Chiral plasmons without magnetic field

Justin C. W. Song, Mark S. Rudner

Published 2015-06-15Version 1

We predict a new class of collective excitations -- chiral Berry plasmons (CBPs) -- occurring generically in interacting metallic systems with nonzero Berry flux. Such systems include e.g., anomalous Hall metals and optically-pumped valley polarized 2D Dirac materials such as transition metal dichalcogenides. In this context, a unique situation arises wherein the interplay between Bloch band Berry curvature and interactions yields chiral collective modes at zero magnetic field. 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. Directly dependent on Berry flux, plasmon wave vector, and interaction strength, the mode splitting is tunable and can be large. CBPs yield clear experimental signatures such as split optical absorption peaks in a disk geometry, as well as frequency selective uni-directional propagation along the edge. Realization of CBPs will offer a new paradigm for magnetic field-free, sub-wavelength optical non-reciprocity, as well as sensitive all-optical diagnostics of topological bands.