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Electronic states on the surface of graphite Guohong Li, Adina Luican, Eva Y. Andrei*

Summary: Electronic states on the surface of graphite
Guohong Li, Adina Luican, Eva Y. Andrei*
Department of Physics and Astronomy, Rutgers Univsersity, Piscataway, NJ 08854, USA
Elsevier use only: Received date here; revised date here; accepted date here
Graphite consists of graphene layers in an AB (Bernal) stacking arrangement. The introduction of defects can reduce the
coupling between the top graphene layers and the bulk crystal producing new electronic states that reflect the degree of
coupling. We employ low temperature high magnetic field scanning tunneling microscopy (STM) and spectroscopy (STS) to
access these states and study their evolution with the degree of coupling. STS in magnetic field directly probes the
dimensionality of electronic states. Thus two dimensional states produce a discrete series of Landau levels while three
dimensional states form Landau bands providing a clear distinction between completely decoupled top layers and ones that
are coupled to the substrate. We show that the completely decoupled layers are characterized by a single sequence of Landau
levels with square root dependence on field and level index indicative of massless Dirac fermions. In contrast weakly coupled
bilayers produce special sequences reflecting the degree of coupling, and multilayers produce sequences reflecting the
coexistence of massless and massive Dirac fermions. In addition we show that the graphite surface is soft and that an STM tip
can be quite invasive when brought too close to the surface and that there is a characteristic tip-sample distance beyond which
the effect of sample tip interaction is negligible.
2009 Elsevier Science. All rights reserved
Keywords: A) surfaces and interfaces;(C) scanning tunneling microscopy; (D) quantum Hall effect;


Source: Andrei, Eva Y. - Department of Physics and Astronomy, Rutgers University


Collections: Materials Science; Physics