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Friday, October 10, 2003
Physics Building, Room 204
Note special time.
[Host: E. Kolomeisky]
University of Kentucky
"The Quantum Hall Bilayer: A New Superfluid"
Superfluids and superconductors are known to possess a
unique stiffness related to the phase of their groundstate wavefunctions.
Under appropriate circumstances, double layer quantum Hall systems
possess an analogous stiffness that may be understood in terms
of a condensation of particle-hole pairs. The relation between these
systems has motivated both theoretical and experimental efforts
to find properties in the bilayer quantum Hall system usually associated
with superfluids. Most prominently, an effect reminiscent of
Josephson tunneling has been observed in experiments with high quality
samples, although there is considerable dissipation whose origin
is not understood. Using a renormalization group analysis and
results from Langevin dynamics simulations, we demonstrate
that the likely source of dissipation is vortices in the
phase degree of freedom. Vortex pairs are shown to have a
very unusual thermal deconfinement transition in this system, and can
also be broken apart at low temperature by disorder. In the latter
case, simulations show the system possesses properties reminiscent
of a glassy state which qualitatively account for many of the
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