Magnetoplasmon molecule

We investigate a two-dimensional electron system in an external magnetic field. An intrinsic four-particle excitation of the electron system, which we term a magnetoplasmon molecule, is observed. The molecule comprises two identical electrons and two Fermi holes with opposite spins. Both electrons and one Fermi hole participate in the collective plasma oscillations of the electron system, whereas the second Fermi hole neutralizes the excess electronic charge. We examine the interaction between the magnetoplasmon molecule and a magnetoexciton condensate.