Asymmetric Cherenkov Emission in a Topological Plasmonic Waveguide

Here, we investigate the Cherenkov emission by an array of moving electric charges in the vicinity of a topologically nontrivial gyrotropic material. It is shown that the nonreciprocal material response may result in a robustly asymmetric Cherenkov emission, such that the spectrum of the emitted radiation and the stopping power depend strongly on the sign of the particle velocity. It is demonstrated that the main emission channels are determined by the unidirectional edge states supported by the topological material. We consider as examples both magnetized plasmas and Weyl semi-metals. The latter may exhibit a spontaneous nonreciprocal response without a biasing magnetic field.