Edge-magnetoplasma excitations in GaAs-${\mathrm{Al}}_{\mathit{x}}$${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$As quantum wires

We report the experimental observation of strongly localized edge collective excitations propagating around each individual wire in a modulation-doped GaAs-${\mathrm{Al}}_{\mathit{x}}$${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$As quantum-wire array. The excitations have been observed in radio-frequency experiments at magnetic fields in the vicinities of the filling factors ν=2 and 4. For other magnetic-field strengths or with rising temperature the high-finesse edge wave transforms abruptly into a very different type of excitation, i.e., into a strongly damped relaxation mode distributed all over the wire.