8 research outputs found
Nonlocal Effects and Shrinkage of the Vortex Core Radius in YNi2B2C Probed by muSR
The magnetic field distribution in the vortex state of YNi2B2C has been
probed by muon spin rotation (muSR). The analysis based on the London model
with nonlocal corrections shows that the vortex lattice has changed from
hexagonal to square with increasing magnetic field H. At low fields the vortex
core radius, rho_v(H), decreases with increasing H much steeper than what is
expected from the sqrt(H) behavior of the Sommerfeld constant gamma(H),
strongly suggesting that the anomaly in gamma(H) primarily arises from the
quasiparticle excitations outside the vortex cores.Comment: 4 pages, 4 figures, submitted to Phys. Rev.
Effect of electron irradiation on vortex dynamics in YBa_2Cu_3O_{7-x} single crystals
We report on drastic change of vortex dynamics with increase of quenched
disorder: for rather weak disorder we found a single vortex creep regime, which
we attribute to a Bragg-glass phase, while for enhanced disorder we found an
increase of both the depinning current and activation energy with magnetic
field, which we attribute to entangled vortex phase. We also found that
introduction of additional defects always increases the depinning current, but
it increases activation energy only for elastic vortex creep, while it
decreases activation energy for plastic vortex creep.Comment: 4 pages, 3 figures, submited to Phys. Rev.
Dynamic Vortex Phases and Pinning in Superconductors with Twin Boundaries
We investigate the pinning and driven dynamics of vortices interacting with
twin boundaries using large scale molecular dynamics simulations on samples
with near one million pinning sites. For low applied driving forces, the vortex
lattice orients itself parallel to the twin boundary and we observe the
creation of a flux gradient and vortex free region near the edges of the twin
boundary. For increasing drive, we find evidence for several distinct dynamical
flow phases which we characterize by the density of defects in the vortex
lattice, the microscopic vortex flow patterns, and orientation of the vortex
lattice. We show that these different dynamical phases can be directly related
to microscopically measurable voltage - current V(I) curves and voltage noise.
By conducting a series of simulations for various twin boundary parameters we
derive several vortex dynamic phase diagrams.Comment: 5 figures, to appear in Phys. Rev.