Chiral Dirac-like fermion in spin-orbit-free antiferromagnetic semimetals

Abstract

Dirac semimetal is a phase of matter, whose elementary excitation is described by the relativistic Dirac equation. In the limit of zero mass, its parity-time symmetry enforces the Dirac fermion in the momentum space, which is composed of two Weyl fermions with opposite chirality, to be non-chiral. Inspired by the flavor symmetry in particle physics, we theoretically propose a massless Dirac-like equation yet linking two Weyl fields with the identical chirality by assuming SU(2) isospin symmetry, independent of the space-time rotation exchanging the two fields. Dramatically, such symmetry is hidden in certain solid-state spin-1/2 systems with negligible spin-orbit coupling, where the spin degree of freedom is decoupled with the lattice. Therefore, the existence of the corresponding quasiparticle, dubbed as flavor Weyl fermion, cannot be explained by the conventional (magnetic) space group framework. The four-fold degenerate flavor Weyl fermion manifests linear dispersion and a Chern number of 2, leading to a robust network of topologically protected Fermi arcs throughout the Brillouin zone. For material realization, we show that the transition-metal chalcogenide CoNb3S6 with experimentally confirmed collinear antiferromagnetic order is ideal for flavor Weyl semimetal under the approximation of vanishing spin-orbit coupling. Our work reveals a counterpart of the flavor symmetry in magnetic electronic systems, leading to further possibilities of emergent phenomena in quantum materials.

27 pages and 5 figures

References in corpus (8)

• Classification of stable three-dimensional Dirac semimetals with nontrivial topology
• Multiple types of topological fermions in transition metal silicides
• Large Fermi Arcs in Unconventional Weyl Semimetal RhSi
• Double-Weyl phonons in transition-metal monosilicides
• Type-II Weyl Points in Three-Dimensional Cold Atom Optical Lattices
• Antiferromagnetic Dirac Semimetals in Two Dimensions
• Fragility of Fermi arcs in Dirac semimetals
• Identifying, and constructing, complex magnon band topology

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• Catalog of Unconventional Magnons in Collinear Magnets
• Symmetry invariants and classes of quasiparticles in magnetically ordered systems having weak spin-orbit coupling
• The Crystallographic Spin Point Groups and their Representations
• Chiral Dirac fermion in a collinear antiferromagnet
• Group Theory on Quasisymmetry and Protected Near Degeneracy
• Structure, physical properties, and magnetically tunable topological phases in topological semimetal EuCuBi
• Constructions and Applications of Irreducible Representations of Spin-Space Groups
• Superconducting Order Parameters in Spin Space Groups: Methodology and Application
• Altermagnetic Weyl node-network semimetals protected by spin symmetry
• The emergence of net chirality in two-dimensional Dirac fermions system with altermagnetic mass
• Topological Charge Quadrupole Protected by Spin-Orbit U(1) Quasi-Symmetry in Antiferromagnet NdBiPt
• Crystalline electric field excitations in Weyl semimetal \textit{R}AlSi (\textit{R} = Ce, Pr and Nd)