Ultrahigh-Purity Single-Photon Emission from 2D WSe<sub>2</sub> via Effective Suppression of Classical Emission.

Wu, Wenjing; Strasser, Alex; Xiu, Zhongqi; Ngan, Kinfung; Hoang, Thi D; Liu, Song; Shen, Hangzheng; Holtzman, Luke Nemetz et al. · Nano Lett · 2025

basic_science · Level V

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Abstract

Single-photon emitters (SPEs) in two-dimensional WSe<sub>2</sub> offer high extraction efficiency and on-chip compatibility, but achieving high purity remains challenging. We present two strategies to suppress classical emission and enhance purity in WSe<sub>2</sub>-based SPEs. In monolayer WSe<sub>2</sub>, we exploited the presence and absence of valley-spin locking in free and bound excitons, respectively, to achieve purity of 98.3% via polarization control and 99.0% combined with near-resonant excitation. In bilayer WSe<sub>2</sub>, we obtained 97.0% purity without polarization filtering, enabled by the indirect band gap and inversion symmetry. These values represent some of the highest as-measured purities reported for 2D TMD SPEs. Our methods do not require complex fabrication or instrumentation and are supported by first-principles calculations of the vacancy state of Se and spin degeneracy. This work offers practical pathways for realizing high-quality single-photon sources for emerging quantum technologies.