Ultrafast valley-selective coherent optical manipulation with excitons in WSe2 and MoS2 monolayers

• Published in: NPJ 2D materials and applications Vol. 7; no. 1; pp. 17 - 7
• Main Authors: Slobodeniuk, Artur O., Koutenský, Petr, Bartoš, Miroslav, Trojánek, František, Malý, Petr, Novotný, Tomáš, Kozák, Martin
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 25-03-2023; Nature Publishing Group; Nature Portfolio
• Subjects: 639/624; 639/766/1130; Chalcogenides; Chemistry and Materials Science; Circular polarization; Energy; Excitons; Experiments; Light; Low dimensional semiconductors; Materials Science; Monolayers; Nanotechnology; Physics; Polarized light; Semiconductors; Speed limits; Surfaces and Interfaces; Thin Films; Transition metal compounds; Valleys
• ISSN: 2397-7132; 2397-7132
• DOI: 10.1038/s41699-023-00385-1

Increasing the speed limits of conventional electronics requires innovative approaches to manipulate other quantum properties of electrons besides their charge. An alternative approach utilizes the valley degree of freedom in low-dimensional semiconductors. Here we demonstrate that the valley degeneracy of exciton energies in transition metal dichalcogenide monolayers may be lifted by coherent optical interactions on timescales corresponding to few tens of femtoseconds. The optical Stark and Bloch-Siegert effects generated by strong nonresonant circularly-polarized light induce valley-selective blue shifts of exciton quantum levels by more than 30 meV. We show these phenomena by studying the two most intensive exciton resonances in transiton metal dichalcogenide monolayers and compare the results to a theoretical model, which properly includes the Coulomb interaction and exciton dispersion. These results open the door for ultrafast valleytronics working at multiterahertz frequencies.