Structural, electrical, and Rashba properties of monolayer Janus Si2XY (X,Y =P, As, Sb, and Bi)

In this paper, the structural, electrical, and spin properties of Janus ${\mathrm{Si}}_{2}XY$ ($X,Y=\text{P}$, As, Sb, Bi) structures are studied using first-principles calculations. Elastic constants and phonon dispersion prove that all these structures are stable. The band structures of six compounds are studied and the electrical properties are compared. The charge density has been studied to discover the charge distribution in the conduction and valence bands. These compounds exhibit Rashba spin splitting at the $\mathrm{\ensuremath{\Gamma}}$ and $M$ valleys in the conduction band. Biaxial in-plane strain is used to control the electrical and spin properties. The conduction band minimum can be tuned between the $\mathrm{\ensuremath{\Gamma}}, K$, and $M$ valleys by applying strain. The Rashba spin splitting around the $\mathrm{\ensuremath{\Gamma}}$ and $M$ valleys in the conduction bands of these structures can be improved by strain and have the potential for applications in spintronic devices.