First-principle studies on the ferroelectricity and gate-controlled Rashba spin-orbit coupling of d1T-phase transition-metal dichalcogenide monolayers

Abstract

Two-dimensional ferroelectric Rashba semiconductors exhibit extraordinary orbital and spin structures. In this research, through first-principle calculations, we demonstrate the ferroelectricity of d1T-phase (distorted 1T-phase) transition-metal dichalcogenide monolayers and realize the manipulation of the Rashba spin-orbit coupling by means of gate voltage. Because of its large composition of out-of-plane atomic orbitals, the rotation of transition metal atoms induced symmetry breaking leads to larger Rashba spin splittings at Γ point of top valence band (560.4 meV Å for WS 2 , measured by the first derivative of the energy splitting to the wave vector), and it further increases under a vertical downward electric field and hole doping, which correspond to a positive gate voltage for the constructed device. In comparison, charge doping has a greater effect on Rashba parameters than electric field. These results are of great value to the spin-orbit electronics of two-dimensional materials and their applications in electrically controlled spintronics and memory devices. • The ferroelectricity and Rashba SOC of monolayer d1T-phase TMDs are demonstrated. • The Rashba parameter is evaluated by the first derivative of the energy splitting. • One factor of greater Rashba strength is larger vertical orbital composition. • Another origin is the gradient of potential energy affected by charge transfer. • The strength is tuned linearly by electric field and nonlinearly by charge doping.