Electronic properties and quasi-particle model of monolayer MoSi$_2$N$_4$

TL;DR

This paper combines first-principles calculations and symmetry analysis to investigate the electronic properties of monolayer MoSi$_2$N$_4$, developing a tight-binding model that describes its low-energy quasi-particle states and plasmon modes.

Contribution

It introduces a three-band tight-binding model for monolayer MoSi$_2$N$_4$ that captures its electronic and plasmonic properties, extending to strained variants and derivatives.

Findings

Spin-orbital coupling causes band splitting.

Horizontal mirror symmetry locks spin polarization along z.

The tight-binding model predicts a $ oot{q}$ plasmon mode.

Abstract

By a combined study with first-principles calculations and symmetry analysis, we theoretically investigate the electronic properties of monolayer MoSi$_2$N$_4$. While the spin-orbital coupling results in bands splitting, the horizontal mirror symmetry locks the spin polarization along z-direction. In addition, a three-band tight-binding model is constructed to describe the low-energy quasi-particle states of monolayer MoSi$_2$N$_4$, which can be generalized to strained MoSi$_2$N$_4$ and its derivatives. The calculations using the tight-binding model show an undamped $\sqrt{q}$-dependent plasmon mode that agrees well with the results of first-principles calculations. Our model can be extended to be suitable for future theoretical and numerical studies of low-energy properties in MoSi$_2$N$_4$ family materials. Furthermore, the study of electronic properties of monolayer MoSi$_2$N$_4$ paves a way for its applications in spintronics and plasmonics.