Article abstract
Nature Physics 4, 144 - 148 (2008)
Published online: 25 November 2007 | doi:10.1038/nphys781
Subject Category: Condensed-matter physics
Observation of electron–hole puddles in graphene using a scanning single-electron transistor
J. Martin1, N. Akerman1, G. Ulbricht2, T. Lohmann2, J. H. Smet2, K. von Klitzing2 & A. Yacoby1,3
Abstract
The electronic structure of graphene causes its charge carriers to behave like relativistic particles. For a perfect graphene sheet free from impurities and disorder, the Fermi energy lies at the so-called 'Dirac point', where the density of electronic states vanishes. But in the inevitable presence of disorder, theory predicts that equally probable regions of electron-rich and hole-rich puddles will arise. These puddles could explain graphene's anomalous non-zero minimal conductivity at zero average carrier density. Here, we use a scanning single-electron transistor to map the local density of states and the carrier density landscape in the vicinity of the neutrality point. Our results confirm the existence of electron–hole puddles, and rule out extrinsic substrate effects as explanations for their emergence and topology. Moreover, we find that, unlike non-relativistic particles the density of states can be quantitatively accounted for by considering non-interacting electrons and holes.
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot 76100, Israel
- Max-Planck-Institut für Festkörperforschung, Heisenbergstrasse 1, D-70569 Stuttgart, Germany
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
Correspondence to: A. Yacoby1,3 e-mail: yacoby@physics.harvard.edu
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