Observation of harmonic, high-field, low-frequency edge-magnetoplasma resonances for electrons on helium

Results are reported of experiments on resonant edge-magnetoplasma modes in a two-dimensional electron fluid on liquid helium in the temperature range 0.1 K < T < 1.2 K and for magnetic fields B < 6.5 T. Up to 6 harmonic modes have been observed for the first time at frequencies ω 2π below 120 kHz, where ωτ<10-2 (τ is the zero-field scattering time). Preliminary measurements suggest a minimum in the resonant linewidth as a function of temperature.