Valley and spin splittings in a valley layer locked monolayer via atomic adsorption

Abstract

To date, a number of valley materials have been discovered with spin-valley or valley-layer couplings. It is highly desirable to realize the interplay of more electronic degrees of freedom in a valley material. Based on the first-principles calculations, we demonstrate the valley and spin degeneracy liftings in the band structure of a TiSiCO monolayer, with the help of the selective expression of the layer pseudospin via atomic adsorption. The introduction of the transition-metal adatoms provides an effective electric field and magnetic proximity effect, giving rise to considerable valley and spin splittings. The larger valley splitting and the largest spin splitting for the band-edge states have magnitudes of up to 190 meV and 148 meV, respectively. The valley and spin splittings can be further tuned by applying an external electric field. According to the modified band structure, various interlayer excitons with different combinations of spins and electric dipoles are selectively created under the optical field of appropriate frequencies. The tunable spin and valley splittings in atom-adsorbed TiSiCO monolayer offer opportunities for exploring the interactions between spin, valley, and layer pseudospins and designing advanced optoelectronic devices.