Some remarks on the theory of SQUID structures. I. Topology of SQUID structures: A unified picture

Journal Article · Sun Jun 01 04:00:00 EDT 1980 · J. Low Temp. Phys.; (United States)

DOI:https://doi.org/10.1007/BF00114893· OSTI ID:5199254

Odehnal, M; Petricek, V

A topological analysis of different rf SQUID structures is performed. A simple unified picture of these devices is obtained by considering the topological properties of the magnetic force lines around superconducting (or resistive) SQUID structures containing one weak link. Due to the periodic collapse of the superconducting order parameter in the weak link the ''normal'' space around these structures can change its connectivity. A number of rf SQUID structures are analyzed from the point of view of simple topological homotopy theory. The rf SQUID is then viewed as a device which realize a topological switching between two different classes of simple closed loops of the magnetic force lines. This switching (through the weak superconductivity region) is modulated by the low-frequency closed loops of the magnetic field and results in the well-known periodic response of the rf SQUID. The surfaces surrounding the rf excitation coil of the rf SQUID are analyzed from the point of view of homology theory. The screening currents flowing on these surfaces are represented as one-dimensional closed loops (cycles). It is shown that the SQUID can work only if the surface of the structure has at least one class of so-called nonbounding cycles, which are all ''cut'' by the weak link. A number of known SQUID structures are analyzed from the point of view of homotopy and homology theory and some new SQUID structures are discussed.

• Research Organization: Institute of Physics, Czechoslovak Academy of Sciences, Prague, Czechoslovakia
• OSTI ID: 5199254
• Journal Information: J. Low Temp. Phys.; (United States), Journal Name: J. Low Temp. Phys.; (United States) Vol. 39:5; ISSN JLTPA
• Country of Publication: United States
• Language: English

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71 CLASSICAL AND QUANTUM MECHANICS
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MEASURING INSTRUMENTS
MICROWAVE EQUIPMENT
RF SYSTEMS
SQUID DEVICES
SUPERCONDUCTING DEVICES
TOPOLOGY