University of
California, Davis
Physics Department
Condensed Matter Seminar
**********************************
Dr. Helmut Katzgraber
Theoretische Physik, ETH Zurich
"Typical versus average superfluid density:
Understanding the vortex glass phase"
There have been conflicting claims as to whether the
superfluid density vanishes in the vortex glass phase, with Fisher,
Fisher and Huse arguing that it is finite and Korshunov predicting that
it is zero. As the vortex glass is commonly described by the gauge
glass model, we numerically compute the superfluid density of this
model by Monte Carlo simulations. Because the average free energy is
independent of a twist angle, it is expected that the average
superfluid density vanishes. This is not necessarily the case for the
typical (median) value, which is non-zero, because the distribution of
the superfluid density among different disorder realizations is very
asymmetric. Finally, we show that the data for the superfluid density
is well described by a generalized extreme value distribution with a
nonzero "location parameter".
Thursday, May
13, 2004
4:10 p.m., 416 Phy/Geo