DISPERSIVE COLLECTIVE EXCITATION MODES IN THE QUANTUM HALL REGIME

Inelastic light scattering on a weakly density-modulated 2D electron s ystem accesses the large wavevectors needed to probe electron interact ions in quantum Hall states. For nu = 1, existence of well-defined int ersubband and inter-Landau-level dispersive collective modes is demons trated. Best agreement with theoretical predictions requires an induce d-wave-vector scheme q(m) = m(pi/d), where m = integer and d is a part ial period of the modulation. Wave vectors q(m) can be induced when al tering strips of compressible and incompressible fluids decouple and c onfine electron states to strips of width d.