Inducing and Probing Localized Excitons in Atomically Thin Semiconductors via Tip‐Enhanced Cavity‐Spectroscopy

Abstract

Abstract In atomically thin semiconductors, localized exciton (X L ) coupled to light provides a new class of optical sources for potential applications in quantum communication. However, in most studies, X L photoluminescence (PL) from crystal defects has mainly been observed in cryogenic conditions because of their sub‐wavelength emission region and low quantum yield at room temperature. Hybrid‐modality of cavity‐spectroscopy to induce and probe the X L emissions at the nanoscale in atomically thin semiconductors is presented. By placing a WSe 2 monolayer on the two extremely sharp Au tips in a bowtie antenna with a radius of curvature of <1 nm, tensile strain of ≈0.3% is effectively induced in a <30 nm region to create robust X L states. The Au tip then approaches the strained crystal region to enhance the X L emissions and probe them with tip‐enhanced photoluminescence (TEPL) spectroscopy at room temperature. Through this triple‐sharp‐tips cavity‐spectroscopy with <15 nm spatial resolution, TEPL enhancement as high as ≈4.0 × 10 4 by the Purcell effect is achieved, and peak energy shifts of X L up to ≈40 meV are observed. This approach combining nano‐cavity and ‐spectroscopy provides a systematic way to induce and probe the radiative emission of localized excitons in 2D semiconductors offering new strategies for dynamic quantum nano‐optical devices.