Acoustic plasmons and indirect intersubband excitations in tunneling-coupled GaAs-AlxGa1ÀxAs double quantum wells

In photoluminescence spectroscopy of a low-mobility two-dimensional electron gas subjected to a quantizing magnetic field, we observe an anomaly around nu= (1/3) at a very low temperature (0.1 K) and an intermediate electron density (0.9×1011 cm–2). The anomaly is explained as due to perturbation of the incompressible liquid at the Laughlin state due to close proximity of a localized charged exciton which creates a fractionally charged quasihole in the liquid. The anomaly of ~2 meV can be destroyed by applying a small thermal energy of ~0.2 meV that is enough to close the quasihole energy gap