Observation of axisymmetric dark plasma excitations in a two-dimensional electron system

Resonant microwave absorption of two-dimensional electron systems in AlGaAs/GaAs heterostructures with a single Corbino disk geometry has been studied. Axisymmetric dark plasmon modes have been excited using a near-field excitation technique, and their magnetodispersion have been determined in the presence of a perpendicular magnetic field. Plasma excitations observed have been compared to bright plasmon modes in a single disk of identical geometry. Dark plasmon modes have been found to have considerably longer lifetimes compared to bright plasmon modes due to the inhibition of superradiant losses.