Piezoelectric altermagnetism and spin-valley polarization in Janus monolayer $\mathrm{Cr_2SO}$

TL;DR

This paper predicts a novel 2D Janus monolayer $ ext{Cr}_2 ext{SO}$ exhibiting altermagnetism, piezoelectricity, and spin-valley polarization, offering a multifunctional platform for advanced electronic and spintronic devices.

Contribution

It introduces the first prediction of altermagnetic order in $ ext{Cr}_2 ext{SO}$ monolayer with combined piezoelectric and spin-valley properties, expanding 2D material functionalities.

Findings

$ ext{Cr}_2 ext{SO}$ is an altermagnetic semiconductor with spin-split bands.

It exhibits large out-of-plane piezoelectricity ($|d_{31}|=0.97$ pm/V).

Spin and valley polarization can be controlled by uniaxial strain.

Abstract

The altermagnetism can achieve spin-split bands in collinear symmetry-compensated antiferromagnets. Here, we predict altermagnetic order in Janus monolayer $\mathrm{Cr_2SO}$ with eliminated inversion symmetry, which can realize the combination of piezoelectricity and altermagnetism in a two-dimensional material, namely 2D piezoelectric altermagnetism. It is found that $\mathrm{Cr_2SO}$ is an altermagnetic semiconductor, and the spin-split bands of both valence and conduction bands are near the Fermi level. The $\mathrm{Cr_2SO}$ has large out-of-plane piezoelectricity ($|d_{31}|$$=$0.97 pm/V), which is highly desirable for ultrathin piezoelectric device application. Due to spin-valley locking, both spin and valley can be polarized by simply breaking the corresponding crystal symmetry with uniaxial strain. Our findings provide a platform to integrate spin, piezoelectricity and valley in a single material, which is useful for multi-functional device applications.