Experimental detection of topological surface waves at a magnetized plasma interface in the Voigt configuration

This Letter reports on the experimental observation of a topologically non-trivial electromagnetic wave propagating perpendicular to an applied magnetic field at the interface between a gaseous plasma and metal. The resulting one-way wave-guiding is a demonstration of topological non-reciprocity associated with the edge state within the gap between the lower and upper X-modes of the bulk plasma. Electromagnetic wave excitation using simple dipole antennas results in a 20 dB isolation at 10.8 GHz with the plasma biased with a magnetic field of 87 mT. We show that reducing the magnetic field gradually diminishes the strength of the transmitted wave due to the closing of the X-mode gap.