Investigation of the Vortex State of Type-II Superconductors by Means of AN Atomic Beam.

Samuel Dapore-Schwartz

Truman R. Brown, John Gordon King

Harshwardhan Chaturvedi, Hiba Assi, Ulrich Dobramysl +2 more

Abstract We investigate the relaxation dynamics of magnetic vortex lines in type-II superconductors following rapid changes of the external driving current by means of an elastic line model simulated with Langevin molecular dynamics. A system of flux vortices in a sample with randomly distributed point-like defects is subjected to an external current of appropriate strength for a sufficient period of time so as to be in a moving non-equilibrium steady state. The current is then instantaneously lowered to a value that pertains to either the moving or pinned regime. The ensuing relaxation of the flux lines is studied via one-time observables such as their mean velocity and radius of gyration. We have in addition measured the two-time flux line height autocorrelation function to investigate dynamical scaling and aging behavior in the system, which in particular emerge after quenches into the glassy pinned state.

Voicu Dolocan

David Reginald Tilley, John Tilley

In superconductors, as in Helium II (He II), the holes round which quantisation occurs can be either physical boundaries, or the cores of quantised vortex lines. For convenience we summarise here the resemblances and differences between vortex lines and vortex states in He II and in superconductors. In contrast, states in which a whole vortex is attached to the wire should be comparatively stable. The rotation of the superfluid can be satisfactorily explained by assuming that it is threaded by a series of parallel straight vortex lines. Consider a single straight vortex line in the superfluid. The energy associated with a single vortex line is mainly the kinetic energy of the circulating superfluid. The number and separation of vortex lines present for a given angular velocity clearly depends on their individual circulations. Two rival models for the ion-vortex transition have been proposed, generally known as the peeling model and the quantum transition model.

Harry Kojima, W. Veith, Seth Putterman +2 more

Evidence is presented that below a rather large angular velocity, ${\ensuremath{\omega}}_{c1}$, there is a vortex-free state in rotating locked helium, which we call the Landau state. This is similar to the Meissner state in superconductors. We further show that all the properties of the rotating helium have counterparts in irreversible type-II superconductors and find that ${\ensuremath{\omega}}_{c2}$ (analogous to ${H}_{c2}$) greatly exceeds our high speeds of rotation.