Towards a Graphene-Based Quantum Impedance Standard

TL;DR

This paper demonstrates that epitaxial graphene exhibits highly accurate quantum Hall resistance under ac conditions, showing promise as a practical quantum impedance standard with potential for further improvements.

Contribution

It provides the first detailed assessment of ac quantum Hall resistance in epitaxial graphene, highlighting its superior flatness and lower capacitive losses compared to GaAs devices.

Findings

Quantum Hall plateaus in graphene are flat within 1 part in 10^7.

Graphene devices show less critical capacitive ac losses than GaAs devices.

Frequency dependence suggests stray capacitances can be minimized for better performance.

Abstract

Precision measurements of the quantum Hall resistance with alternating current (ac) in the kHz range were performed on epitaxial graphene in order to assess its suitability as a quantum standard of impedance. The quantum Hall plateaus measured with alternating current were found to be flat within one part in 10^7. This is much better than for plain GaAs quantum Hall devices and shows that the magnetic-flux-dependent capacitive ac losses of the graphene device are less critical. The observed frequency dependence of about -8x10^-8/kHz is comparable in absolute value to the positive frequency dependence of plain GaAs devices, but the negative sign is attributed to stray capacitances which we believe can be minimized by a careful design of the graphene device. Further improvements thus may lead to a simpler and more user-friendly quantum standard for both resistance and impedance.