Direct Observation of Light-dressed States in Monolayer WSe₂ with a Scanning Tunneling Microscope

Engineering quantum materials with light is believed to lead to practical applications in electronic technologies. The monolayer transition metal dichalcogenides (TMD) have emerged as an ideal platform for studies of linear and nonlinear light-matter interactions. However, most studies to date have been performed optically – with light acting as both the perturbation as well as the probe of light-matter interations. In this talk, I will describe the development of an optical-STM designed to perform single-particle tunneling spectroscopy measurements under variable illumination in the near field of an optical fiber. This system allows us to investigate traditional scanning tunneling spectroscopy as a function of optical excitation intensity. We apply this method to monolayers of the transition metal dichalcogenide WSe₂ that are suspended above a gold substrate. We show that at small incident laser powers we observe band shifts, while at large laser power we observe significant renormalization of the effective mass of the valence band.