Strong Rashba effect in the localized impurity states of halogen-doped monolayer PtSe2

The recent epitaxial growth of 1T-phase of PtSe2 monolayer (ML) has opened possibility for its novel applications, in particular for spintronic devices. However, in contrast to 2H-phase of transition-metal dichalcogenides (TMDs), the absence of the spin splitting in the PtSe2 ML may limit the functionality of spintronics. Through fully-relativistic density-functional theory calculations, we show that the large spin splitting can be induced in the PtSe2 ML by introducing a substitutional halogen impurity. Depending on the radius of the halogen dopants, we observe an enhancement of the spin splitting in the localized impurity states (LIS), which is due to the increased contribution of the p-d orbitals coupling. Importantly, we identify very large Rashba splitting in the LIS near Fermi level around the Gamma point characterized by hexagonal warping of the Fermi surface. We further clarify the properties of the Rashba splitting in the LIS by using a simplified Hamiltonian model taking into account the effect of higher order correction of wave vector k. Therefore, this work paves a possible way to induce the significant Rashba splitting in the two-dimensional TMDs, which provide useful information for the potential applications in the spintronic devices operating at room temperature.