Multifunctional altermagnet with large out-of-plane piezoelectric response in Janus V2AsBrO monolayer

Altermagnetism has emerged as a third fundamental category of collinear magnetism, characterized by spin splitting in symmetry-compensated collinear antiferromagnets, offering a promising platform for advances in spintronics and condensed matter physics. Here, based on first-principles calculations, we propose an altermagnetic semiconductor, the asymmetric Janus V2AsBrO monolayer, which exhibits a magnetic easy axis favoring the out-of-plane direction and a Néel temperature (TN) significantly exceeding room temperature. The system exhibits a strain-tunable piezovalley effect, generating valley polarization under uniaxial strain. Notably, hole doping under uniaxial strain generates a net magnetization (M) through a piezomagnetic mechanism. Additionally, the broken inversion symmetry endows the monolayer with a substantial out-of-plane piezoelectric coefficient d31 (2.19 pm/V), presenting broad prospects for the development and design of advanced piezoelectric devices. Our findings provide a promising candidate material for the advancement of 2D multifunctional devices in nanoelectronics, spintronics, valleytronics, and piezoelectrics.