How to probe a fractionally charged quasihole?

We report an anomalous dispersion of charged excitons in photoluminescence experiments on a two-dimensional electron gas subjected to a quantizing magnetic field around View the MathML source. We have found that the anomaly exists only at a very low temperature View the MathML source and an intermediate electron density View the MathML source. It is explained to occur due to the perturbation of the incompressible liquid at View the MathML source. The perturbation is induced by the close proximity of a localized charged exciton which creates a fractionally charged quasihole in the liquid. The intriguing experimentally observed puzzle that the anomaly can be destroyed by applying a small thermal energy of View the MathML source is thereby resolved, as this energy is enough to close the quasihole energy gap. This work presents a probe of the quasihole gap in a quantum Hall system.