Friday, October 10, 2003
4:00 PM
Physics Building, Room 204
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"The Quantum Hall Bilayer: A New Superfluid"

Herb Fertig , University of Kentucky
[Host: E. Kolomeisky]
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 experimental observations.

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