DOUBLET STRUCTURE OF EMISSION-SPECTRA FROM FRACTIONAL QUANTUM HALL STATES

A suppression of the exciton dispersion by an incompressible quantum liquid strongly affects the recombination emission spectrum. It comprises two parts; one of them originates from a direct recombination of kappa = 0 excitons, and the other from indirect, single magnetoroton, transitions from an extensive area in k space, kappa l approximate to 1, l is the magnetic length. Intensities of the peaks show opposite temperature dependencies. We show that the minimal frequency of magnetorotons may be found from emission spectra by a proper treatment of experimental data.