87 research outputs found
Electronic state around vortex in a two-band superconductor
Based on the quasiclassical theory, we investigate the vortex state in a
two-band superconductor with a small gap on a three dimensional Fermi surface
and a large gap on a quasi-two dimensional one, as in MgB_2. The field
dependence of zero-energy density of states is compared for fields parallel and
perpendicular to the ab plane, and the anisotropy of the vortex core shape is
discussed for a parallel field. The Fermi surface geometry of two-bands,
combining the effect of the normal-like electronic state on the small gap band
at high fields, produces characteristic behavior in the anisotropy of c- and
ab-directions.Comment: 6 pages, 6 figures, to appear in Phys. Rev.
Ambegaokar-Baratoff relations of Josephson critical current in heterojunctions with multi-gap superconductors
An extension of the Ambegaokar-Baratoff relation to a
superconductor-insulator-superconductor (SIS) Josephson junction with multiple
tunneling channels is derived. Appling the resultant relation to a SIS
Josephson junction formed by an iron-based (five-band) and a single-band
Bardeen-Cooper-Schrieffer (BCS) type superconductors, a theoretical bound of
the Josephson critical current () multiplied by the resistance of
the junction () is given. We reveal that such a bound is useful for
identifying the pairing symmetry of iron-pnictide superconductors. One finds
that if a measured value of is smaller than the bound then
the symmetry is -wave, and otherwise -wave without any sign changes.
In addition, we stress that temperature dependence of is
sensitive to the difference of the gap functions from the BCS type gap formula
in the above heterojunction.Comment: 7 pages, 6 figure
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