Valley-selective photon-dressed states in transition metal dichalcogenides

Trevor LaMountain; Yen-Jung Chen; Teodor K. Stanev; Nathaniel P. Stern

doi:10.1117/12.2285666

22 February 2018 Valley-selective photon-dressed states in transition metal dichalcogenides

Trevor LaMountain, Yen-Jung Chen, Teodor K. Stanev, Nathaniel P. Stern

Proceedings Volume 10530, Ultrafast Phenomena and Nanophotonics XXII; 1053016 (2018) https://doi.org/10.1117/12.2285666
Event: SPIE OPTO, 2018, San Francisco, California, United States

Abstract

When electronic excitations in a semiconductor interact with light, the relevant quasiparticles are hybrid lightmatter dressed states, or exciton-polaritons. In monolayer transition metal dichalcogenides, a class of 2D direct bandgap semiconductors, optical excitations selectively populate distinct momentum valleys with correlated spin projection. The combination of this spin-valley locking with photon dressed states can lead to new optical phenomena in these materials. We present spectroscopic measurements of valley-specific exciton-polaritons in monolayer 2D materials in distinct regimes. When a monolayer is embedded in a dielectric microcavity, strong coupling exciton-polaritons are achieved. Cavity-modified dynamics of the dressed states are inferred from emission. Polarization persists up to room temperature in monolayer MoS₂, in contrast with bare material. We also show that distinct regimes of valley-polarized exciton-polaritons can be accessed with microcavity engineering by tuning system parameters such as cavity decay rate and exciton-photon coupling strength. Further, we report results showing that polarization-sensitive ultrafast spectroscopy can enable sensitive measurements of the valley optical Stark shift, a light-induced dressed state energy shift, in monolayer semiconductors such as WSe₂ and MoS₂. These findings demonstrate distinct approaches to manipulating the picosecond dynamics of valleysensitive dressed states in monolayer semiconductors.

Citation Download Citation

Trevor LaMountain, Yen-Jung Chen, Teodor K. Stanev, and Nathaniel P. Stern "Valley-selective photon-dressed states in transition metal dichalcogenides", Proc. SPIE 10530, Ultrafast Phenomena and Nanophotonics XXII, 1053016 (22 February 2018); https://doi.org/10.1117/12.2285666

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