Light Scattering by Magnetorotons of Collective Excitations in the Fractional Quantum Hall Regime
01 January 2002
Magnetorotons in the dispersions of collective gap excitation modes of fractional quantum Hall liquids are measured by resonant inelastic light scattering. Two deep magnetoroton minima are observed at nu = 2/5, while a single deep minimum is resolved at nu = 1/3. The results support Chern-Simons and composite fermion calculations that predict multiple roton minima for states with nu > 1/3.