Spin–orbit coupling effect on electronic, optical, and thermoelectric properties of Janus Ga2SSe

Abstract

In this paper, we investigate the electronic, optical, and thermoelectric properties of Ga₂SSe monolayer by using density functional theory. Via analysis of the phonon spectrum and ab initio molecular dynamics simulations, Ga₂SSe is confirmed to be stable at room temperature. Our calculations demonstrate that Ga₂SSe exhibits indirect semiconductor characteristics and the spin–orbit coupling (SOC) effect has slightly reduced its band gap. Besides, the band gap of Ga₂SSe depends tightly on the biaxial strain. When the SOC effect is included, small spin–orbit splitting energy of 90 meV has been found in the valence band. However, the spin–orbit splitting energy dramatically changes in the presence of biaxial strain. Ga₂SSe exhibits high optical absorption intensity in the near-ultraviolet region, up to 8.444 × 10⁴ cm⁻¹, which is needed for applications in optoelectronic devices. By using the Boltzmann transport equations, the electronic transport coefficients of Ga₂SSe are comprehensively investigated. Our calculations reveal that Ga₂SSe exhibits a very low lattice thermal conductivity and high figure of merit ZT and we can enhance its ZT by temperature. Our findings provide further insight into the physical properties of Ga₂SSe as well as point to prospects for its application in next-generation high-performance devices.