Intrinsic valley Hall transport in atomically thin MoS2.
Zefei Wu1, Benjamin T Zhou2, Xiangbin Cai2
1Department of Physics and the Center for Quantum Materials, the Hong Kong University of Science and Technology, Hong Kong, China. wzefei@connect.ust.hk.
Nature Communications
|February 7, 2019
Summary
Researchers observed intrinsic valley Hall effects in molybdenum disulfide (MoS2) without external manipulation. This breakthrough in topological valleytronics enables electrical control of electron valleys at room temperature.
Area of Science:
- Condensed Matter Physics
- Materials Science
- Quantum Mechanics
Background:
- Electrons in 2D honeycomb lattices have a valley degree of freedom alongside charge and spin.
- Breaking inversion symmetry in these systems can lead to opposite valley Hall effects.
- Previous valley Hall effects required extrinsic methods like substrate coupling or light illumination.
Purpose of the Study:
- To report the first observation of intrinsic valley Hall transport.
- To demonstrate this phenomenon in non-centrosymmetric molybdenum disulfide (MoS2) without external symmetry breaking.
- To explore the potential for electrical control of valley degree of freedom.
Main Methods:
- Investigated monolayer and trilayer MoS2.
- Measured nonlocal resistance and its relationship to local resistance.
- Examined the temperature dependence of the valley Hall effect.
Main Results:
- Observed intrinsic valley Hall transport in non-centrosymmetric MoS2 (monolayer and trilayer).
- Evidence provided by nonlocal resistance scaling cubically with local resistance.
- The effect persists at room temperature with a micron-scale valley diffusion length.
- No valley Hall signal detected in centrosymmetric bilayer MoS2.
Conclusions:
- Elucidated the topological origin of intrinsic valley Hall effects.
- Demonstrated the feasibility of purely electrical control of valley degree of freedom.
- Significant advancement towards topological valleytronics applications.
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