[institut] Seminar Fizickog fakulteta

[Mirzeta Savic]

Sreda, 21. novembar 2012. godine u 11 casova u sali 661 na Fizickom
fakultetu, Studentski trg 12, III sprat

"Edge magneto-plasmons in graphene"
Dr Ivana Petković
Nanoelectronics Group, Service de Physique de l'Etat Condensé, CEA Saclay,
F-91191, Gif-sur-Yvette, France;
Department of Physics, Yale University, New Haven, Connecticut 06520, USA

Abstract: The important physics for the quantum Hall effect (QHE) takes
place on the edge of a 2-dimensional electron system (2DES), where
dissipationless chiral transport current flows, Hall charge accumulates and
the associated collective modes concentrate. The latter - Edge
Magneto-Plasmons (EMP) - are quasi one dimensional elementary excitations
which are split off from the bulk magneto-plasmon modes by the sample
boundary. Closely confined to the edge as frequency is increased, they have
been a tool of choice to investigate edge structure and dynamics of
conventional 2-dimensional electron systems. The group velocity of these
modes has two contributions, arising from the Hall conductivity and the
carrier drift at the edge.  In graphene, due to its particular dynamics and
an abrupt edge, the drift velocity is expected to be of the order of the
Fermi velocity, thus becoming experimentally accessible. We show EMP to
exist by timing the travel of narrow wave-packets on picosecond time scales
around exfoliated samples. We find chiral propagation with low attenuation
at a velocity which is quantized on Hall plateaus. We extract the carrier
drift contribution from the EMP propagation and find it to be slightly less
than the Fermi velocity, as expected for an abrupt edge. We also extract the
spatial spread of edge accumulated charge and find it to be narrower than
for soft edge systems.

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