Observation of a discontinuous red-shift in the emission spectrum of a two-dimensional electron gas

Photoluminescence of a high-density GaAs/AlGaAs heterostructure has been in vestigated up to 60 T using a quasi-continuous magnet. At a field of 27.5 T , corresponding to a filling factor of nu = 2 of the 2DEG, we find that the dominant Fermi-edge-enhanced emission line disappears abruptly, and an ano malous luminescence line emerges concurrently with a red-shift of about 10 meV. While there are various theoretical models addressing the issue of dis continuous red-shift in the quantum Hall regimes, we find that our observat ion, in its entirety, cannot be explained by the these models. (C) 1999 Pub lished by Elsevier Science Ltd. All rights reserved.