Valley polarization, Rashba interaction, and weak altermagnetism in inversion-asymmetric MnPS$_\text{3}|$WS$_\text{2}$ van der Waals heterostructures
The deliberate breaking of inversion ($\mathcal{P}$) symmetry in antiferromagnets has recently emerged as an effective means to induce various features, such as the emergence of Berry curvature, spin-valley locking, magnetoelectric coupling, and the transition from conventional antiferromagnetism to altermagnetism. Conversely, in non-magnetic systems, inversion symmetry breaking in the presence of strong spin-orbit interaction (SOI) gives rise to momentum-dependent spin splitting via the Rashba effect, enabling tunable spin polarization through external electric fields. Motivated by recent advances in two-dimensional materials, we perform first-principles calculations based on density functional theory to investigate the van der Waals (vdW) heterostructure formed by a $\mathcal{P}$-symmetric MnPS$_3$ monolayer and a WS$_2$ monolayer. We demonstrate that the interface hosts a rich interplay of emergent phenomena, including an altermagnetic phase, Rashba spin splitting, spin-valley locking, and valley polarization. Our results demonstrate that the heterostructure exhibits semiconducting behavior with a direct band gap of approximately 1.65~eV and a type-I band alignment. Remarkably, the electronic structure and band alignment can be effectively tuned between type-I and type-II regimes via an external electric field and in-plane biaxial strain. Furthermore, field-induced modulation enables strong control over the altermagnetic phase and the valley splitting. These findings establish the proposed vdW heterostructure as a highly tunable platform with significant potential for spintronic and valleytronic applications.