Theoretical evidence of the spin–valley coupling and valley polarization in two-dimensional MoSi2X4 (X = N, P, and As)

Haoqiang Ai; Di Liu; Jiazhong Geng; Shuangpeng Wang; Kin Ho Lo; Hui Pan

doi:10.1039/D0CP05926A

Theoretical evidence of the spin–valley coupling and valley polarization in two-dimensional MoSi₂X₄ (X = N, P, and As)†

Haoqiang Ai,

^a Di Liu,^b Jiazhong Geng,^b Shuangpeng Wang,

^b Kin Ho Lo*^a and Hui Pan

*^bc

Author affiliations

* Corresponding authors

^a Department of Electromechanical Engineering, Faculty of Science and Technology, University of Macau, Macao SAR, P. R. China
E-mail: fstkhl@um.edu.mo

^b Institute of Applied Physics and Materials Engineering, University of Macau, Macao SAR, P. R. China
E-mail: huipan@um.edu.mo

^c Department of Physics and Chemistry, Faculty of Science and Technology, University of Macau, Macao SAR, P. R. China

Abstract

Very recently, the centimeter-scale MoSi₂N₄ monolayer was synthesized experimentally and exhibited a semiconducting nature with high mobility (Hong et al., Science, 2020, 369, 670–674). Here, we show that MoSi₂N₄ and its analogues, MoSi₂P₄ and MoSi₂As₄, are potential two-dimensional (2D) materials for valleytronics based on first-principles calculations. We demonstrate that the intrinsic inversion symmetry breaking and strong spin–orbital coupling lead to the remarkable spin–valley coupling in the inequivalent valleys at K and K′ points, which result in not only the valley-contrasting transport properties, but also the spin and valley coupled optical selection rules. Moreover, the in-plane strain can tune the bandgaps and spin splitting or even induce an indirect-to-direct bandgap transition for promising application in the strain-tunable valleytronics. We find that the valley polarization can be generated by doping magnetic element. Our findings offer theoretical insight into the exotic physical properties of novel MoSi₂N₄-family materials beyond transition metal dichalcogenides.

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DOI: https://doi.org/10.1039/D0CP05926A
Article type: Paper
Submitted: 14 Nov 2020
Accepted: 19 Jan 2021
First published: 21 Jan 2021

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Phys. Chem. Chem. Phys., 2021,23, 3144-3151

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Theoretical evidence of the spin–valley coupling and valley polarization in two-dimensional MoSi₂X₄ (X = N, P, and As)

H. Ai, D. Liu, J. Geng, S. Wang, K. H. Lo and H. Pan, Phys. Chem. Chem. Phys., 2021, 23, 3144 DOI: 10.1039/D0CP05926A

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Physical Chemistry Chemical Physics

Theoretical evidence of the spin–valley coupling and valley polarization in two-dimensional MoSi₂X₄ (X = N, P, and As)†

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Theoretical evidence of the spin–valley coupling and valley polarization in two-dimensional MoSi₂X₄ (X = N, P, and As)

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Physical Chemistry Chemical Physics