The Condensation of Electrons, Holes and Data: Imaging Non-Equilibrium Dynamics at the Microscopic, Mesoscopic, and Statistical Scales
Physical systems driven out of thermal equilibrium may exhibit complex behavior before eventually relaxing to thermal equilibrium. The prototypical non-equilibrium state in quantum materials is the photoexcited electron, where an electron is imparted excess energy and may exhibit a variety of interesting phenomena before eventually recombining with a hole. In nanoscale systems, quantum confinement makes the behavior of non-equilibrium electrons more complex and experimentally accessible. To measure non-equilibrium dynamics, we develop a technique for data-intensively imaging photoresponse that efficiently samples phenomenological parameter space. The result is a large set of images which we condense down to dynamical parameters that can be visualized and physically interpreted. Using this data intensive methodology, we explore the non-equilibrium physics of photoexcited electrons on multiple scales. Firstly, on the microscopic scale we study the interactions of excitons and electron-phonon coupling in TMD heterostructures. Then, zooming out to the mesoscopic scale, we observe an electron-hole liquid phase in MoTe2 and hot carrier regime in graphene heterostructures. Finally, at the statistical scale we explore how a simple model for quieting a noisy antenna can decrease noise in the non-equilibrium states that power photosynthesis. In sum, we demonstrate that data intensive imaging is a powerful and versatile tool for exploring non-equilibrium dynamics of quantum materials and biophysical systems.