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arXiv · 1511.00077

Observation of Valley Zeeman and Quantum Hall Effects at Q Valley of Few-Layer Transition Metal Disulfides

Zefei Wu·Shuigang Xu·Huanhuan Lu·Gui-Bin Liu·Armin Khamoshi·Tianyi Han·Yingying Wu·Jiangxiazi Lin·Gen Long·Yuheng He·Yuan Cai·Fan Zhang·Ning Wang
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Abstract

In few-layer (FL) transition metal dichalcogenides (TMDC), the conduction bands along the Gamma-K directions shift downward energetically in the presence of interlayer interactions, forming six Q valleys related by three-fold rotational symmetry and time reversal symmetry. In even-layers the extra inversion symmetry requires all states to be Kramers degenerate, whereas in odd-layers the intrinsic inversion asymmetry dictates the Q valleys to be spin-valley coupled. In this Letter, we report the transport characterization of prominent Shubnikov-de Hass (SdH) oscillations for the Q valley electrons in FL transition metal disulfide (TMDs), as well as the first quantum Hall effect (QHE) in TMDCs. Our devices exhibit ultrahigh field-effect mobilities (~16,000 cm2V-1s-1 for FL WS2 and ~10,500 cm2V-1s-1 for FL MoS2) at cryogenic temperatures. Universally in the SdH oscillations, we observe a valley Zeeman effect in all odd-layer TMD devices and a spin Zeeman effect in all even-layer TMD devices.

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Zefei Wu, Shuigang Xu, Huanhuan Lu, Gui-Bin Liu, Armin Khamoshi, Tianyi Han, Yingying Wu, Jiangxiazi Lin, Gen Long, Yuheng He, Yuan Cai, Fan Zhang, Ning Wang. 2015-10-31. Observation of Valley Zeeman and Quantum Hall Effects at Q Valley of Few-Layer Transition Metal Disulfides. https://doi.org/10.1038/ncomms12955

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