Nontrivial low-frequency topological waves at the boundary of a magnetized plasma

TL;DR

This paper reveals a new class of low-frequency topological waves in magnetized plasmas when ion motion is considered, showing their unique properties, topological nature, and potential for experimental observation.

Contribution

It introduces ion motion into the study of topological plasma waves, discovering low-frequency unidirectional waves with unique damping and topological characteristics.

Findings

Discovery of ion-dominated topological waves above ion cyclotron frequency

Opposite group velocity direction compared to high-frequency electron waves

Potential for observing these waves in space and laboratory plasmas

Abstract

The topological properties of a magnetized cold gaseous plasma have recently been explored and the existence of topologically protected edge states has been established. These studies are limited to a magnetized plasma, where ions are infinitely massive and provide a neutralizing background. When ion motion is included, a new class of low-frequency unidirectional topological waves (TSPWs) emerges in the dispersion relation. The group velocity of these waves is in the opposite direction of high-frequency topological electron waves for a given magnetic field direction. The Berry curvature and Chern numbers are calculated to establish nontrivial topological phase. Additionally, we demonstrate a unique characteristic of ion dominated TSPW propagating above the ion cyclotron frequency: their collisionless damping via coupling to the continuum of lower-hybrid resonant modes localized inside a smooth plasma-vacuum interface. These finding broadens the possible applications and observations of these exotic excitations in space and laboratory plasmas.