Observation of Altermagnetic Spin Splitting in an Intercalated Transition Metal Dichalcogenide

TL;DR

This study experimentally verifies altermagnetic spin splitting in Co1/4TaSe2, a layered compound with high Neel temperature, using ARPES and DFT, revealing temperature-dependent electronic structure changes.

Contribution

First experimental observation of altermagnetic spin splitting in a layered transition metal dichalcogenide with high Neel temperature.

Findings

Confirmed antiferromagnetic order with TN=178 K

Observed altermagnetic spin splitting at the Fermi surface

Detected band structure reconstruction above TN

Abstract

Altermagnetism is a novel magnetic phase combining characteristics of both antiferromagnetism and ferromagnetic ordering. Despite growing theoretical interest in altermagnetic materials, reports of experimentally verified high Neel temperature layered compounds are limited or remain to be firmly established. Here, we present an angle resolved photoemission spectroscopy (ARPES) and density functional theory (DFT) study of Co1/4TaSe2, a compound we identify as a layered altermagnetic material. Magnetic susceptibility measurements confirm type A antiferromagnetic ordering with a Neel temperature of 178 K. Our ARPES measurements reveal an electronic band structure in excellent agreement with DFT calculations, demonstrating clear signatures of altermagnetic spin splitting at the Fermi surface. Furthermore, temperature dependent ARPES reveals a reconstructed valence band structure, with observable band shifts and the closing of energy gaps upon heating above the Neel temperature (TN), consistent with the suppression of altermagnetic order. These findings establish Co1/4TaSe2 as a promising platform for exploring altermagnetic phenomena.