Dynamics of superconducting vortices driven by oscillatory forces in the plastic-flow regime

Abstract

We study experimentally and theoretically, the reorganization of superconducting vortices driven by oscillatory forces near the plastic depinning transition. We show that the system can be taken to configurations that are tagged by the shaking parameters but keep no trace of the initial conditions. In experiments performed in NbSe 2 crystals, the periodic drive is induced by ac magnetic shaking fields and the overall order of the resulting configuration is determined by noninvasive ac susceptibility measurements. With a model of interacting particles driven over random landscapes, we perform molecular dynamics simulations that reveal the nature of the shaking dynamics as fluctuating states similar to those predicted for other interacting particle systems.

Memory formation and evolution of the vortex configuration associated with random organization

“…On the other hand, it has been suggested that information on dynamic disordering [44] and on the depinning transition [19] may be involved in individual voltage pulses in response to the ac drive with a rectangular pulse shape, as observed here, as well as in V t ( ) for the ordered vortex configuration in response to the dc drive. In our previous work using the same a-Mo x Ge 1−x film system, we have found the dynamic ordering phenomena of the highly disordered pinned vortex assemblies, as well as the dynamic disordering phenomena of the ordered vortex ones, by a suddenly applied dc drive [39], consistent with the prediction of numerical simulations and other more indirect experiments [44]. The transient dynamics was well described by a critical phenomenon of the plastic depinning transition [4,13,39,45], which is similar to that seen on the irreversible side of RIT.…”

“…Dynamic ordering phenomena, analogous to random organization due to the ac drive studied here, also occur in a disordered vortex system driven by a dc force [43]. On the other hand, it has been suggested that information on dynamic disordering [44] and on the depinning transition [19] may be involved in individual voltage pulses in response to the ac drive with a rectangular pulse shape, as observed here, as well as in V t ( ) for the ordered vortex configuration in response to the dc drive. In our previous work using the same a-Mo x Ge 1−x film system, we have found the dynamic ordering phenomena of the highly disordered pinned vortex assemblies, as well as the dynamic disordering phenomena of the ordered vortex ones, by a suddenly applied dc drive [39], consistent with the prediction of numerical simulations and other more indirect experiments [44].…”

Theoretical estimates of maximum fields in superconducting resonant radio frequency cavities: stability theory, disorder, and laminates

“…Even if this process is incomplete, leaving some tangle of vortex loops, it may enter a kind of limit cycle. Indeed, many periodically stressed disordered dynamical systems can enter into limit cycles at low levels of stress, with a transition to 'turbulent' aperiodic behavior at a critical threshold (colliding colloids in reversing low-Reynolds number flows [81], plasticity in vortex structures of superconductors [82][83][84], etc). It is possible that the quench of RF cavities explores precisely this kind of dynamical phase transition, separating a local hot spot from an invading front of vortices.…”

Random organization in periodically driven gliding dislocations

“…Reversible to irreversible transitions and random organization in periodically driven systems with quenched disorder have also been studied for vortices in type-II superconductors, where behavior very similar to that of the dilute colloidal suspensions occurs: the system organizes into reversible states and has divergent transient times on either side of a critical drive amplitude [8][9][10][11] . The vortices have much longer range interactions than the colloidal particles, and in the reversible state the vortices are still strongly interacting with each other, indicating that the idea of random organization can be extended beyond systems with simple contract interactions.…”