Experimental search for a topological gaseous plasmon polariton at the Large Plasma Device

A change in the topology of waves on separate sides of an interface guarantees the existence of topologically protected waves that are localized to the interface. Here we investigate a gaseous plasmon polariton (GPP), an electromagnetic wave that owes its existence to topology. It exhibits helical motion and is localized along the boundary between a magnetized plasma and a vacuum. Using parameters appropriate for the Large Plasma Device (LAPD), we conduct numerical simulations to check the ability of the LAPD to sustain the GPP. We then perform an experiment at LAPD to look for the GPP. By observing the propagation of GHz microwaves along the sharp density gradient near the plasma edge, we find preliminary evidence for the localization of the wave that is consistent with theoretical and computational predictions for the GPP.