Magnon-induced phononic Chern insulator

Rui-Chang Shen; Yihao Yang; Haoran Xue

cond-mat.mes-hallAug 27, 2026

Magnon-induced phononic Chern insulator

Authors: Rui-Chang Shen, Yihao Yang, Haoran Xue

Organizations: Department of Physics, The Chinese University of Hong Kong, Shatin, Hong Kong SAR, China · State Key Laboratory of Extreme Photonics and Instrumentation, ZJU-Hangzhou Global Scientific and Technological Innovation Center, Zhejiang University, Hangzhou 310027, China. · The Electromagnetics Academy at Zhejiang University, College of Information Science and Electronic Engineering, Zhejiang University, Hangzhou 310027, China. · Zhejiang Key Lab. of Intelligent Electromagnetic Control and Advanced Electronic Integration, Jinhua Institute of Zhejiang University, Zhejiang University, Jinhua 321099, China. ·

Abstract

High-frequency artificial phononic crystals offer a low-loss platform compatible with on-chip integration, yet realizing Chern phononic phases at GHz frequencies remains challenging. Here, we propose a magnon-induced phononic Chern insulator in a honeycomb phononic crystal hybridized with ferromagnetic islands at the hexagon centers. A circularly polarized Kittel mode couples to the surrounding phonons with a phase winding, which breaks time-reversal symmetry and opens a full Chern gap. In the large-detuning regime, this mechanism leads to an effective Haldane-type phononic model with magnon-induced complex hopping. By tuning the magnon-phonon interaction, the full hybrid system accesses Chern phases with tunable Chern numbers |C|=1 and |C|=2. The predicted gaps can exceed realistic phonon and magnon linewidths, enabling their observation in GHz acoustic devices. Our work establishes chiral magnon--phonon hybridization as a route to magnetically reconfigurable topological phononics.

Figures & tables

Figure 1: (a) Schematic of Human-Agentic hybrid workflow. (b) A honeycomb phononic crystal with one phonon mode on each A and B sublattice site. A magnetic island at the plaquette center supports a right-handed circular Kittel mode. The six surrounding phononic sites are labeled in their physical counterclockwise order as $\mathrm{A}_{1},\mathrm{B}_{1},\mathrm{A}_{2},\mathrm{B}_{2},\mathrm{A}_{3},\mathrm{B}_{3}$ . Their radial vectors are $\bm{d}_{\alpha,i}=a_{0}(\cos\theta_{\alpha,i},\sin\theta_{\alpha,i})$ , with $\theta_{\mathrm{A},i}=2\pi(i-1)/3$ , $\theta_{\mathrm{B},i}=(2i-1)\pi/3$ , and $a_{0}$ is the distance from the plaquette center to each surrounding phononic site. (c) Momentum-space intensity of the magnon–phonon terms $|G_{\rm A}(\bm{k})|^{2}$ and $|G_{\rm B}(\bm{k})|^{2}$ , showing that the magnon couples selectively to sublattice A at $\rm K$ and to sublattice B at $\rm K^{\prime}$ . (d) Schematic of the magnon-induced effective phonon hopping, showing $H_{\rm eff}-H_{\rm ph}$ , where only the magnon-induced coupling between phonons is depicted. The coupling phase is illustrated in the right panel. Each NN bond receives virtual-magnon contributions from the center magnons of its two adjacent plaquettes.

Figure 2: (a) Bulk band structures in the absence (gray dashed curves) and presence (colored solid curves) of the magnon-phonon coupling, which explicitly opens a gap at the Dirac points. The lower, middle and upper bands have the Chern numbers $C=(-1,~+1,~0)$ , respectively. (b) The corresponding strip spectrum for $g=0.4$ , with periodic boundary conditions applied along $\bm{a}_{1}=a_{0}(3,\sqrt{3})/2$ . (c) Spatial distribution of the edge states, calculated as the sum of the probability of all localized modes within the bandgap. Parameters are set as $t=1$ and $\delta_{\omega}=3.2$ .

Figure 3: (a) and (b) Chern-number phase diagrams of the lowest band and the middle band, respectively, as functions of the magnon detuning $\delta_{\omega}$ and the magnon–phonon coupling strength $g$ , with $t=1$ . The dashed curve $4g^{2}=t^{2}+t\delta_{\omega}$ , marks the gap-closing condition at the $\rm M$ point, while the vertical dashed line in (b) indicates the $\Gamma$ -point transition at $\delta_{\omega}=3t$ . (c) and (d) Plots of bulk bandgaps $\Delta_{1}$ (gap between the lower and middle bands) and $\Delta_{2}$ (gap between the middle and upper bands), respectively, as functions of $\delta_{\omega}$ and $g$ .

Materials Science

Materials science studies how composition, structure, processing, and defects determine material properties and how to design useful materials.

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From butterfly wings to remnants of nuclear detonation, aperiodic order repeatedly emerges in nature, often exhibiting reduced sensitivity to boundaries and symmetry constraints. Inspired by this principle, a paradigm shift is introduced in nanomechanical resonator design from periodic to aperiodic structures, focusing on a special class: quasicrystals (QCs). Although soft clamping enabled by phononic stopbands has become a central strategy for achieving high-

Q_m

nanomechanical resonators, its practical realization has been largely confined to periodic phononic crystals, where band structure engineering is well established. The potential of aperiodic architectures, however, has remained largely unexplored, owing to their intrinsic complexity and the lack of systematic approaches to identifying and exploiting stopband behavior. Here we demonstrate that soft clamping can be realized in quasicrystal architectures and that high-

Q_m

nanomechanical resonators can be systematically predicted through a data-driven design framework. As a representative demonstration, the 12-fold QC-based resonator obtained numerically a quality factor

Q_m \sim 10^7

and an effective mass of sub-nanograms at MHz frequencies, corresponding to an exceptional force sensitivity of

26.4

~aN/

\sqrt{\text{Hz}}

compared to previous 2D phononic crystals. These results establish QCs as a robust platform for next-generation nanomechanical resonators and open a new design regime beyond periodic order.

Abstract

Materials Science

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