Tunning electronic properties of WSe₂/WS₂ Moiré superlattices with light in a scanning tunneling microscope

Moiré superlattices formed by TMD materials have emerged as an ideal platform to study light-matter interaction due to their excellent tunability. In these materials, superlattice potentials can cause interesting confinement effects for excitons and other light-matter hybrids. However, typical far-field optical measurements do not directly probe the spatial phenomena, which exist on a length scale that is well below the diffraction limit. In this talk, I will present our recent study on WSe₂/WS₂ heterostructures with the newly built optical-STM technique which employs an optical fiber probe that allows us to perform single-particle tunneling spectroscopy measurements with near-field laser illumination. We observe spatially dependent photo-induced carrier accumulation in Moiré superlattices as a function of laser intensity. Scanning tunneling spectroscopy under intense laser illumination shows evidence for light-induced band bending with different length scales for electrons and holes. Nano-light is therefore a facile way to achieve local tuning of electronic structure in these 2D semiconductor heterostructures.