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Large, valley-exclusive Bloch-Siegert shift in monolayer WS2
Edbert J Sie1, Chun Hung Lui2, Yi-Hsien Lee3
1Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
Science (New York, N.Y.)
|March 11, 2017
Summary
Researchers observed a large Bloch-Siegert shift in tungsten disulfide (WS2) monolayer, enabling valley-exclusive control. This breakthrough enhances the valleytronic properties of 2D materials.
Area of Science:
- Condensed Matter Physics
- Materials Science
- Quantum Optics
Background:
- Coherent interaction with off-resonance light shifts atomic and material energy levels.
- Optical Stark shift is dominant, while the Bloch-Siegert shift is less understood in solids.
- Valleytronics in 2D materials offers novel electronic functionalities.
Purpose of the Study:
- To observe and characterize the Bloch-Siegert shift in a solid-state system.
- To demonstrate valley-exclusive control of optical effects in 2D materials.
- To explore enhanced control over valleytronic properties.
Main Methods:
- Utilized monolayer tungsten disulfide (WS2) as the material system.
- Employed infrared optical driving for coherent interaction.
- Controlled light helicity to differentiate optical effects at different valleys.
Main Results:
- Observed an exceptionally large Bloch-Siegert shift in monolayer WS2.
- Achieved valley-exclusive confinement of the Bloch-Siegert and optical Stark shifts.
- Demonstrated opposite selection rules for these shifts at different valleys.
Conclusions:
- The large, valley-exclusive Bloch-Siegert shift provides a new pathway for manipulating valley properties.
- This work paves the way for advanced control in valleytronic devices.
- Monolayer WS2 is a promising platform for studying and utilizing such quantum optical effects.
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