Visualizing spin-polarization of an altermagnet KV$_2$Se$_2$O via spin-selective tunneling

TL;DR

This paper provides direct experimental visualization of a metallic d-wave altermagnet KV2Se2O, revealing symmetry-protected spin splitting and opening new avenues for spintronics without net magnetization.

Contribution

First visualization of a metallic d-wave altermagnet using spin-selective tunneling microscopy, linking crystal symmetry, electronic structure, and spin polarization.

Findings

Observation of momentum-dependent spin splitting with d-wave symmetry

KV2Se2O as a tunable platform for studying unconventional magnetism

Potential for symmetry-engineered spintronics without net magnetization

Abstract

Altermagnetism, a recently identified magnetic phase that combines vanishing net magnetization with momentum-dependent spin splitting, challenges the conventional dichotomy between ferromagnets and antiferromagnets. While several candidate materials have been proposed, direct experimental evidence linking crystal symmetry, electronic structure and d-wave spin polarization remains scarce. Here we report the visualization of a metallic d-wave altermagnet in KV2Se2O. Through spin-selective scanning tunneling microscopy powered by a topological insulator tip, we uncover symmetry-protected momentum-dependent spin splitting that follows a characteristic d-wave form factor. Our results establish KV2Se2O as a tunable platform to study the interplay between spin-valley locking, Fermi-surface instability and unconventional magnetism, and open a pathway toward symmetry-engineered spintronics without net magnetization.