Edge magnetoplasma excitations in a two-dimensional electron system have been studied in radio-frequency experiments which exhibit a strong nonlocal behavior of the plasmon dispersion. The nonlocality is shown to be caused by the diagonal conductivity ${\mathrm{\sigma }}_{\mathit{x}\mathit{x}}$, which, via a length l∝${\mathrm{\sigma }}_{\mathit{x}\mathit{x}}$, governs the spatial distribution of the plasma charge oscillations in the direction perpendicular to the plasmon wave vector, i.e., to the edge of the two-dimensional layer.

• Received 24 May 1991

DOI:https://doi.org/10.1103/PhysRevLett.67.1019