Charge characteristics, fractionation basis

Much of the interest in superconductor components revolves around the central issue that below a characteristic temperature, Tc, superconductors exhibit zero resistance to the flow of electricity figure 1 A). Above this temperature, the material behaves as a normal metal wherein isolated electrons (or holes) carry the charge with finite resistance. Below Tc, however, the electrons form loosely associated pairs which are responsible for all the superconducting properties. At temperatures close to Tc, only a minute fraction of the conduction electrons form the Cooper pairs (Figure IB). Under such circumstances, superconductivity is easily disrupt by heati light, and magnetic fields. Creation of weakly coupled superconductor structures such as Josephson junctions, serves to further increase the sensitivity of the superconductor components. It is this sensitivity to external stimuli that provides the basis for the preparation of a variety of superconductor-based detectors and devices. 

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