Valley-selective optical Stark effect in monolayer WS[subscript 2]
Name
Fu_Valley-selective.pdf
Size
4.26 MB
Format
Adobe PDF
Checksum (MD5)
4b8765b92d5829977637f6ffe7c6aea1
Author(s)
McIver, James
Lee, Yi-Hsien
Fu, Liang
Kong, Jing
Gedik, Nuh
Sie, Edbert Jarvis
Date Issued
December 2014
Journal
Nature Materials
Publisher
Nature Publishing Group
Citation
Sie, Edbert J., James W. McIver, Yi-Hsien Lee, Liang Fu, Jing Kong, and Nuh Gedik. “Valley-Selective Optical Stark Effect in Monolayer WS[subscript 2].” Nat Mater 14, no. 3 (December 15, 2014): 290–294.
Version
Author's final manuscript
Abstract
Breaking space–time symmetries in two-dimensional crystals can markedly influence their macroscopic electronic properties. Monolayer transition metal dichalcogenides (TMDs) are prime examples where the intrinsically broken crystal inversion symmetry permits the generation of valley-selective electron populations, even though the two valleys are energetically degenerate, locked by time-reversal symmetry. Lifting the valley degeneracy in these materials is of great interest because it would allow for valley-specific band engineering and offer additional control in valleytronic applications. Although applying a magnetic field should, in principle, accomplish this task, experiments so far have not shown valley-selective energy level shifts in fields accessible in the laboratory. Here, we show the first direct evidence of lifted valley degeneracy in the monolayer TMD WS[subscript 2]. By applying intense circularly polarized light, which breaks time-reversal symmetry, we demonstrate that the exciton level in each valley can be selectively tuned by as much as 18 meV through the optical Stark effect. These results offer a new way to control the valley degree of freedom, and may provide a means to realize new Floquet topological phases in two-dimensional TMDs.
MIT Department
Massachusetts Institute of Technology. Department of Electrical Engineering and Computer Science
Massachusetts Institute of Technology. Department of Physics
Terms of Use
Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use.
Persistent DSpace Link
DOI of Published Version
https://doi.org/10.1038/nmat4156
