Realization of Dual Anomalous Valley Hall Effect in Antiferromagnetic HfN₂/MnPSe₃ Heterostructure

The absence of an anomalous valley Hall (AVH) effect in HfN₂ can be attributed to its protection by the time-inversion (T) symmetry, resulting in a valley degeneracy in K₊/K_– valleys. On the other hand, MnPSe₃ is protected by T and spatial inversion (P) symmetries, which prohibits spin splitting and consequently hinders the achievement of the AVH. Here, by combining model analysis and first-principles calculation, we construct a HfN₂/MnPSe₃ van der Waals (vdW) heterostructure (HTS). In HfN₂/MnPSe₃ HTS, MnPSe₃ generates a magnetic exchange field that breaks the T symmetry of HfN₂, resulting in the generation of an intrinsic spin valley Hall current. The introduction of the HfN₂ layer disrupts the PT symmetry of MnPSe₃, leading to valley spin splitting in K₊/K_– valleys. Without PT symmetry protection, the AVH effect is observed in the MnPSe₃ layer of HfN₂/MnPSe₃ HTS. The valley splitting of the HfN₂ layer and MnPSe₃ layer in HfN₂/MnPSe₃ HTS gives rise to two distinct valleys in K₊/K_– points at the valence band maximum, respectively. Additionally, valley polarization in HfN₂/MnPSe₃ HTS can be flipped simultaneously by reversing the magnetization of the Mn atom. Moreover, HfN₂/MnPSe₃/Sc₂CO₂ ferroelectric HTS has been constructed to achieve precise control of valley-to-nonvalley-electron conversion and semiconductor-to-metal conversion. Our work offers not only an alternative and controllable approach for realizing the spontaneous AVH effect in antiferromagnetic HTS, but also a platform for designing energy-efficient valleytronic devices.