Hot exciton transport in WSe2 monolayers

We experimentally demonstrate hot exciton transport in hexagonal boron nitride encapsulated WSe2 monolayers via spatially and temporally resolved photoluminescence measurements at room temperature. We show that the nonlinear evolution of the mean-squared displacement of the nonresonantly excited hot exciton gas is primarily due to the relaxation of its excess kinetic energy and is characterized by a density-dependent fast expansion that converges to a slower, constant rate expansion. We also observe saturation of the hot exciton gas's expansion rate at high excitation densities due to the balance between Auger-assisted hot exciton generation and the phonon-assisted hot exciton relaxation processes. These measurements provide insight into a process that is ubiquitous in exciton transport measurements where nonresonant optical excitation is typically employed.