Quantum Hall resistances of multiterminal top-gated graphene device

TL;DR

This study measures four-terminal quantum Hall resistances in a top-gated graphene device, revealing asymmetric resistances and unexpected transmission values, providing insights into edge state behavior and device characterization.

Contribution

It introduces a four-terminal measurement scheme for graphene, observing asymmetric quantum Hall resistances and unexpected edge state transmission, advancing understanding of edge state dynamics.

Findings

Asymmetric quantum Hall resistances observed

Most resistances match equal edge state population models

Unexpected 5/2 transmission suggests incomplete mode mixing or counter-propagating states

Abstract

Four-terminal resistances, both longitudinal and diagonal, of a locally gated graphene device are measured in the quantum-Hall (QH) regime. In sharp distinction from previous two-terminal studies [J. R. Williams \textit{et al.}, Science {\bf 317}, 638 (2007); B. \"{O}zyilmaz \textit{et al.}, Phys. Rev. Lett. {\bf 99}, 166804 (2007)], asymmetric QH resistances are observed, which provide information on reflection as well as transmission of the QH edge states. Most quantized values of resistances are well analyzed by the assumption that all edge states are equally populated. Contrary to the expectation, however, a 5/2 transmission of the edge states is also found, which may be caused by incomplete mode mixing and/or by the presence of counter-propagating edge states. This four-terminal scheme can be conveniently used to study the edge-state equilibration in locally gated graphene devices as well as mono- and multi-layer graphene hybrid structures.