2016/12/12 by Xiaoxiao Zhang, Xiao-Xiao Zhang, Ting Cao +12 · 449 citations
Engineering · Materials Science · Physics and Astronomy · #2D Materials and Applications #Atomic physics #Biexciton #Condensed matter physics #Exciton #Materials science #Molecular physics #Monolayer #Nanotechnology #Perovskite Materials and Applications #Physics #Quantum Dots Synthesis And Properties #Spin (aerodynamics) #cond-mat.mes-hall
paper · pdf · doi:10.1038/nnano.2017.105
published in Nature Nanotechnology 12(9), 883-888 (Nature Portfolio) · 10 pages, 4 figures
arxiv created 2016/12/12 · openalex publication_date 2017/06/26 · arxiv updated 2017/09/14 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/08
Monolayer transition metal dichalcogenide (TMDC) crystals, as direct-gap materials with unusually strong light-matter interaction, have attracted much recent attention. In contrast to the initial understanding, the minima of the conduction band are predicted to be spin split. Because of this splitting and the spin-polarized character of the valence bands, the lowest-lying excitonic states in WX2 (X=S, Se) are expected to be spin-forbidden and optically dark. To date, however, there has been no direct experimental probe of these dark band-edge excitons, which strongly influence the light emission properties of the material. Here we show how an in-plane magnetic field can brighten the dark excitonic states and allow their properties to be revealed experimentally in monolayer WSe2. In particular, precise energy levels for both the neutral and charged dark excitons were obtained and compared with ab-initio calculations using the GW-BSE approach. Greatly increased emission and valley lifetimes were observed for the brightened dark states as a result of their spin configuration. These studies directly probe the excitonic spin manifold and provide a new route to tune the optical and valley properties of these prototypical two-dimensional semiconductors.