Proximity Plasma Excitations In Disk And Ring Geometries

We have investigated plasma excitations in the hybrid system with a disk-shaped metallic gate introduced on top of an infinite two-dimensional electron system. The proximity plasma excitations have been identified and explored in this partially-gated system, and the results are compared with the behavior of ordinary gated plasmons excited in a system with the disk geometry. Significantly, with the change of the gate geometry from a disk to a narrow ring, we observed the transformation of proximity plasmons with linear dispersion into those having square-root dependence on the wave vector. Our experimental findings show good agreement with the theory.