Symmetry-Breaking Phenomena in MnPS 3 /TMDC Heterostructures: Nonrelativistic Spin Splitting, Altermagnetism and Spin-Valley Effects

We explore symmetry-breaking phenomena in MnPS 3 /TMDC (MoS 2, WS 2, MoSe 2, WSe 2 ) heterostructures using first-principles calculations, considering two high-symmetry stacking configurations, S1 and S2, which differ not only by their interfacial registry but also by a 30° twist between the layers. Depending on the stacking geometry, the systems exhibit two distinct types of nonrelativistic spin splitting (NRSS): S2 hosts altermagnetic-like band crossings, while S1 shows global spin splitting characteristic of symmetry-breaking NRSS. Magnetic exchange and anisotropy parameters indicate that the intrinsic magnetic properties of MnPS 3 are largely preserved upon interfacing. The rotation of Mn spins generates valley splitting in the heterostructure conduction band, enabling magnetically controlled valley-selective optical responses in MnPS 3 /TMDC heterostructures. Our results identify MnPS 3 as a symmetry-tunable antiferromagnetic substrate capable of inducing and controlling spin and valley effects in 2D heterostructures without relying on net magnetization or strong SOC, offering a route toward nonvolatile valleytronic functionalities.