combining spatial and temporal resolutions are necessary.

To address this challenge, my research group has developed the combined use of optical microscopy and ultrafast spectroscopy tools to image transport of 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 environment-assisted quantum exciton transport in perovskite quantum dot superlattices, coherent suppression of exciton-exciton annihilation in molecular aggregates, and quantum phase transition of moiré excitons. These results provide fundamental understandings of how excitons 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.