Valley-selective optical Stark effect of exciton-polaritons in a monolayer semiconductor

Trevor LaMountain; Jovan Nelson; Erik J Lenferink; Samuel H Amsterdam; Akshay A Murthy; Hongfei Zeng; Tobin J Marks; Vinayak P Dravid; Mark C Hersam; Nathaniel P Stern

doi:10.1038/s41467-021-24764-8

Valley-selective optical Stark effect of exciton-polaritons in a monolayer semiconductor

Nat Commun. 2021 Jul 26;12(1):4530. doi: 10.1038/s41467-021-24764-8.

Authors

Trevor LaMountain¹, Jovan Nelson¹, Erik J Lenferink², Samuel H Amsterdam³, Akshay A Murthy^{4

5}, Hongfei Zeng², Tobin J Marks^{3

4}, Vinayak P Dravid^{4

5

6}, Mark C Hersam^{1

3

4

7}, Nathaniel P Stern^{8

9}

Affiliations

¹ Applied Physics Program, Northwestern University, Evanston, IL, 60208, USA.
² Department of Physics and Astronomy, Northwestern University, Evanston, IL, 60208, USA.
³ Department of Chemistry and the Materials Research Center, Northwestern University, Evanston, IL, 60208, USA.
⁴ Department of Materials Science and Engineering and the Materials Research Center, Northwestern University, Evanston, IL, 60208, USA.
⁵ International Institute of Nanotechnology, Northwestern University, Evanston, IL, 60208, USA.
⁶ NUANCE Center, Northwestern University, Evanston, IL, 60208, USA.
⁷ Department of Electrical and Computer Engineering, Northwestern University, Evanston, IL, 60208, USA.
⁸ Applied Physics Program, Northwestern University, Evanston, IL, 60208, USA. n-stern@northwestern.edu.
⁹ Department of Physics and Astronomy, Northwestern University, Evanston, IL, 60208, USA. n-stern@northwestern.edu.

Abstract

Selective breaking of degenerate energy levels is a well-known tool for coherent manipulation of spin states. Though most simply achieved with magnetic fields, polarization-sensitive optical methods provide high-speed alternatives. Exploiting the optical selection rules of transition metal dichalcogenide monolayers, the optical Stark effect allows for ultrafast manipulation of valley-coherent excitons. Compared to excitons in these materials, microcavity exciton-polaritons offer a promising alternative for valley manipulation, with longer lifetimes, enhanced valley coherence, and operation across wider temperature ranges. Here, we show valley-selective control of polariton energies in WS₂ using the optical Stark effect, extending coherent valley manipulation to the hybrid light-matter regime. Ultrafast pump-probe measurements reveal polariton spectra with strong polarization contrast originating from valley-selective energy shifts. This demonstration of valley degeneracy breaking at picosecond timescales establishes a method for coherent control of valley phenomena in exciton-polaritons.

Abstract

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