193 research outputs found
Enhancing the Critical Current of a Superconducting Film in a Wide Range of Magnetic Fields with a Conformal Array of Nanoscale Holes
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.Comment: 5 pages, 3 figure
Charge density wave and superconductivity competition in LuIrSi : a proton irradiation study
Real-space modulated Charge Density Waves (CDW) are an ubiquituous feature in
many families of superconductors. In particular, how CDW relates to
superconductivity is an active and open question that has recently gathered
much interest since CDWs have been discovered in many cuprates superconductors.
Here we show that disorder induced by proton irradiation is a full-fledged
tuning parameter that can bring essential information to answer this question
as it affects CDW and superconductivity with different and unequivocal
mechanisms. Specifically, in the model CDW superconductor LuIrSi
that develops a 1D CDW below 77\,K and s-wave superconductivity below 4\,K, we
show that disorder enhances the superconducting critical temperature
and while it suppresses the CDW. Discussing how
disorder affects both superconductivity and the CDW, we make a compelling case
that superconductivity and CDW are competing for electronic density of states
at the Fermi level in LuIrSi, and we reconcile the results
obtained via the more common tuning parameters of pressure and doping. Owing to
its prototypical, 1D, Peierls type CDW and the s-wave, weak-coupling nature of
its superconductivity, this irradiation study of LuIrSi provides
the basis to understand and extend such studies to the more complex cases of
density waves and superconductivity coexistence in heavy fermions, Fe-based or
cuprates superconductors.Comment: 25 pages single column, 4 figures in main text + 3 figures in
appendi
Nanocalorimetric Evidence for Nematic Superconductivity in the Doped Topological Insulator SrBiSe
Spontaneous rotational-symmetry breaking in the superconducting state of
doped has attracted significant attention as an
indicator for topological superconductivity. In this paper, high-resolution
calorimetry of the single-crystal
provides unequivocal evidence of a two-fold rotational symmetry in the
superconducting gap by a \emph{bulk thermodynamic} probe, a fingerprint of
nematic superconductivity. The extremely small specific heat anomaly resolved
with our high-sensitivity technique is consistent with the material's low
carrier concentration proving bulk superconductivity. The large basal-plane
anisotropy of is attributed to a nematic phase of a two-component
topological gap structure and caused by a
symmetry-breaking energy term .
A quantitative analysis of our data excludes more conventional sources of this
two-fold anisotropy and provides the first estimate for the symmetry-breaking
strength , a value that points to an onset transition of
the second order parameter component below 2K
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