Admittance measurements in the quantum Hall effect regime

In this work we present an admittance study of a two-dimensional electron gas(2DEG) in thequantum Hall effect (QHE) regime. We have studied several Hall bars in different contacts configurations in the frequency range100Hz-1 MHz. Our interpretation is based on the Landauer-Buttiker theory and takes into account both the capacitance and the topology of the coaxial cables which are connected to the sample holder. We show that we always observe losses through the capacitive impedance of the coaxial cables, except in the two contacts configuration in which the cable capacitance does not influence the admittance measurement of the sample. In this case, we measure the electrochemical capacitance of the 2DEG and show its dependence with the filling factor ν.