In atomically thin two-dimensional semiconductors such as transition metal dichalcogenides (TMDs), controlling the density and type of defects promises to be an effective approach for engineering light-matter interactions. We demonstrate that electron-beam irradiation is a simple tool for selectively introducing defect-bound exciton states associated with chalcogen vacancies in TMDs. Our first-principles calculations and time-resolved spectroscopy measurements of monolayer WSe2 reveal that these defect-bound excitons exhibit exceptional optical properties including a recombination lifetime approaching 200 ns and a valley lifetime longer than 1 μs. The ability to engineer the crystal lattice through electron irradiation provides a new approach for tailoring the optical response of TMDs for photonics, quantum optics, and valleytronics applications.
@article{arxiv.1807.03901,
title = {Microsecond Valley Lifetime of Defect-Bound Excitons in Monolayer WSe$_2$},
author = {Galan Moody and Kha Tran and Xiaobo Lu and Travis Autry and James M. Fraser and Richard P. Mirin and Li Yang and Xiaoqin Li and Kevin L. Silverman},
journal= {arXiv preprint arXiv:1807.03901},
year = {2018}
}