Valley manipulation in 2D multiferroic TiInSe3: Doping-induced valley polarization and stacking-engineered effects

The ability to control spin and valley degrees of freedom in two-dimensional materials offers promising prospects for next-generation electronic and spintronic devices. However, achieving tunable valley polarization and intrinsic anomalous Hall effect (AHE) within a single material system without an external magnetic or optical field remains challenging. Here, we present two complementary mechanisms to realize robust valley polarization control in TiInSe3. In the monolayer, electron doping modifies the magnetic easy axis, inducing spontaneous valley polarization. More importantly, in bilayers with specific stacking configurations, intrinsic interlayer charge transfer breaks inversion symmetry, enabling spontaneous valley polarization and a switchable layer-resolved AHE even in the absence of doping. These findings establish fundamental strategies to manipulate spin and valley degrees of freedom through doping and stacking engineering.