Weak localization in graphene: theory, simulations, and experiments.

Victor Yu,Eric Whiteway,Michael Hilke,Mathieu Massicotte

doi:10.1155/2014/737296

Victor Yu, Eric Whiteway + Show 2 more

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https://doi.org/10.1155/2014/737296

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Abstract

We provide a comprehensive picture of magnetotransport in graphene monolayers in the limit of nonquantizing magnetic fields. We discuss the effects of two-carrier transport, weak localization, weak antilocalization, and strong localization for graphene devices of various mobilities, through theory, experiments, and numerical simulations. In particular, we observe a minimum in the weak localization and strong localization length reminiscent of the minimum in the conductivity, which allows us to make the connection between weak and strong localization. This provides a unified framework for both localizations, which explains the observed experimental features. We compare these results to numerical simulation and find a remarkable agreement between theory, experiment, and numerics. Various graphene devices were used in this study, including graphene on different substrates, such as glass and silicon, as well as low and high mobility devices.

Highlights

Graphene has attracted a considerable amount of attention due to the ease in isolating a single sheet of graphite via mechanical exfoliation [1, 2]
We presented a comprehensive picture of the observed magnetoresistance in graphene spanning all disorder levels
Localization becomes the dominant mechanism, where the field dependence can be understood in terms of the field dependent localization length, which interestingly follows the field dependence of the coherent return probability and the field dependence of the weak localization (WL) correction

Summary

Introduction

Graphene has attracted a considerable amount of attention due to the ease in isolating a single sheet of graphite via mechanical exfoliation [1, 2]. A striking example is the quantum Hall effect, where the Hall conductance quantization occurs in steps of 4e2/h, because of the spin and valley degeneracy, and the Landau level quantization is proportional to √B, where B is the perpendicular magnetic field component. This square root dependence leads to a very large lowest Landau level splitting, where the field quantization has been observed up to room temperature [7]. While the fourfold degeneracy can be lifted at very high fields in high mobility graphene, it is invisible at lower fields, which is the focus of this work

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