Transition between electron localisation and antilocalisation in graphene

TL;DR

This paper demonstrates that graphene exhibits both electron localisation and anti-localisation effects due to quantum interference, with these effects persisting up to high temperatures around 200 K, highlighting its unique quantum transport properties.

Contribution

It provides experimental evidence of both localisation and anti-localisation in graphene, showing the influence of chirality and Berry phase on quantum interference effects.

Findings

Graphene shows negative magnetoconductance due to anti-localisation.

Quantum interference effects in graphene survive up to 200 K.

Graphene can demonstrate both localisation and anti-localisation depending on conditions.

Abstract

The wave nature of electrons in low-dimensional structures manifests itself in conventional electrical measurements as a quantum correction to the classical conductance. This correction comes from the interference of scattered electrons which results in electron localisation and therefore a decrease of the conductance. In graphene, where the charge carriers are chiral and have an additional (Berry) phase of \pi, the quantum interference is expected to lead to anti-localisation: an increase of the conductance accompanied by negative magnetoconductance (a decrease of conductance in magnetic field). Here we observe such negative magnetoconductance which is a direct consequence of the chirality of electrons in graphene. We show that graphene is a unique two-dimensional material in that, depending on experimental conditions, it can demonstrate both localisation and anti-localisation effects. We also show that quantum interference in graphene can survive at unusually high temperatures, up to T~200 K.