Crossover from Coulomb blockade to quantum Hall effect in suspended graphene nanoribbons

TL;DR

This study investigates the transition from Coulomb blockade to quantum Hall effect in suspended graphene nanoribbons, revealing how magnetic fields influence electronic transport and correlation effects in these nanoscale systems.

Contribution

It provides experimental insights into the crossover between Coulomb blockade and quantum Hall regimes in suspended graphene nanoribbons, highlighting phenomena not observable in substrate-supported ribbons.

Findings

Transport gap due to Coulomb islands is suppressed by magnetic field.

Quantum Hall conductance plateaus appear at moderate magnetic fields.

Electronic correlations dominate at higher magnetic fields.

Abstract

Suspended graphene nano-ribbons formed during current annealing of suspended graphene flakes have been investigated experimentally. Transport measurements show the opening of a transport gap around charge neutrality due to the formation of "Coulomb islands", coexisting with quantum Hall conductance plateaus appearing at moderate values of magnetic field $B$. Upon increasing $B$, the transport gap is rapidly suppressed, and is taken over by a much larger energy gap due to electronic correlations. Our observations show that suspended nano-ribbons allow the investigation of phenomena that could not so far be accessed in ribbons on SiO$_2$ substrates.