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The Josephson effect is the phenomenon of current flow across two weakly coupled superconductors, separated by a very thin insulating barrier. This arrangement—two superconductors linked by a non-conducting barrier—is known as a Josephson junction; the current that crosses the barrier is the Josephson current. The terms are named after British physicist Brian David Josephson, who predicted the existence of the effect in 1962. It has important applications in quantum-mechanical circuits, such as SQUIDs.
The basic equations  governing the dynamics of the Josephson effect are
where and are the voltage and current across the Josephson junction, is the "phase difference" across the junction (i.e., the difference in phase factor, or equivalently, argument, between the Ginzburg-Landau complex order parameter of the two superconductors comprising the junction), and is a constant, the critical current of the junction. The critical current is an important phenomenological parameter of the device that can be affected by temperature as well as by an applied magnetic field. The physical constant, is the magnetic flux quantum, the inverse of which is the Josephson constant.
The three main effects predicted by Josephson follow from these relations:
The Josephson effect has found wide usage, for example in the following areas:
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Josephson_effect". A list of authors is available in Wikipedia.|