Overview of superconducting behavior

For typical superconductors Tc is in the range of a few degrees kelvin, which has made it difficult to take advantage of this extraordinary behavior in practical applications, because cooling the specimen to within a few degrees of absolute zero 

Critical temperature Tc (in kelvin), critical field Hq (in oersted), and Debye frequency (in milielectronvolts). 

The discovery of high-temperature superconductors has opened the possibility of many practical applications, but these materials are ceramics and therefore more difficult to utilize than the classical superconductors, which are typically elemental metals or simple metallic alloys. It also re-invigorated theoretical interest in superconductivity, since it seemed doubtful that the microscopic mechanisms responsible for low-temperature superconductivity could also explain its occurrence at such high temperatures. J.G. Bednorz and K.A. Muller were awarded the 1987 Nobel prize for Physics for their discovery, which has sparked an extraordinary activity. 

Critical temperature Tc (in kelvin). In several cases there is fractional occupation of the dopant atoms, denoted by x (with 0 x 1), or there are equivalent structures with two different elements, denoted by (X,Y) in such cases the value of the highest Tc is given. 

In type I superconductors, the critical field He is a function of temperature and vanishes at Tc, as shown in Fig. 8.1(e) the behavior of He with temperature is 

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Overview of superconducting behavior described well by the expression... 

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