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The valley degree of freedom, in addition to charge and spin, can be used to process information and to perform logic operations with the advantage of low power consumption and high speed. The effective manipulation of valley degrees of freedom is essential for their practical applications in valleytronics and spintronics. This study investigates effective strategies for the valley manipulation of the WSeTe/CrI3 van der Waals heterojunction with approximate 2% lattice mismatch by the first-principles calculations. The valley degree of freedom in WSeTe can be modulated by the mag-netism of Cr atoms in the substrate via the magnetic proximity effect, including the vertical strain method and the rotation of the magnetic moments of Cr atoms. First-principles calculations were performed by using the VASP software package with the generalized gradient approximation functional in PerdewBurke-Ernzerhof (PBE) form. The spin-orbit coupling was considered when calculating the band structure to investigate the valley properties. The dependence of valley polarization on vertical strain and the magnetic moment direction of the substrate have been systematically analyzed. There are two distinct stacking configurations for the WSeTe/CrI3 het-erojunction with Te/Se atom at the interface, namely Te-stacking and Se-stacking. While single layer of WSeTe does not have valley polarization, the Te-stacking and Se-stacking WSeTe/CrI3 heterojunctions exhibit valley polarizations of 25 meV and 2 meV, respectively, which is under the combined influence of spin-orbit coupling and the proximity effect from the magnetic substrate CrI3, indicating the importance of the stacking configuration. The Te-stacking configuration of the heterojunction has a larger valley polarization due to stronger orbital hybridization between W atoms in WSeTe layer and Cr atoms in CrI3 layer. The application of vertical strain, which ef-fectively tunes the interlayer distance, significantly regulates the valley polarization. Specifically, the valley polarization is increased to 59 meV when the interlayer dis-tance is decreased by 0.5 Å, while it decreases to 10 meV when the interlayer distance is increased by 0.5 Å. Additionally, when the magnetic moment of the CrI3 substrate is rotated by 360°, the valley polarization varies between -25 meV and 25 meV. It reaches maximum when the magnetic moment is aligned along the out-of-plane direc-tion. In conclusion, this study demonstrates that the valley degree of freedom in the WSeTe/CrI3 van der Waals heterojunction can be effectively manipulated by adjusting the interlayer distance through vertical strain and by controlling the magnetic moment direction of the substrate. These findings provide valuable insights into the design and application of valleytronic and spintronic devices based on two-dimensional van der Waals heterostructures.
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Keywords:
- valley /
- heterojunction /
- magnetic proximity /
- first principles
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