Wednesday, June 5, 2013

1306.0147 (Yong-Lei Wang et al.)

Enhancing the Critical Current of a Superconducting Film in a Wide Range
of Magnetic Fields with a Conformal Array of Nanoscale Holes

Yong-Lei Wang, M. L. Latimer, Zhi-Li Xiao, R. Divan, L. E. Ocola, G. W. Crabtree, Wai-Kwong Kwok
The maximum current (critical current) a type-II superconductor can transmit without energy loss is limited by the motion of the quantized magnetic flux penetrating into a superconductor. Introducing nanoscale holes into a superconducting film has been long pursued as a promising way to increase the critical current. So far the critical current enhancement was found to be mostly limited to low magnetic fields. Here we experimentally investigate the critical currents of superconducting films with a conformal array of nanoscale holes that have non-uniform density while preserving the local ordering. We find that the conformal array of nanoscle holes provides a more significant critical current enhancement at high magnetic fields. The better performance can be attributed to its arching effect that not only gives rise to the gradient in hole-density for pinning vortices with a wide range of densities but also prevent vortex channeling occurring in samples with a regular lattice of holes.
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