Berry curvature physics

2D materials, such as gapped graphene, monolayer TMDs and Weyl semimetals, possess interesting Berry curvature effects (a geometric effect of their band structures). We study the optical and transport properties of these materials arisen from the Berry curvature effects. We also explore the valley degree of freedom of electrons in these materials as a new type of information carrier for electronic and optoelectronic devices.

Reviews

Photonics and optoelectronics of two-dimensional semiconductor transition metal dichalcogenides

K. F. Mak and J. Shan, Nature Photon. 10, 216-226 (2016).

Light-valley interactions in 2D semiconductors

K. F. Mak, D. Xiao, and J. Shan, Nature Photon. 12, 451-460 (2018).

Valley dependent optical properties

Control of valley polarization in monolayer MoS₂ by optical helicity

K. F. Mak, K. He, J. Shan, and T.F. Heinz, Nature Nanotech. 7, 494–498 (2012).

Valley- and spin-polarized Landau levels in monolayer WSe₂

Z. Wang, J. Shan, and K. F. Mak, Nature Nanotech. 12, 144–149 (2017).

Valley dependent transport properties

The valley Hall effect in MoS₂ transistors

K. F. Mak, K. L. McGill, J. Park, and P. L. McEuen, Science 344, 1489-1492 (2014).

Electrical control of the valley Hall effect in bilayer MoS₂ transistors

J. Lee, K. F. Mak, and J. Shan, Nature Nanotech. 11, 421-425 (2016).

Valley magnetoelectricity in single-layer MoS₂

J. Lee, Z. Wang, H. Xie, K. F. Mak, and J. Shan, Nature Mater. 16, 887-891 (2017).

Nonlinear anomalous transport

Nonlinear anomalous Hall effect in few-layer WTe₂

K. Kang, T. Li, E. Sohn, J. Shan, and K. F. Mak, Nature Mater. 18, 324-328 (2019).