Inter-edge magnetoplasmons in inhomogeneous two-dimensional electron systems

New collective excitations of the inhomogeneous two-dimensional (2D) electron system-inter-edge magnetoplasmons (IEMP)-are predicted. IEMP propagate along the boundary of two contacting 2D regions with different conductivities. The edge magnetoplasmon propagating along the outer edge of a 2D layer is a special case of IEMP. Both the two half-planes and the disc geometry are considered. Two branches of the IEMP spectrum are found. The upper branch with frequency larger than the cyclotron frequency omega _c decays even in the collisionless limit on account of the emission of the 'bulk' 2D magnetoplasmons into the region of the 2D layer with the smaller electron density. The frequency of the lower IEMP branch is smaller than omega _c; its damping is very small in strong magnetic fields. In quantizing magnetic fields B the frequency and damping of the low-frequency IEMP mode oscillate with B. It is shown that the cyclotron resonance splitting in inhomogeneous 2D electron systems can result from the strong coupling between the IEMP and the cyclotron resonance branches. Recent experimental data are discussed.