Exposing Altermagnetism through Momentum Density Spectroscopy

TL;DR

This paper proposes using spin-dependent momentum density spectroscopy techniques, like spin-polarised positron annihilation and magnetic Compton scattering, to experimentally identify and confirm altermagnetic materials, providing a new diagnostic approach.

Contribution

It introduces a theoretical framework for using specific momentum density probes to detect altermagnetism and demonstrates their effectiveness on candidate materials.

Findings

Proposed measurable signals for altermagnetism detection.

Confirmed the potential of these probes to diagnose altermagnetic states.

Highlighted the ability to extract spin-resolved Fermi surfaces.

Abstract

Materials which show a strong time-reversal symmetry-breaking response leading to spin-polarization phenomena, in conjunction with antiparallel magnetic alignments producing zero net magnetization, have recently been identified, classified, and been given the name 'altermagnets'. However, measuring and diagnosing possible candidates as altermagnetics still remains a challenge. From the uncertainty of the material being an altermagnet, additional experimental probes are essential to resolve this. Here, we propose using spin-dependent and magnetic momentum density probes such as spin-polarised positron annihilation and revisiting magnetic Compton scattering. By looking at the previously claimed altermagnetic candidates RuO2, CrSb and MnTe, we present theoretical altermagnetic calculations of the experimental quantities measured by these probes. We show that these quantities should produce a measurable signal and unequivocally confirm the altermagnetic state. We also highlight the additional benefits from these probes such as extracting spin-resolved Fermi surfaces which are key for further understanding the nature of the altermagnetic state.