1. Characteristic excitonic absorption of MoSi2N4 and WSi2N4 monolayers.
- Author
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Liu, Hongling, Huang, Baibiao, Dai, Ying, and Wei, Wei
- Subjects
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PERTURBATION theory , *SPIN-orbit interactions , *BAND gaps , *EXCITON theory , *WAVE functions - Abstract
As new members of the two-dimensional materials family, MoSi2N4 and WSi2N4 exhibit unique physical properties. However, their optical properties in consideration of spin–orbit coupling (SOC) have not been discussed. In this work, the excited-state properties of MoSi2N4 and WSi2N4 monolayers are studied by means of many-body perturbation theory in combination with first-principles calculations. We find that the quasiparticle correction leads to a large band gap renormalization of more than 1 eV for MoSi2N4 and WSi2N4 monolayers. Because of the SOC, characteristic A and B excitons form with large binding energies of about 1 eV. The excitation energy difference of A and B excitons can be used to well address the spin–valley splitting. MoSi2N4 shows more abundant excitons (A′, B′ and C excitons), turning out to be a promising candidate to explore intra- and inter-exciton transitions. The exciton wave function indicates that the low-energy excitons in MoSi2N4 and WSi2N4 monolayers are confined in the middle MoN2/WN2 layer, which is unfavorable for excitonic photocatalysis. On the other hand, the valley states based on excitons can be protected by SiN layers from both sides. [ABSTRACT FROM AUTHOR]
- Published
- 2023
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