posted on 2024-01-17, 18:36authored byXiao-jing Dong, Kang Jia, Wei-xiao Ji, Sheng-shi Li, Chang-Wen Zhang
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.