Ultrafast nanoscale exciton dynamics via laser-combined scanning tunneling microscopy in atomically thin materials

Abstract Long-term stable excitons, bound pairs of electrons and holes, in van der Waals materials were found to be handled at room temperature, paving the way to develop optoelectronic/photonic devices for future high-speed communication technology. To miniaturize and integrate such functions to achieve highly efficient excitonic devices, understanding and manipulation of exciton dynamics in the nanoscale structures is absolutely essential. Since the spatial resolution of the optical techniques, which have been mainly used in the research of this field, is limited to μm to several tens of nm, the introduction of new technology is strongly desired. Here, we demonstrate a method to probe and visualize neutral excitons using the laser-combined multiprobe scanning tunneling microscopy (STM) system. Ultrafast dynamics of excitons in the nanostructures produced in an in-plane WS₂/WSe₂ heterostructure, such as dynamics in the ps region of many-body effects under high density and spatial variation in the effect of local defects on lifetime, was successfully revealed with a spatial resolution of 1 nm order. This method is expected to accelerate research on exciton dynamics and the development of applications directly based on the experimental results of nanoscale.