Doctoral dissertation
Phase slip phenomena and vortex dynamics in mesoscopic superconductors
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Abstract
We investigate the dynamics in one-dimensional (1D) and two dimensional (2D) mesoscopic superconductors
in an external magnetic field using the time-dependent Ginzburg-Landau equations.
We analyze the different transitions between metastable states and describe the creation of topological
defects that occur as the phase of the Ginzburg-Landau order parameter makes finite jumps:
phase slip phenomena.
We first analyze the stability and the dynamics for the phase slip phenomena starting from a
metastable state in a 1D ring. We find a stability condition relating the winding number of
the initial metastable state and the number of flux quanta penetrating the ring. We as well
study the competition between simultaneous and consecutive multiple phase slips analytically and
numerically.
In 2D, we consider flux penetration to a superconducting thin-walled cylinder. We show that in
the low field limit, the kinetics are deterministic. In the strong field limit the dynamics become
stochastic. Analytical calculation and simulations show that, in the case of a superconducting
cylinder in the presence of a constant magnetic field, simple perturbations could not result in the
creation of well defined vortex-antivortex pairs. We identify different regimes depending on the
value of the magnetic field: at low magnetic field, quasi-1D dynamics such as vortex rivers prevail,
but at high magnetic field, the sample is quenched and kinetics are similar to the Kibble-Zurek
mechanism of vortex production. Surprisingly the inhomogeneity in the cylinder reduces the level
of stochasticity because of the predominance of Kelvin-Helmholtz vortices.
Last, we investigate the possibility of a novel kind of optical pump probe spectroscopy where the
two laser pulses are focused on different areas of the sample. The response to the destruction of
the superconducting state in a large part of a mesoscopic ring is studied numerically. We evaluate
the relaxation rates of the superconducting order parameter as well as the voltage induced by the
charge imbalance and discuss the feasibility of such measurements.