Admittance Measurement for a Quantum Point Contact in Multiterminal Quantum Hall Device

We present admittance measurements for a quantum point contact embedded in a multiterminal quantum Hall system, using a time-resolved technique. The real part of ac admittance agrees well with conventional dc conductance, while the imaginary part shows a crossover between inductive and capacitive admittance, as theoretically predicted in the low-frequency limit. Multiterminal measurements with different chiralities of edge channels ensure that possible extrinsic coupling is negligibly small. The characteristic capacitance in our device is estimated from dependence of the imaginary part on the frequency. (C) 2011 The Japan Society of Applied Physics