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arXiv · 1703.08545

Dirac and nodal line magnons in three-dimensional antiferromagnets

Kangkang Li·Chenyuan Li·Jiangping Hu·Yuan Li·Chen Fang
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Abstract

We study the topological properties of magnon excitations in three-dimensional antiferromagnets, where the ground state configuration is invariant under time-reversal followed by space-inversion ($PT$-symmetry). We prove that Dirac points and nodal lines, the former being the limiting case of the latter, are the generic forms of symmetry-protected band crossings between magnon branches. As a concrete example, we study a Heisenberg spin model for a "spin-web" compound, Cu$_3$TeO$_6$, and show the presence of the magnon Dirac points assuming a collinear magnetic structure. Upon turning on symmetry-allowed Dzyaloshinsky-Moriya interactions, which introduce a small non-collinearity in the ground state configuration, we find that the Dirac points expand into nodal lines with nontrivial $Z_2$-topological charge, a new type of nodal lines unpredicted in any materials so far.

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Kangkang Li, Chenyuan Li, Jiangping Hu, Yuan Li, Chen Fang. 2017-11-05. Dirac and nodal line magnons in three-dimensional antiferromagnets. https://doi.org/10.1103/physrevlett.119.247202

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