@inproceedings{006a797807344c918dee08df3c045883,
title = "Valley-selective photon-dressed states in transition metal dichalcogenides",
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.",
keywords = "2D materials, Kerr rotation, Stark effect, dressed states, exciton-polaritons, valley pseudospin",
author = "Trevor Lamountain and Chen, {Yen Jung} and Stanev, {Teodor K.} and Stern, {Nathaniel P.}",
note = "Funding Information: The research described here has been supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering under Award No. DE-SC0012130 (cavity exciton-polaritons) and the Office of Naval Research under grant number N00014-16-1-3055 (ultrafast valley manipulation). Sample preparation and characterization were partially supported by the National Science Foundations MRSEC program (DMR-1720139) at the Materials Research Center of Northwestern University. This work made use of the EPIC and KECK-II facilities of the NUANCE Center at Northwestern University and the Northwestern University Micro/Nano Fabrication Facility (NUFAB), which have received support from the Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource (NSF ECCS-1542205); the Materials Research Science and Engineering Center (NSF DMR-1720139) at the Materials Research Center; the International Institute for Nanotechnology (IIN); the Keck Foundation; and the State of Illinois, through the IIN. The authors thank H. Bergeron, I. Balla, J. D. Cain, M. C. Hersam, and V. P. Dravid for preparation of CVD-grown materials used in several of the experiments outlined here. Publisher Copyright: {\textcopyright} 2018 COPYRIGHT SPIE. Downloading of the abstract is permitted for personal use only.; Ultrafast Phenomena and Nanophotonics XXII 2018 ; Conference date: 29-01-2018 Through 31-01-2018",
year = "2018",
doi = "10.1117/12.2285666",
language = "English (US)",
series = "Proceedings of SPIE - The International Society for Optical Engineering",
publisher = "SPIE",
editor = "Elezzabi, {Abdulhakem Y.} and Markus Betz",
booktitle = "Ultrafast Phenomena and Nanophotonics XXII",
}