Multifield Induced Antiferromagnet Transformation into Altermagnet and Realized Anomalous Valley Hall Effect in Two-dimensional Materials

TL;DR

This paper demonstrates how to induce altermagnetism and control valley splitting in two-dimensional materials using external fields, Janus structures, and ferroelectric substrates, revealing new avenues for valley physics and spintronic applications.

Contribution

It introduces a method to realize two-dimensional altermagnetism and manipulate valley splitting via physical fields and ferroelectric polarization, expanding understanding of valley physics.

Findings

Monolayer VPSe3 exhibits valley splitting of 2.91 meV.

Electric fields and Janus structures tune valley splitting magnitude and direction.

Ferroelectric polarization switching can control altermagnetic effects and induce anomalous valley Hall effect.

Abstract

Altermagnetism, as a new category of collinear magnetism distinct from traditional ferromagnetism and antiferromagnetism, exhibits the spin splitting without net magnetization. Currently, researchers are focus on searching three-dimensional altermagnetism and exploring its novel physical properties. However, there is a lack of understanding of the physical origin of two-dimensional altermagnetic emergent behavior. Here, we propose an approach to realize the transition from Neel antiferromagnetism to altermagnetism in two-dimensional system using an electric field, Janus structure, and ferroelectric substrate. In monolayer VPSe3, we demonstrate that multiple-physical-fields cause the upper and lower Se atoms unequal to break PT symmetry, resulting in altermagnetic spin splitting. Noted that monolayer VPSe3 produces a spontaneous valley splitting of 2.91 meV at the conduction band minimum. The electric field can effectively tune the valley splitting magnitude, while the Janus structure not only changes the valley splitting magnitude, but also alters the direction. More interestingly, when the ferroelectric polarization of Al2S3 is upward, the direction of valley polarization is switched and the magnitude is almost unchanged. However, the valley splitting sigfinicantly increases under the downward. It is worth noting that the ferroelectric polarization can switch altermagnetic effect and realize anomalous valley Hall effect. Besides, we reveal the microscopic mechanism of valley splitting by an effective Hamiltonian. Our findings not only provide a method to designing altermagnet, but also enriches the valley physics.