Optical generation of excitonic valley coherence in monolayer WSe 2

Aaron M. Jones, Hongyi Yu, Nirmal J. Ghimire, Sanfeng Wu, Grant Aivazian, Jason S. Ross, Bo Zhao, Jiaqiang Yan, David G. Mandrus, Di Xiao, Wang Yao, Xiaodong Xu

Research output: Contribution to journalArticle

820 Scopus citations

Abstract

As a consequence of degeneracies arising from crystal symmetries, it is possible for electron states at band-edges ('valleys') to have additional spin-like quantum numbers. An important question is whether coherent manipulation can be performed on such valley pseudospins, analogous to that implemented using true spin, in the quest for quantum technologies. Here, we show that valley coherence can be generated and detected. Because excitons in a single valley emit circularly polarized photons, linear polarization can only be generated through recombination of an exciton in a coherent superposition of the two valley states. Using monolayer semiconductor WSe 2 devices, we first establish the circularly polarized optical selection rules for addressing individual valley excitons and trions. We then demonstrate coherence between valley excitons through the observation of linearly polarized luminescence, whose orientation coincides with that of the linearly polarized excitation, for any given polarization angle. In contrast, the corresponding photoluminescence from trions is not observed to be linearly polarized, consistent with the expectation that the emitted photon polarization is entangled with valley pseudospin. The ability to address coherence, in addition to valley polarization, is a step forward towards achieving quantum manipulation of the valley index necessary for coherent valleytronics.

Original languageEnglish (US)
Pages (from-to)634-638
Number of pages5
JournalNature Nanotechnology
Volume8
Issue number9
DOIs
StatePublished - Sep 2013
Externally publishedYes

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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  • Cite this

    Jones, A. M., Yu, H., Ghimire, N. J., Wu, S., Aivazian, G., Ross, J. S., Zhao, B., Yan, J., Mandrus, D. G., Xiao, D., Yao, W., & Xu, X. (2013). Optical generation of excitonic valley coherence in monolayer WSe 2. Nature Nanotechnology, 8(9), 634-638. https://doi.org/10.1038/nnano.2013.151