APS March Meeting 2011
Volume 56, Number 1
Monday–Friday, March 21–25, 2011;
Dallas, Texas
Abstract: P2.00003 : Kondo effect and STM spectroscopy of Dirac electrons in graphene
9:12 AM–9:48 AM
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Author:
We show that graphene, whose low-energy quasiparticles display
Dirac like
behavior, may exhibit a
two-channel Kondo effect in the presence of magnetic impurities.
We present
a large $N $analysis for a generic spin $S $local moment coupled
to Dirac electrons
in graphene and demonstrate that the corresponding Kondo
temperature can be
tuned by an experimentally controllable applied gate voltage. We
also study
the STM spectra of these Dirac electrons in the presence of such
impurities
and demonstrate that such spectra depend qualitatively on the
position of
the impurity atom in the graphene matrix. More specifically, for
impurity
atoms atop the hexagon center, the zero-bias tunneling
conductance, as
measured by a STM, shows a peak; for those atop a graphene site,
it shows a
dip. We provide a qualitative theoretical explanation of this
phenomenon and
show that this unconventional behavior is a consequence of
conservation/breaking of pseudospin symmetry of the Dirac
quasiparticles by
the impurity. We also predict that tuning the Fermi energy to
zero by a gate
voltage would not lead to qualitative change in the shape of the
conductance
spectra when the impurity is atop the hexagon center. A similar
tuning of
the Fermi energy for the impurity atop a site, however, would
lead to a
change in the tunneling conductance from a dip to a peak via an
antiresonance. We discuss some recent experiments on a doped
graphene sample
that seem to have qualitative agreement with our theory and
suggest further
experiments to test our predictions.
To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2011.MAR.P2.3