Quantum-impurity sensing of altermagnetic order

TL;DR

This paper demonstrates that NV-center quantum relaxometry can detect the anisotropic spin dynamics and symmetry-breaking features of altermagnetic insulators through distance and orientation-dependent relaxation measurements.

Contribution

It introduces a novel sensing method to distinguish altermagnets from antiferromagnets by exploiting directional sensitivity of quantum relaxometry.

Findings

Relaxation rate encodes momentum space anisotropy signatures.

Directional sensitivity enables noninvasive distinction of magnetic orders.

NV orientation is crucial for probing anisotropic phenomena.

Abstract

Quantum sensing with individual spin defects has emerged as a versatile platform to probe microscopic properties of condensed matter systems. Here we demonstrate that quantum relaxometry with nitrogen-vacancy (NV) centers in diamond can reveal the anisotropic spin dynamics of altermagnetic insulators together with their characteristic spin polarised bands. We show that the distance and orientation dependent relaxation rate of a nearby quantum impurity encodes signatures of momentum space anisotropy in the spin diffusion response, a hallmark of altermagnetic order. This directional sensitivity is unprecedented in the landscape of quantum materials sensing, and it enables the distinction of altermagnets from conventional antiferromagnets via local, noninvasive measurements. Our results could spark new NV-sensing experiments on spin transport and symmetry breaking in altermagnets, and highlight the role of NV orientation to probe anisotropic phenomena in condensed matter systems.