  The recent epitaxial growth of 1T-phase of PtSe2 monolayer (ML) has opened a
possibility for its novel applications, in particular for spintronics device.
However, in contrast to 2H-phase of transition-metal dichalcogenides (TMDs),
the absence of spin splitting in the PtSe2 ML may limit the functionality for
spintronics application. Through fully-relativistic density-functional theory
calculations, we show that large spin splitting can be induced in the PtSe2 ML
by introducing a substitutional halogen impurity. Depending on the atomic
number (Z) 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. More 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 show that the
Rashba splitting can be controlled by adjusting the doping concentration.
Therefore, this work paves a possible way to induce the significant Rashba
splitting in the two-dimensional TMDs, which is useful for spintronic devices
operating at room temperature.
