A First-principles Study on the Effects of 3d Transition Metal Dopants on the Valleytronic Properties of Janus-type 2H-MoSeTe Monolayers

Valleytronics, a promising field in information technology, utilizes the valley degree of freedom for information storage and processing. Two-dimensional (2D) Janus-type transition metal dichalcogenides (TMDs), such as 2H-MoSeTe, are highly attractive for valleytronics due to their structural asymmetry and significant spin-orbit coupling (SOC). However, the valley splitting in pristine Janus TMDs is limited. Here, we employ first-principles calculations to explore the impact of doping Janus 2H-MoSeTe monolayers with 3d transition metals (Mn, Cr, Fe, Co, Ni) on their valleytronic properties. Our results show that the doped systems exhibit thermodynamic stability and a ferromagnetic ground state with a perpendicular magnetization easy axis. The introduced impurity levels from the dopants’d orbitals hybridize with the host Mo atoms’d orbitals, effectively lifting the K/K′ valley degeneracy. Notably, Mn, Fe, and Cr doping induce significant valley splitting of 141 meV, 119 meV, and 105 meV respectively, underscoring the importance of symmetry breaking and electronic structure changes. The doped systems also display pronounced Berry curvature with opposite signs at the K and K′ valleys, strongly supporting the Anomalous valley Hall effect (AVHE). This work provides a deeper understanding of valleytronics in 2D materials and offers a theoretical foundation for designing next-generation spin-valley-coupled electronic and optoelectronic devices.