Relaxation dynamics of vortex lines in disordered type-II superconductors following magnetic field and temperature quenches

Abstract

We study the effects of rapid temperature and magnetic field changes on the non-equilibrium relaxation dynamics of magnetic vortex lines in disordered type-II superconductors by employing an elastic line model and performing Langevin molecular dynamics simulations. In a previously equilibrated system, either the temperature is suddenly changed, or the magnetic field is instantaneously altered which is reflected in adding or removing flux lines to or from the system. The subsequent aging properties are investigated in samples with either randomly distributed point-like or extended columnar defects, which allows to distinguish the complex relaxation features that result from either type of pinning centers. One-time observables such as the radius of gyration and the fraction of pinned line elements are employed to characterize steady-state properties, and two-time correlation functions such as the vortex line height autocorrelations and their mean-square displacement are analyzed to study the non-linear stochastic relaxation dynamics in the aging regime.

Paramagnetic Meissner effect in ZrB12single crystal with non-monotonic vortex–vortex interactions

“…One efficient way to study a system with metastable magnetic responses is to measure the magnetic relaxation with time. This has been used to study spin dynamics [31,32], interacting magnetic nanoparticles [33,34] and superconductors [35][36][37]. In order to probe the vortex configurations in different regions of the phase diagram, we measured the magnetic relaxation across the different phase boundaries, as indicated by the crosses in figure 5(b).…”

Disordered vortex matter out of equilibrium: a Langevin molecular dynamics study

“…For our implementation of the Langevin molecular dynamics method for disordered type-II superconductors [6,[13][14][15] we also require expressions for the vortex-vortex interaction as well as for the attractive pinning potential. The repulsive in-plane vortex-vortex interaction is given by…”

Critical scaling and aging near the flux-line-depinning transition

“…In this present work, we employ an elastic line model to study critical behavior near the depinning transition for vortices in the presence of weak attractive random quenched disorder (point defects) in a three-dimensional system (d = 3) with a two-dimensional displacement vector (N = 2) [42][43][44][45][46][47] . We perform finite-temperature scaling on both steady-state velocity and radius of gyration data and thereby obtain the stationary critical scaling exponents β, δ, and ν that characterize the depinning process as a continuous second-order phase transition at zero temperature, finding β to be in good agreement with experimental values.…”