Abstract
Quantum transport measurements on etched graphene nanoribbons encapsulated in hexagonal boron nitride (hBN) are reported. At zero magnetic field, the devices behave qualitatively very similar to those reported for graphene nanoribbons on SiO2 or hBN, but exhibit a considerably smaller transport gap. At magnetic fields of around 3 T, the transport behavior changes significantly and is dominated by a much larger energy gap induced by electron–electron interactions which completely suppress the transport. This energy gap increases with a slope in the order of 3–4 meV T−1, reaching values of up to 30 meV at 9 T.
Highlights
Graphene nanoribbons offer an interesting playground to study mesoscopic physics at the nanoscale combining size confinement effects and the Dirac fermion nature of electrons in graphene [1,2,3]
High quality graphene has already revealed anomalous patterns in the magnetoconductance called Hofstadter’s butterfly due to the moire superlattice of graphene/hexagonal boron nitride (hBN) heterostructures [11, 12] or quantum Hall ferromagnetism at the Dirac point [13,14,15,16]. The latter has been realized in high mobility suspended graphene nanoribbons [17] but these suffer from the limited control in the fabrication process and gate tunability [18]
An alternative way to achieve very high electronic quality is placing graphene on hexagonal boron nitride which can significantly reduce the disorder potential [26,27,28,29,30]
Summary
Graphene nanoribbons offer an interesting playground to study mesoscopic physics at the nanoscale combining size confinement effects and the Dirac fermion nature of electrons in graphene [1,2,3]. High quality graphene has already revealed anomalous patterns in the magnetoconductance called Hofstadter’s butterfly due to the moire superlattice of graphene/hBN heterostructures [11, 12] or quantum Hall ferromagnetism at the Dirac point [13,14,15,16] The latter has been realized in high mobility suspended graphene nanoribbons [17] but these suffer from the limited control in the fabrication process and gate tunability [18]. A step towards further reducing this type of disorder is to encapsulate graphene in hBN [28], which prevents process-induced contaminations on the graphene flake, the edges are still exposed This results in substrate-supported devices with reproducibly high electronic quality and enables the observation of quantum phenomena like quantized conductance in sub-micron structured graphene constrictions [34, 35]. The resulting nanoribbons are contacted in a second EBL step and a subsequent metal evaporation (a)
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