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Trinity College Dublin

Suppression of Short-range Scattering via Hydrophobic Surfaces and the Fractional Quantum-Hall Effec

Physica Status Solidi – Rapid Research Lett. 6, pp. 376 (2012)

Being an all-surface material, the transport properties of graphene are altered by a wide range of interactions with the environment. These interactions can originate from molecular and atomic species adsorbed from the atmosphere on the graphene or from the presence of a specific substrate surface. Such interactions can lead to an unintentional doping but more crucially introduce a variety of charge-carrier scattering centres such as charged impurities, lattice strain or resonant scatterers. Here we report on the development of the fractional quantum Hall state with the filling factor 4/3 in graphene on hydrophobically rendered SiO2 surfaces at 4.2 K. The study demonstrates that this physically fundamental manybody state can be realised by strongly suppressing short-range scattering due to the elimination of localised charged scatterers usually induced by a bare SiO2 surface in contact with graphene.

Specifically, the study reveals that upon reduction of charged scatterers the increase of the ratio of mean-free-path to charge-carrier-separation prevails over the generally believed necessity for an extraordinarily high overall mobility to enable the formation of fractional quantum Hall states in graphene and, thus, provides new insight in the development of the fractional quantum Hall state in relativistic fermion systems.