Granular superconductors and their intrinsic and extrinsic surface impedance

Journal Article · Fri Dec 01 04:00:00 EST 1995 · Journal of Superconductivity

DOI:https://doi.org/10.1007/BF00727492· OSTI ID:272672

Halbritter, J ^[1]

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1. Forschungszentrum Karlsruhe (Germany)

High-frequency experiments depend sensitively on homogeneous and inhomogeneous {open_quotes}defects{close_quotes} in the normal and superconducting state. As homogeneous effects, the intrinsic scattering time is of great theoretical importance above 0.1 THz in the surface impedance Z. Of practical importance are the planar defects, {open_quotes}the weak links (WL),{close_quotes} which interrupt the rf shielding currents and thus enhance Z{sub eff}. In the superconducting state, the Josephson current j{sub cJ} crosses the WL in parallel with the normal, leakage current j{sub bl}. The latter explains the observed, finite rf residual losses R{sub res}(T{approx}0) quantitatively and as a function of material parameters, temperature T, field H, and frequency {omega} for Nb, NbN, and cuprate superconductors. With increasing field, Z deteriorates like H{sup 2} up to H{sub c1J}{approx}0.1-10 mT, JF dynamics dominates Z with hysteresis losses and reactive components. The nonlinear JF effects are enforced by thinfilm edge enhancements limiting the performance of various devices by enhanced dissipation, reactance, and flux noise. A method is presented which is able to separate electron dynamics at the WL from their strength and distribution.

• Sponsoring Organization: USDOE
• OSTI ID: 272672
• Journal Information: Journal of Superconductivity, Journal Name: Journal of Superconductivity Journal Issue: 6 Vol. 8; ISSN JOUSEH; ISSN 0896-1107
• Country of Publication: United States
• Language: English

Related Subjects

66 PHYSICS
HIGH-TC SUPERCONDUCTORS
IMPEDANCE
JOSEPHSON EFFECT
MAGNETIC FIELDS
SUPERCONDUCTORS
SURFACES
TEMPERATURE DEPENDENCE