Novel relativistic plasma excitations in a gated two-dimensional electron system

A new mode is discovered in microwave response of a two-dimensional electron system (2DES) covered by a conducting top gate in the relativistic regime for which the 2D conductivity σ_2D>c/2π. This mode shows a very unusual frequency and amplitude dependence on the magnetic field, conductivity, gate geometry, and separation from the 2DES, and survives for temperatures up to 300 K, allowing for new room-temperature microwave and terahertz applications.