Edge-Plasmon-Induced Magnetization in Higher Chern Insulators

Abstract

Higher Chern insulators host multiple dissipationless chiral edge states, one per unit of Chern number. We study the collective plasmon modes of these edge states at a domain wall between Chern numbers $\mathcal{C}$ and $-\mathcal{C}$, using a semiclassical model with Coulomb interactions. The plasmon dispersion is linear at long wavelengths, with a velocity that increases linearly with $\mathcal{C}$. As in conventional two-dimensional metals, the edge plasmon generates an elliptically polarized electric field that decays into the bulk and drives electrons in circular orbits, producing a static orbital magnetization (inverse Faraday effect). For topological edge plasmons, the magnetization has a nontrivial spatial profile set by two competing length scales: the finite extent of the edge states and the plasmon wavelength. At fixed edge-charge amplitude, it grows strongly with $\mathcal{C}$. At the domain wall, it approaches a finite plateau at low frequency and decays as $1/ω^2$ at high frequency. Its temperature dependence is nonmonotonic, with a maximum at an intermediate temperature. These results show how the Chern number controls plasmon-induced magnetization, in contrast to conventional edge plasmons.