3 research outputs found
Topological Defects from First Order Gauge Theory Phase Transitions
We investigate the mechanism by which topological defects form in first order
phase transitions with a charged order parameter. We show how thick
superconductor vortices and heavy cosmic strings form by trapping of magnetic
flux. In an external magnetic field, intermediate objects such as strips and
membranes of magnetic flux and chains of single winding defects are produced.
At non-zero temperature, a variety of spontaneous defects of different winding
numbers arise. In cosmology, our results mean that the magnetic flux thermal
fluctuations get trapped in a primordial multi-tension string network. The
mechanism may also apply to the production of cosmic-like strings in brane
collisions. In a thin type-I superconductor film, flux strips are found to be
meta-stable while thick vortices are stable up to some critical value of the
winding number which increases with the thickness of the film. In addition, a
non-dissipative Josephson-like current is obtained across the strips of
quantized magnetic flux.Comment: Corrections made on sections 4,5. Higher quality figures in published
versio
Fluxoid formation: size effects and non-equilibrium universality
Simple causal arguments put forward by Kibble and Zurek suggest that the
scaling behaviour of condensed matter at continuous transitions is related to
the familiar universality classes of the systems at quasi-equilibrium. Although
proposed 25 years ago or more, it is only in the last few years that it has
been possible to devise experiments from which scaling exponents can be
determined and in which this scenario can be tested. In previous work, an
unusually high Kibble-Zurek scaling exponent was reported for spontaneous
fluxoid production in a single isolated superconducting Nb loop, albeit with
low density. Using analytic approximations backed up by Langevin simulations,
we argue that densities as small as these are too low to be attributable to
scaling, and are conditioned by the small size of the loop. We also reflect on
the physical differences between slow quenches and small rings, and derive some
criteria for these differences, noting that recent work on slow quenches does
not adequately explain the anomalous behaviour seen here.Comment: 7 pages, 4 figures, presentation given at CMMP 201