Magnetic and Crystal Symmetry Effects on Spin Hall Conductivity in Altermagnets

TL;DR

This paper investigates how magnetic and crystal symmetries influence the spin Hall conductivity in altermagnets, revealing symmetry-driven effects and potential for tuning spin transport in spintronic devices.

Contribution

It provides the first detailed analysis of symmetry effects on USHC in prototypical altermagnets using first-principles calculations.

Findings

RuO₂ shows trivial USHC contributions under tilted geometry.

CrSb and MnTe exhibit robust, symmetry-driven USHC without tilts.

Controlling symmetry via strain or doping can tune USHC in altermagnets.

Abstract

Altermagnets, which reconcile zero net magnetization with pronounced spin splitting, offer fresh opportunities for spin-based functionalities in next-generation electronic and spintronic devices. In this paper, we explore the unconventional spin Hall conductivity (USHC) in three prototypical altermagnets -- RuO$_2$, CrSb, and MnTe -- and elucidate how distinct magnetic and crystal symmetries modulate their spin Hall responses. RuO$_2$ exhibits only trivial USHC contributions under a tilted geometry, demonstrating that symmetry projections alone can induce apparent unconventional elements. In contrast, CrSb and MnTe manifest robust, symmetry-driven USHC without structural tilts, enabled by easy-axis orientations that reduce magnetic symmetry. Through extensive first-principles calculations, we demonstrate the complementary roles of the time-reversal-even and time-reversal-odd components in determining the overall SHC. Our findings indicate that controlling the interplay between crystal and magnetic symmetry -- for instance, by epitaxial strain or doping -- can provide an experimental avenue to tune USHC magnitudes and directions in altermagnets. These results pave the way for the engineering of multifunctional spintronic devices, where enhanced coherence and robust spin transport are realized in zero-net-moment materials with easily tailored spin configurations.