Observation of excess conductance of a constricted electron gas in the fractional quantum Hall regime

We present experimental results on the conductance of a two-dimensional electron system of filling factor ν_2D in the fractional quantum Hall regime, containing a constricted region of lower filling factor ν_c. Conductance fluctuations are observed as a function of the voltage on the gate defining the constriction. The temperature dependence of the fluctuations exhibits three distinct regimes, governed by ν_c. For temperatures below 100 mK, and for ν_2D=1/3, one anomalous peak increases to a value above the quantized conductance ν_2D(e²/h) of the bulk.