Relativistic plasma excitations in two-dimensional electron systems

Microwave absorption of a two-dimensional electron system (2DES) with a disk-shaped metallic gate, electrically connected to the 2DES perimeter, has been investigated. In addition to the dipole proximity plasma excitation, special "charged" relativistic plasmon has been observed. It has demonstrated very unusual behaviour, including dependency of its properties on the external connecting wire parameters. The observed properties are supposed to be connected with the hybridization of this plasmon and the photon mode in the external connection wire.