Piezovalley effect and magnetovalley coupling in altermagnetic semiconductors

TL;DR

This paper investigates the physical mechanisms behind valley polarization in altermagnetic semiconductors, revealing strain-induced effects and magnetovalley coupling that enable potential valleytronic applications at room temperature.

Contribution

It introduces two novel altermagnetic semiconductors and uncovers how strain and spin-orbit coupling induce valley polarization without prior focus on these effects.

Findings

Uniaxial strain induces valley polarization via piezovalley effect without SOC.

Strain transforms ferrovalley semiconductors into semimetals, half metals, or metals.

SOC and magnetocrystalline anisotropy lead to valley polarization through magnetovalley coupling.

Abstract

Clarifying the physical origin of valley polarization and exploring promising ferrovalley materials are conducive to the application of valley degrees of freedom in the field of information storage. Here, we explore two novel altermagnetic semiconductors (monolayers Nb2Se2O and Nb2SeTeO) with N\'eel temperature above room temperature based on first-principles calculations. It reveals that uniaxial strain induces valley polarization without spin-orbital coupling (SOC) in altermagnets owing to the piezovalley effect, while uniaxial compressive strain transforms the intrinsic ferrovalley semiconductor into a semimetal, half metal and metal. Moreover, moderate biaxial strain renders Janus monolayer Nb2SeTeO to robust Dirac-like band dispersion. The SOC and intrinsic in-plane magnetocrystalline anisotropy energy induce Dirac-like altermagnets to generate apparent valley polarization through magnetovalley coupling. In terms of SOC perturbation, we elucidate the physical mechanism behind in-plane-magnetization induced valley polarization and demonstrate the magnitude of valley polarization is positively correlated with the square of SOC strength and negatively correlated with the bandgap. The present work reveals the physical origin of valley polarization in altermagnets and expands the application of ferrovalley at room temperature in valleytronics.