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Proceedings Paper

Valley-selective photon-dressed states in transition metal dichalcogenides
Author(s): Trevor LaMountain; Yen-Jung Chen; Teodor K. Stanev; Nathaniel P. Stern
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Paper 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.

Paper Details

Date Published: 22 February 2018
PDF: 8 pages
Proc. SPIE 10530, Ultrafast Phenomena and Nanophotonics XXII, 1053016 (22 February 2018);
Show Author Affiliations
Trevor LaMountain, Northwestern Univ. (United States)
Yen-Jung Chen, Northwestern Univ. (United States)
Teodor K. Stanev, Northwestern Univ. (United States)
Nathaniel P. Stern, Northwestern Univ. (United States)

Published in SPIE Proceedings Vol. 10530:
Ultrafast Phenomena and Nanophotonics XXII
Markus Betz; Abdulhakem Y. Elezzabi, Editor(s)

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