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.