Discerning ground state and photoemission-induced spin textures in altermagnetic $\alpha$-MnTe

TL;DR

This paper investigates the spin textures in altermagnetic $ ext{α}$-MnTe using spin- and angle-resolved photoemission spectroscopy, addressing challenges in data interpretation and revealing unique photoemission effects related to the material's magnetic order.

Contribution

It provides new insights into photoemission-induced spin polarization effects and the interpretation of SARPES data in altermagnets, supported by theoretical calculations.

Findings

Identification of photoemission-induced electron polarization effects.

Distinction between ground state spin textures and photoemission process effects.

Observation of unique photoemission selection rules with linearly-polarized light.

Abstract

Recently discovered altermagnets provide a physical realization of an unconventional compensated magnetic phases with a higher partial-wave type of ordering, reminiscent of unconventional superfluid phases. Their stability under normal conditions has sparked significant research interest, spanning fields from spintronics to topological and correlated quantum materials. Spin- and angle-resolved photoemission spectroscopy (SARPES) has great promise to resolve the momentum-dependent spin textures intricately interweaved with the altermagnetic real space spin order. Using the relativistic $d$-wave-like spin polarization on one of the nodal surfaces of the altermagnetic band structure of $\alpha$-MnTe as an example, we here identify and resolve the challenges associated with (S)ARPES studies on altermagnets and offer insights into data interpretation. We focus particularly on the role of photoemission-induced electron polarization and the coupling between light and the N\'eel vector of a magnetic domain. Our findings reveal an extraordinary behaviour of photoemission selection rules while using linearly-polarized light. We observe, and distinguish, polarization of photoelectrons originating from the sample's ground state spin texture, on one hand, and from the photoemission process, on the other hand. Our experimental results are supported by a combination of ab initio band-structure and 1-step photoemission calculations.