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Weyl magnetoplasma waves in magnetic Weyl semimetals

Yuanzhao Wang, Oleg V. Kotov, Dmitry K. Efimkin

Abstract

Weyl degeneracies in spectra of magnetoplasma waves enable nonreciprocal energy flow and topologically protected modes, yet conventional materials require impractical magnetic fields to operate. Developing an effective Hamiltonian framework for magnetic Weyl semimetals, we show that these systems overcome the limit, hosting Weyl magnetoplasma physics at zero field due to their giant intrinsic anomalous Hall response. The resulting topology supports nonreciprocal modes localized at magnetic domain walls, including a pair of topological "Fermi-arc-like modes and additional bound states. These effects are fully developed across a broad THz window, and we propose feasible experimental routes for their detection.

Weyl magnetoplasma waves in magnetic Weyl semimetals

Abstract

Weyl degeneracies in spectra of magnetoplasma waves enable nonreciprocal energy flow and topologically protected modes, yet conventional materials require impractical magnetic fields to operate. Developing an effective Hamiltonian framework for magnetic Weyl semimetals, we show that these systems overcome the limit, hosting Weyl magnetoplasma physics at zero field due to their giant intrinsic anomalous Hall response. The resulting topology supports nonreciprocal modes localized at magnetic domain walls, including a pair of topological "Fermi-arc-like modes and additional bound states. These effects are fully developed across a broad THz window, and we propose feasible experimental routes for their detection.
Paper Structure (6 sections, 31 equations, 5 figures)

This paper contains 6 sections, 31 equations, 5 figures.

Table of Contents

  1. Axion electrodynamics perspective
  2. Chern number calculation
  3. The fate of domain-wall-trapped topological modes: a perturbative perspective
  4. The perturbation theory framework
  5. Wave functions and matrix elements
  6. The spectrum of MP waves for sharp and smooth domain wall profiles

Figures (5)

  • Figure 1: Dispersion of magnetoplasma waves in a magnetic Weyl semimetal, comprising longitudinal Langmuir (plasma) oscillations and two transverse circularly polarized modes of left- (L) and right-handed (R) helicity. These polarizations are well defined only for propagation along the gyrotropic axis ($z$), where branch decoupling occurs and a pair of Weyl nodes (blue dots) is formed.
  • Figure 2: Analytical spectrum of bulk (shaded regions) and DW-confined (lines) MP waves for the simplified profile in Eq. (\ref{['simplifiedDW']}) at $k_z = 0$, exhibiting two topological DW modes(blue and red) consistent with bulk--edge correspondence.
  • Figure 3: The spectrum of the MP waves for Bloch (top row) and Néel (bottom row) DW profiles at $\bar{c}k_z/\omega_\mathrm{p}=0$ (left column), $1$ (middle column), and $2$ (right column). While the Kelvin- and Yanai-like modes exhibit distinct behaviour at small $\bar{c}k_z/\omega_\mathrm{p}$, their dispersions become qualitatively similar at intermediate and large wave vectors.
  • Figure 4: The dispersion of magnetoplasma waves across reciprocal-space sections perpendicular to the gyrotropy axis, together with the corresponding topological Chern numbers. The exchange of Chern numbers at the crossing of two branches confirms their Weyl nature.
  • Figure 5: Spectrum of bulk (shaded regions) and DW-confined (lines) MP waves for the simplified profile in Eq. (\ref{['simplifiedDW']}) at $k_z = 0$, calculated analytically (a) and numerically (b).