Superconducting phase transition of artificial wire networks
This dissertation describes a study of the magnetic field dependence of the superconducting phase transition of artificial square wire networks of aluminum fabricated using electron beam lithography. The smallest loop structures were 1.7[mu]m on a side and the full length of a side of an array was up to 1mm. Two aspects of the superconducting phase transition studied were the localization of the order parameter and the superconducting glass. The Ginzburg-Landau mean field theory was the basis of theoretical considerations with the so-called London loop method used as a quick and effective tool to reveal the ground state configurations that are tied to the properties at the phase transition. Experiments were carried out investigating the effect of disorder on the phase transition by randomly removing bonds in the networks. The existence of a localized order parameter phase predicted by Soukoulis, Grest and Li was demonstrated. This result is surprising in that if a small number of bonds were removed from the network, perhaps as small as 2%, in the presence of an applied magnetic field not corresponding to integer number of flux quanta per unit cell, all the solutions to the Ginzberg-Landau equations are localized. Also studied was the effect of frustration on the superconducting phase transition by applying a magnetic field corresponding to a flux lattice which was incommensurate with that of the network. The method used to study the phase transition in this instance involved the use of the scaling analysis of current-voltage characteristics, employed by Koch et al to explore the vortex-glass phase transition in high transition temperature superconducting films. Wire networks exhibited scaling behavior, but only at certain special irrational frustration indices such as the inverse of the golden mean and [radical]2-1, indicating a continuous phase transition, possibly into a superconducting glass phase.
- Research Organization:
- Minnesota Univ., Minneapolis, MN (United States)
- OSTI ID:
- 7182658
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
360102 -- Metals & Alloys-- Structure & Phase Studies
360107* -- Metals & Alloys-- Superconducting Properties-- (1992-)
665411 -- Basic Superconductivity Studies-- (1992-)
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ALUMINIUM
DEPOSITION
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
ELEMENTS
ENERGY BEAM DEPOSITION
EQUATIONS
GINZBURG-LANDAU THEORY
LONDON EQUATION
MAGNETIC FIELDS
METALS
PHASE TRANSFORMATIONS
PHYSICAL PROPERTIES
SUPERCONDUCTING WIRES
SUPERCONDUCTIVITY
SURFACE COATING
WIRES