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  • Open Access

Point-gap topology of damped magnon excitations in skyrmion strings

Yusuke Koyama1 and Yuki Kawaguchi1,2

  • 1Department of Applied Physics, Nagoya University, Nagoya 464-8603, Japan
  • 2Research Center for Crystalline Materials Engineering, Nagoya University, Nagoya 464-8603, Japan

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Phys. Rev. B 114, 194426 – Published 26 October, 2026

DOI: https://doi.org/10.1103/gxr7-xtsr

Abstract

We theoretically study the non-Hermitian topology of magnons with finite lifetimes due to Gilbert damping. By incorporating the spin-wave theory and perturbation theory for the Landau-Lifshitz-Gilbert equation including nonlocal damping terms, we analytically evaluate the spectral winding number for point gaps, which indicates the existence of the non-Hermitian skin effect (NHSE). We find that, in noncollinear magnetic textures, the NHSE can occur even in the absence of nonlocal damping, due to the momentum-dependent mixing of the particle and hole components of magnon eigenmodes, which is absent in collinear magnets with a single magnon band. In the presence of nonlocal damping along one direction, we show that the winding number for an energy band with a unique minimum is determined from the sign of the wave number at the band minimum. We demonstrate these results using a model that hosts a skyrmion-string lattice as a steady state. We further investigate spin-wave propagation dynamics excited by a magnetic-field pulse and show that the propagation direction changes drastically from band to band depending on the presence of local and nonlocal damping, consistent with the nontrivial winding numbers.

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Outline

Information

Phys. Rev. B 114, 194426– Published 26 October, 2026
  • Received 8 May 2026
  • Revised 21 August 2026
  • Accepted 9 October 2026
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

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