Observation of the superconducting proximity effect from kinetic-inductance measurements

Journal Article · Fri Nov 01 04:00:00 EST 1991 · Physical Review, B: Condensed Matter; (United States)

DOI:https://doi.org/10.1103/PhysRevB.44.9605· OSTI ID:6001188

Claassen, J H ^[1]; Evetts, J E; Somekh, R E; Barber, Z H ^[2]

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1. Naval Research Laboratory, Washington, D.C. (USA)
2. University of Cambridge, Cambridge CB2 3QZ (United Kingdom)

A method is described for observing the proximity effect in a thin-film-superconductor--normal-metal bilayer. The superconducting film must be thin compared to its penetration depth. The kinetic inductance of the superconducting film alone is then proportional to {lambda}{sup 2}({ital T})/{ital d}. It is found that in a bilayer the temperature dependence of the kinetic inductance deviates significantly from this dependence at low temperatures. The kinetic inductance may be measured in a nondestructive manner using the two-coil mutual-inductance technique. Bilayers of NbN/Al and Nb/Cu have both exhibited the effect, whereas a bilayer in which the proximity coupling was purposefully suppressed had the same temperature dependence as the superconducting film alone. The effect is analyzed in terms of a spatially varying penetration depth through the film thickness, and the observations are found to be in qualitative agreement with the predictions of the model. A more exact fitting will require improved theoretical models for the proximity effect.

• OSTI ID: 6001188
• Journal Information: Physical Review, B: Condensed Matter; (United States), Journal Name: Physical Review, B: Condensed Matter; (United States) Vol. 44:17; ISSN PRBMD; ISSN 0163-1829
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360104* -- Metals & Alloys-- Physical Properties
360204 -- Ceramics
Cermets
& Refractories-- Physical Properties
665411 -- Basic Superconductivity Studies-- (1992-)
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ALUMINIUM
CIRCUIT THEORY
COPPER
ELECTRIC CONTACTS
ELECTRICAL EQUIPMENT
ELEMENTS
EQUIPMENT
FILMS
LAYERS
METALS
NIOBIUM
NIOBIUM COMPOUNDS
NIOBIUM NITRIDES
NITRIDES
NITROGEN COMPOUNDS
PENETRATION DEPTH
PNICTIDES
PROXIMITY EFFECT
REFRACTORY METAL COMPOUNDS
SUPERCONDUCTING FILMS
TEMPERATURE DEPENDENCE
TRANSITION ELEMENT COMPOUNDS
TRANSITION ELEMENTS