Zeeman-like Rashba spin splitting induced persistent spin texture in Janus SiPAs monolayer with strain and electric field effect: an abinitio study

Abstract Spin manipulation without external magnetic fields is essential for next-generation spintronic technologies. In two-dimensional (2D) materials, intrinsic spin–orbit coupling (SOC) can lock spin to momentum, enabling nontrivial spin textures. However, realizing long-lived and symmetry-protected (SP) persistent spin textures (PST) remains challenging. Here, we demonstrate that the Janus SiPAs monolayer intrinsically hosts a Zeeman-like Rashba-induced PST due to its broken inversion and in-plane mirror symmetries, giving rise to a low-symmetry C s point group. This symmetry enforces momentum-independent out-of-plane spin polarization S z near the Y point and X point at the valance band maksimum (VBM), stabilizing a robust PST. At X point in VBM, Zeeman type splitting occurs. Additionally, we find anisotropic Rashba-like spin splitting around the Y point in the VBM. Uniquely, this splitting exhibits pure S z polarization-distinct from conventional Rashba systems-again attributed to the symmetry- constrained spin dynamics of the Janus structure. The coexistence of Zeeman-like and Rashba-like SOC across different Brillouin zone regions results in spin textures that remain locked in the out-of-plane direction. These textures are robust against spin-independent scattering. Finally, we show that uniaxial strain and external electric fields effectively tune Rashba parameters without disrupting symmetry. Our findings establish Janus SiPAs as a promising 2D platform for spintronic devices exploiting SP spin–orbit effects.