Non-altermagnetic spin texture in MnTe

TL;DR

This study investigates the spin texture of MnTe, revealing a Rashba-like spin polarization primarily driven by spin-orbit coupling, which challenges the typical altermagnetic behavior and informs future spintronic material design.

Contribution

The paper provides the first direct experimental evidence of a Rashba-like spin texture in MnTe and clarifies the roles of magnetic order and spin-orbit coupling in its spin polarization.

Findings

MnTe exhibits a $k_z$-independent Rashba-like spin texture.

Spin polarization is mainly governed by spin-orbit coupling.

Magnetic order contributes less to spin polarization due to multi-domain effects.

Abstract

Recently, altermagnets have emerged as promising candidates in spintronics, uniquely combining large spin-polarized electronic states with zero net magnetization. A prominent example is $\alpha$-MnTe, whose altermagnetic spin splitting, i.e., the degeneracy lift in momentum space induced by collinear magnetic order, has been experimentally observed. However, the direct evidence of its $g$-wave spin polarization, the key property for altermagnetic spintronics, is thus far lacking. By combining high-resolution spin- and angle-resolved photoemission spectroscopy (SARPES) with first-principles calculations, we reveal a $k_z$-independent, Rashba-like spin texture in $\alpha$-MnTe. Our results indicate that the observed spin polarization is primarily governed by spin-orbit coupling, whereas the magnetic order contributes to the splitting of energy bands but plays a much less dominant role in spin polarization due to the multi-domain nature. From this result, we further establish a way to prescreen altermagnet candidates that favor the formation of large antiferromagnetic domains based on symmetry analysis. Our work elucidates the interplay between magnetic order and spin-orbit coupling in governing spin polarization in altermagnet candidates, and thereby advances the materials design paradigm for spin-functional devices.