Optical investigations of the integer and fractional quantum Hall effects: Energy plateaus, intensity minima, and line splitting in band-gap emission

Plateaus in the electron-hole recombination energy and minima in the peak intensity at integer and fractional filling factors occur in the luminescence from ultrahigh-mobility GaAs single quantum wells. At Landau and spin gaps the regions of plateaus and intensity minima broaden as the temperature is reduced, in consort with the transport Hall resistance. A sharp intensity minimum and peak shift is seen at =2/3, while higher-field fractions are characterized by a splitting in the luminescence. The optical anomalies are directly related to the position of the Fermi energy in localized transport states.