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HL: Fachverband Halbleiterphysik

HL 37: Symposium Graphene

HL 37.4: Hauptvortrag

Donnerstag, 29. März 2007, 11:30–12:00, H15

News from the quantum Hall effects in graphene — •Uli Zeitler — High Field Magnet Laboratory, Institute for Molecules and Materials, Radboud University Nijmegen, NL-6525 ED Nijmegen

Single-layer and bilayer graphene, only recently synthesized truly two-dimensional crystals [1], display two totally new classes of quantum Hall effects (QHEs). Single-layer graphene can be characterized by chiral massless charged Dirac fermions, leading to a half-integer QHE of four-fold degenerate Landau levels [2,3]. In high magnetic fields (30 T) the QHE persists up to room temperature [4] which may open up new vistas for high temperature quantum metrology. For bilayers, a new-type of integer QHE appears [5] where the N=0 quantum Hall plateau is missing. These observations can be tracked down to relativistic particles with a finite mass. They display an eight-fold degenerate Landau level at zero energy containing both electrons and holes simultaneously.

This work was done in collaboration with Kostya Novoselov, S.V. Morozov, D. Jiang, F. Schedin, and A.K. Geim (University of Manchester); E. McCann and V.I. Fal’ko (Lancaster University) and M.I. Katsnelson and J.C. Maan (Radboud University Nijmegen).

[1] K.S. Novoselov et al., Science 306, 666 (2004). [2] K. Novosolov et al., Nature 438, 197 (2005) [3] Y. Zhang et al., Nature 438, 201 (2005). [4] K. Novosolov et al., to be published. [5] K. Novosolov et al., Nature Physics 2, 177-180 (2006).