Topological spin excitations observed in a three-dimensional antiferromagnet

Abstract

Band topology, or global wave-function structure that enforces novel properties in the bulk and on the surface of crystalline materials, is currently under intense investigations for both fundamental interest and its technological promises. While band crossing of non-trivial topological nature was first studied in three dimensions for electrons, the underlying physical idea is not restricted to fermionic excitations. In fact, experiments have confirmed the possibility to have topological band crossing of electromagnetic waves in artificial structures. Fundamental bosonic excitations in real crystals, however, have not been observed to exhibit the counterpart under ambient pressure and magnetic field, where the difficulty is in part because natural materials cannot be precisely engineered like artificial structures. Here, we use inelastic neutron scattering to reveal the presence of topological spin excitations (magnons) in a three-dimensional antiferromagnet, Cu3TeO6, which features a unique lattice of magnetic spin-1/2 Cu2+ ions. Beyond previous understanding, we find that the material's spin lattice possesses a variety of exchange interactions, with the interaction between the ninth-nearest neighbours being as strong as that between the nearest neighbours. Although theoretical analysis indicates that the presence of topological magnon band crossing is independent of model details, Cu3TeO6 turns out to be highly favourable for the experimental observation, as its optical magnons are spectrally sharp and intense due to the highly interconnected spin network and the large magnetic cell. The observed magnon band crossing generally has the form of a special type of Z2-topological nodal lines that are yet to be found in fermion systems, rendering magnon systems a fertile ground for exploring novel band topology.

8 pages, 4 figures, plus methods and supplemental figures. Submitted

References in corpus (34)

• Electronic Structure of Pyrochlore Iridates: From Topological Dirac Metal to Mott Insulator
• Weyl and Dirac Semimetals in Three Dimensional Solids
• Topological Photonics
• Discovery of a Weyl Fermion Semimetal and Topological Fermi Arcs
• Classification of topological quantum matter with symmetries
• Discovery of a Three-dimensional Topological Dirac Semimetal, Na3Bi
• Dirac semimetal in three dimensions
• Topological quantum chemistry
• Colloquium: Topological Band Theory
• Beyond Dirac and Weyl fermions: Unconventional quasiparticles in conventional crystals
• Phase transition between the quantum spin Hall and insulator phases in 3D: emergence of a topological gapless phase
• Experimental observation of Weyl points
• Topological nodal line semimetals with and without spin-orbital coupling
• Symmetry-based Indicators of Band Topology in the 230 Space Groups
• Topological Semimetals
• Nodal-chain metals
• Finite-Size Scaling of the Ground State Parameters of the Two-Dimensional Heisenberg Model
• Quantum criticality and universal scaling of a quantum antiferromagnet
• Spontaneous Magnon Decays
• Structure and Topology of Band Structures in the 1651 Magnetic Space Groups
• HORACE: software for the analysis of data from single crystal spectroscopy experiments at time-of-flight neutron instruments
• Fractional excitations in the square-lattice quantum antiferromagnet
• Weyl magnons in breathing pyrochlore antiferromagnets
• Anomalous High-Energy Spin Excitations in La2CuO4
• Tunable magnon Weyl points in ferromagnetic pyrochlores
• Filling-Enforced Gaplessness in Band Structures of the 230 Space Groups
• Topological phonons and Weyl lines in 3 dimensions
• Dirac and nodal line magnons in three-dimensional antiferromagnets
• Where is the spectral weight in magnetic neutron scattering in the cuprates?
• Spin Waves and magnetic exchange interactions in insulating Rb${}_{0.89}$Fe${}_{1.58}$Se${}_2$
• Absolute cross-section normalization of magnetic neutron scattering data
• Spin-1/2 J1-J2 model on the body-centered cubic lattice
• Three Dimensional Spin Web: A New Magnetic Lattice in Cu3TeO6
• Magnetic order and transitions in the spin-web compound Cu3TeO6

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• Spin-Reorientation-Driven Linear Magnetoelectric Effect in Topological Antiferromagnet Cu${}_3$TeO${}_6$
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