Chiral plasmons without magnetic field

TL;DR

This paper predicts a new class of chiral Berry plasmons in 2D materials, which exhibit magnetic-field-free, non-reciprocal optical responses due to Berry curvature effects, with potential applications in mid-IR to THz technologies.

Contribution

It introduces chiral Berry plasmons in 2D systems, demonstrating their existence and properties without magnetic fields, and proposes experimental setups for their realization.

Findings

Chiral plasmonic modes exist at zero magnetic field due to Berry curvature.

CBPs are confined to system boundaries without topological edge states.

Tunable splittings of CBPs can reach tens of THz.

Abstract

Plasmons, the collective oscillations of interacting electrons, possess emergent properties that dramatically alter the optical response of metals. We predict the existence of a new class of plasmons -- chiral Berry plasmons (CBPs) -- for a wide range of two-dimensional metallic systems including gapped Dirac materials. As we show, in these materials the interplay between Berry curvature and electron-electron interactions yields chiral plasmonic modes at zero magnetic field. The CBP modes are confined to system boundaries, even in the absence of topological edge states, with chirality manifested in split energy dispersions for oppositely directed plasmon waves. We unveil a rich CBP phenomenology and propose setups for realizing them, including in anomalous Hall metals and optically-pumped 2D Dirac materials. Realization of CBPs will offer a new paradigm for magnetic field-free, sub-wavelength optical non-reciprocity, in the mid IR-THz range, with tunable splittings as large as tens of THz, as well as sensitive all-optical diagnostics of topological bands.