Protected valley states and generation of valley- and spin-polarized current in monolayer <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mrow><mml:mi>M</mml:mi><mml:mi>A</mml:mi></mml:mrow><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mi>Z</mml:mi><mml:mn>4</mml:mn></mml:msub></mml:mrow></mml:math>
Jiaren Yuan, Qingyuan Wei, Minglei Sun, Xiaohong Yan, Yongqing Cai, Lei Shen, Udo Schwingenschlögl
Abstract
The optical selection rules obeyed by two-dimensional materials with spin-valley coupling enable the selective excitation of carriers. We show that several members of the monolayer ${MA}_{2}{Z}_{4}$ ($M=\mathrm{Mo}$ and $\phantom{\rule{4pt}{0ex}}W;\phantom{\rule{0.28em}{0ex}}A=\mathrm{C}$, Si, and Ge; $Z=\mathrm{N}$, P, and As) family are direct band-gap semiconductors with protected valley states and that circularly polarized infrared light can induce valley-selective interband transitions. Therefore, they are able to generate a close to 100% valley- and spin-polarized current under an in-plane bias and circularly polarized infrared light, which can be exploited to encode, process, and store information.