Identification of Exciton Complexes in Charge-Tunable Janus WSeS Monolayers

Matthew S.G. Feuer, Alejandro R.P. Montblanch, Mohammed Y. Sayyad, Carola M. Purser, Ying Qin, Evgeny M. Alexeev, Alisson R. Cadore, Barbara L.T. Rosa, James Kerfoot, Elaheh Mostaani, Radosław Kalȩba, Pranvera Kolari, Jan Kopaczek, Kenji Watanabe, Takashi Taniguchi, Andrea C. Ferrari, Dhiren M. Kara, Sefaattin Tongay, Mete Atatüre

Research output: Contribution to journalArticlepeer-review

3 Scopus citations


Janus transition-metal dichalcogenide monolayers are artificial materials, where one plane of chalcogen atoms is replaced by chalcogen atoms of a different type. Theory predicts an in-built out-of-plane electric field, giving rise to long-lived, dipolar excitons, while preserving direct-bandgap optical transitions in a uniform potential landscape. Previous Janus studies had broad photoluminescence (>18 meV) spectra obfuscating their specific excitonic origin. Here, we identify the neutral and the negatively charged inter- and intravalley exciton transitions in Janus WSeS monolayers with ∼6 meV optical line widths. We integrate Janus monolayers into vertical heterostructures, allowing doping control. Magneto-optic measurements indicate that monolayer WSeS has a direct bandgap at the K points. Our results pave the way for applications such as nanoscale sensing, which relies on resolving excitonic energy shifts, and the development of Janus-based optoelectronic devices, which requires charge-state control and integration into vertical heterostructures.

Original languageEnglish (US)
Pages (from-to)7326-7334
Number of pages9
JournalACS nano
Issue number8
StatePublished - Apr 25 2023


  • 2D materials
  • Janus transition-metal dichalcogenides
  • W monolayers
  • charge tunable
  • excitons
  • layered materials

ASJC Scopus subject areas

  • General Materials Science
  • General Engineering
  • General Physics and Astronomy


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