Valley modulation in WSe₂/VSe₂heterostructures via phase engineering

Achieving control and application of the valley degrees of freedom in materials such as transition metal chalcogenides (TMDs) is a critical challenge for valleytronics. In this study, we systematically compared and manipulated the spin-valley characteristics of WSe₂/2H(1T)-VSe₂heterostructures using first-principles calculations. The results revealed a limited difference in valley splitting for WSe₂/2H-VSe₂heterostructures, whereas a significant valley modulation was observed in WSe₂/1T-VSe₂heterostructures due to phase-related band hybridization. Further theoretical analyzes showed that this band hybridization originates from work function differences and orbital characteristics. Moreover, strain engineering was employed to regulate the valley splitting in the two representative configurations that possess the largest valley splitting at the valence band maximum for the WSe₂/2H(1T)-VSe₂heterostructures. As applying a vertical strain by decreasing the interfacial distance of 0.5 Å, the valley splitting was significantly enhanced for both configurations, reaching a maximum value of 172.2 meV in WSe₂/1T-VSe₂heterostructures due to the combined effects of an enhanced magnetic proximity effect and band hybridization. In contrast, biaxial strain showed limited capacity to increase the valley splitting in both heterostructures. This work provides valuable insights into the phase engineering of two-dimensional magnetic materials for the manipulation of spin-valley characteristics in TMDs.