Abstract
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.
Funder
Shandong Provincial Key Research and Development Program
National Natural Science Foundation of China
Subject
Surfaces, Coatings and Films,Acoustics and Ultrasonics,Condensed Matter Physics,Electronic, Optical and Magnetic Materials
Cited by
2 articles.
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