Biexcitonic optical Stark effects in monolayer molybdenum diselenide

Chaw Keong Yong, Jason Horng, Yuxia Shen, Hui Cai, Alex Wang, Chan Shan Yang, Chung Kuan Lin, Shilong Zhao, Kenji Watanabe, Takashi Taniguchi, Sefaattin Tongay, Feng Wang

Research output: Contribution to journalLetterpeer-review

15 Scopus citations

Abstract

Floquet states, where a periodic optical field coherently drives electrons in solids 1–3 , can enable novel quantum states of matter 4–6 . A prominent approach to realize Floquet states is based on the optical Stark effect. Previous studies on the optical Stark effect often treated the excited state in solids as free quasi-particles 3,7–12 . However, exciton–exciton interactions can be sizeably enhanced in low-dimensional systems and may lead to light–matter interactions that are qualitatively different from those in the non-interacting picture. Here we use monolayer molybdenum diselenide (MoSe 2 ) as a model system to demonstrate that the driving optical field can couple a hierarchy of excitonic states, and the many-body inter-valley biexciton state plays a dominant role in the optical Stark effect. Specifically, the exciton–biexciton coupling in monolayer MoSe 2 breaks down the valley selection rules based on the non-interacting exciton picture. The photon-dressed excitonic states exhibit an energy redshift, splitting or blueshift as the driving photon frequency varies below the exciton transition. We determine a binding energy of 21 meV for the inter-valley biexciton and a transition dipole moment of 9.3 debye for the exciton–biexciton transition. Our study reveals the crucial role of many-body effects in coherent light–matter interaction in atomically thin two-dimensional materials.

Original languageEnglish (US)
Pages (from-to)1092-1096
Number of pages5
JournalNature Physics
Volume14
Issue number11
DOIs
StatePublished - Nov 1 2018

ASJC Scopus subject areas

  • Physics and Astronomy(all)

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