Observation of Topologically-Protected Electromagnetic Edge Modes on Gaseous Plasma Surface at Angle to Applied Magnetic Field

At the surface of magnetized gaseous plasma, it has been predicted that, in the band gap between the first and second bulk modes, unidirectional topologically-protected electromagnetic edge modes can exist which propagate at an angle to the applied magnetic field. This presentation will present the first experimental detection of these edge modes by observing non-reciprocal power attenuation across a metasurface waveguide interfacing with plasma inside a gas discharge tube. With an applied field of 87mT and a plasma frequency of 10 GHz, we map the frequency of the detected edge modes as propagation angle is varied from 0° to 38°, which matches well with computational results.