Emergence of Rashba splitting and spin-valley properties in Janus MoGeSiP₂As₂ and WGeSiP₂As₂ monolayers

First-principles calculations are performed to study the structural stability and spintronics properties of Janus MoGeSiP₂As₂ and WGeSiP₂As₂ monolayers. The high cohesive energies and the stable phonon modes confirm that both these structures are experimentally accessible. In contrast to pristine MoSi₂P₄, the Janus monolayers demonstrate reduced direct bandgaps and large spin-split states at K/K’. For the monolayered Janus structure, the broken mirror symmetry with respect to the Mo/W-plane gives rise to a potential gradient normal to the basal plane, which causes difference in the work function for the two surfaces. In addition, the spin textures exposed that breaking the mirror symmetry brings Rashba-type spin splitting in the systems which can be increased by using higher atomic spin-orbit coupling. The large valley spin splitting together with the Rashba splitting in these Janus monolayer structures can make a remarkable contribution to semiconductor valleytronics and spintronics.