Synergistic manipulation of valley splitting by sliding ferroelectricity and magnetic proximity effect in Ti-based TMH/MnO/TMH heterostructures

The tunable valley degrees of freedom in van der Waals heterostructures hold great promise for information processing and storage. In this work, we demonstrate that valley splitting can be effectively manipulated by sliding ferroelectricity and the magnetic proximity effect in Ti-based transition metal halide TMH/MnO/TMH heterostructures based on the first-principles calculations. The magnetic proximity coupling between the MnO and TMH layers simultaneously breaks time-reversal and out-of-plane inversion symmetry in the Ti-based transition metal halides layers, inducing valley splitting at the K and K' points. Sliding the MnO layer generates reversible out-of-plane ferroelectricity with a switching barrier of 9.4 meV per unit cell and a switchable polarization of 1.7 × 10−12 C/m. The sliding ferroelectricity and magnetic proximity effect jointly reverse the direction of valley splitting. The difference in electronegativity between surface and interfacial halogen atoms significantly influences the magnitude of the valley splitting, leading to an increase in the conduction band splitting from 9.2 meV for TiClI(Cl) to 19.6 meV for TiClI(I). This work provides an effective approach for controlling valley degrees of freedom via sliding ferroelectricity and the magnetic proximity effect, paving a new pathway for the development of valleytronic and spintronic devices.