Dresden 2011 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 81: Graphene: Transport

HL 81.7: Talk

Thursday, March 17, 2011, 16:15–16:30, POT 151

Transport measurements on twisted graphene monolayer systems — •Hennrik Schmidt, Thomas Lüdtke, Patrick Barthold, and Rolf J. Haug — Institut für Festkörperphysik, Leibniz Universität Hannover, D-30167 Hannover, Germany

A system of two stacked graphene monolayers which are rotated with respect to Bernal stacking exhibits electrical properties quite different to samples of single monolayers or single crystal bilayer systems(1)(2). Magnetotransport measurements at different carrier concentrations are performed on decoupled monolayers being jointly contacted. Two superimposed Shubnikov-de Haas oscillations are observed with a Berrys phase of π each, indicating parallel transport through two graphene monolayers. In the Hall resistance plateaus are observed according to the minima of these oscillations. The bottom layer screens the other one both from backgate voltage and substrate influence leading to a lower carrier concentration but also significantly increased mobilities and scattering times in the upper layer. From temperature dependent measurements the cyclotron masses are obtained showing higher values than expected for a single monolayer. This indicates a reduced Fermi velocity and therefore an interaction of the two layers. In the vicinity of the charge neutrality point an asymetric temperature damping is observed.
(1)H. Schmidt, T. Lüdtke, P. Barthold, E. McCann, V. I. Fal’ko, and R. J. Haug, Appl. Phys. Lett. 93, 172108 (2008)
(2)H. Schmidt, T. Lüdtke, P. Barthold, and R. J. Haug, Phys. Rev. B, 81, 121403(R) (2010)