arXiv subjects

Sung Hun Wee

Publications and source records attributed to Sung Hun Wee.

2 recordsLinked to original sources

arXiv2011

Transition from columnar to point pinning in coated conductors: critical currents, that are independent of magnetic field direction

We identify a phase transition in the vortex system of a high-temperature superconductor with nano-columnar stacks of precipitates as strong vortex pinning centers. Above a particular, temperature-dependent field $B_X(T)$ the vortex response is no longer determined by the nano-columns, and is instead determined by point-like pinning. This phase transition leads to the change in the measured critical current density as a function of angle between the applied magnetic field and the nano-columns. Below the unbinding, there is a strong maximum in $J_C$ when field is aligned parallel to the columns. Above the unbinding, there is a minimum for this orientation.

cond-mat.supr-con↗

arXiv2008

Tuning flux-pinning in epitaxial NdBa2Cu3O7-x films via engineered, hybrid nanoscale defect structures

Epitaxial NdBa2Cu3O7-x films with a hybrid nanoscale defect structure comprised of BaZrO3 nanodot arrays aligned along the c-axis in one half of the film thickness and aligned perpendicular to the c-axis in the other half thickness of the film were fabricated. Transmission electron microscopy images confirm the orientation of the nanoscale defect structures. The angular dependence of critical current density, Jc, at 77 K, 1 T, shows significantly reduced angular variation of Jc. This study nicely demonstrates how pinning characteristics can be tuned by tuning the nanoscale defect structures within the films.

cond-mat.supr-con↗