Science Daily March 23, 2021
An international team of researchers (USA – Ames Laboratory, Iowa State University, University of Missouri Research Reactor, Oak Ridge National Laboratory, Harvard University, Canada) discovered that EuIn2As2 has collinear antiferromagnetic order where the magnetic moment direction determines either a topological-crystalline-insulator phase supporting axion electrodynamics or a higher-order-topological-insulator phase with chiral hinge states. They used neutron diffraction, symmetry analysis, and density functional theory results to demonstrate that EuIn2As2 exhibits low-symmetry helical antiferromagnetic order which makes it a stoichiometric magnetic topological-crystalline axion insulator protected by the combination of a 180∘ rotation and time-reversal symmetries: C2×T=2′. Surfaces protected by 2′ are expected to have an exotic gapless Dirac cone which is unpinned to specific crystal momenta. The tunability is also promising for technologies such as high-precision sensors, magnetic storage media, and quantum computers...read more. Open Access TECHNICAL ARTICLE
Details of the broken-helix magnetic order. Credit: Nature Communications volume 12, Article number: 999 (2021)