Distributed electrochemical capacitance evidenced in high-frequency admittance measurements on a quantum Hall device

Abstract

We describe high-frequency admittance measurements up to 3 GHz on a quantum point contact in a quantum Hall regime. When the excitation frequency is so high that the wavelength of the edge magnetoplasmons is comparable to the size of the system, the phase developing along the edge channels must be considered when analyzing electrochemical capacitance in admittance. The result cannot be accounted for by the local electrochemical capacitance near the quantum point contact but instead needs to be understood by considering the distributed capacitance within the sample as a whole. This implies that all electrons within the device are interacting because the screening in one-dimensional channels is extremely weak. A distributed-element model is essential for understanding the ac response in low-dimensional structures, which is analogous to that in high-frequency electrical circuits.