TABLE OF CONTENTS We have hitherto discussed how important and interesting the phenomenon of superconductivity is. We hope that the reader has already realized the importance of this phenomenon and is now eagerly awaiting the answer to the question of why has superconductivity aroused so much interest of late? Before 1986, the situation was quite different. The discussion of superconductivity did not attain the level of practical usage outside the realms of physics research. It was mentioned in popular scientific and fantasy books rather as something exotic and not frequently encountered in our everyday life. Most people had not even heard of this phenomenon. Other more effective technical applications of physical discoveries, for example, atomic bomb, lasers, and semiconductor electronics, overshadowed superconductivity. But now it has reached a turning point.
The new era began in October 1986, when G.Bednorz and K.M ller published their paper concerning a possible observation of superconductivity at a temperature above 30 K. The authors were very cautious: reports of an increase in the critical temperature had appeared but had never been confirmed. This time the result was not only confirmed but very soon improved . In early 1987, it was established in several laboratories that in some compounds containing the four chemical elements lanthanum, strontium, copper, and oxygen (La-Sr-Cu-O), a sufficiently sharp superconducting transition was observed at T c=36 K. This fact alone was enough to excite the world of physics. In March 1987, a report on superconductivity in compounds of yttrium, barium, copper, and oxygen...
