MAGNETOOPTICS OF THE INCOMPRESSIBLE FERMI-LIQUID AND OF THE WIGNER SOLID

We have studied the magnetic field dependence of the spectral position of the luminescence line due to radiative recombination of two-dimensional electrons in the extreme quantum limit. We verify the recent theoretical prediction that the spectral position of the line reflects the mean energy of the electrons and find downward cusps at fractional filling factors. From the strength of these cusps we derive values for the fractional quantum Hall effect gaps and their dependence on the magnetic field. We also investigate the influence of an electric field on the properties of the additional luminescence line which appears in the Wigner solid regime. We find a threshold enhancement of the intensity of this line, which is accompanied by an appearance of additional noise, which we associate with a sliding of the pinned Wigner solid by the electric field. Our results indicate that the melting of the Wigner solid occurs in two steps and can be characterized by two critical temperatures.