Magnetic brightening and control of dark excitons in monolayer WSe 2

Xiao Xiao Zhang, Ting Cao, Zhengguang Lu, Yu Chuan Lin, Fan Zhang, Ying Wang, Zhiqiang Li, James C. Hone, Joshua A. Robinson, Dmitry Smirnov, Steven G. Louie, Tony F. Heinz

Research output: Contribution to journalArticle

137 Scopus citations

Abstract

Monolayer transition metal dichalcogenide crystals, as direct-gap materials with strong light-matter interactions, have attracted much recent attention. Because of their spin-polarized valence bands and a predicted spin splitting at the conduction band edges, the lowest-lying excitons in WX 2 (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 excitons. Here, we show how an in-plane magnetic field can brighten the dark excitons in monolayer WSe 2 and permit their properties to be observed experimentally. Precise energy levels for both the neutral and charged dark excitons are obtained and compared with ab initio calculations using the GW-BSE approach. As a result of their spin configuration, the brightened dark excitons exhibit much-increased emission and valley lifetimes. These studies directly probe the excitonic spin manifold and reveal the fine spin-splitting at the conduction band edges.

Original languageEnglish (US)
Pages (from-to)883-888
Number of pages6
JournalNature nanotechnology
Volume12
Issue number9
DOIs
StatePublished - Sep 1 2017

All Science Journal Classification (ASJC) codes

  • Bioengineering
  • Atomic and Molecular Physics, and Optics
  • Biomedical Engineering
  • Materials Science(all)
  • Condensed Matter Physics
  • Electrical and Electronic Engineering

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    Zhang, X. X., Cao, T., Lu, Z., Lin, Y. C., Zhang, F., Wang, Y., Li, Z., Hone, J. C., Robinson, J. A., Smirnov, D., Louie, S. G., & Heinz, T. F. (2017). Magnetic brightening and control of dark excitons in monolayer WSe 2. Nature nanotechnology, 12(9), 883-888. https://doi.org/10.1038/nnano.2017.105