Preface

Superconductivity is a fascinating field of the solid state physics. For more than four decades since the discovery in 1911 of the first superconductor, Hg, by Heike Kamerlingh Onnes its origin was unclear. This uncommon situation was changed by the appearance of the Cooper pair concept and the creation in 1957 of the Bardeen-Cooper-Schrieffer (BCS) theory of superconductivity. Subsequent years were full of other significant discoveries in this area so that now one can consider superconductivity as the scientific industry with plenty of applications as well as the testing ground for new theories and investigation methods. Number of books devoted to the phenomenon concerned, superconducting materials and devices is enormous. A question arises: why do we need more textbooks and monographs?

The answer consists in extremely rapid progress of the materials science quickly making preceding volumes obsolete. Moreover, new ideas emerge stimulated by novel materials and the intrinsic logic of the developing theoretical physics. Note, that the branches of the latter are interconnected so that, e.g., the field theory and the condensed matter physics help one another inventing sophisticated tools and bold concepts. At the same time, the experimental capabilities even of well-known methods, such as photoemission ones, steadily expand making possible to study microscopic details of the superconducting energy gap structures or magnetic vortex patterns. Thus, the represented book is an attempt (we hope, a successful one) to describe most recent events in this field.

The book includes 17 chapters written by noted scientists and young researchers and dealing with various aspects of superconductivity, both theoretical and experimental. The authors tried to demonstrate their original vision and give an insight into the examined problems. A balance between theory and experiment was preserved at least from the formal viewpoint (9 and 8, respectively). I am not going to describe each of the chapters because "*the proof of the pudding is in the eating*". Nevertheless, it is my duty to warn the readers that many of the problems studied here are far from being solved. In particular, it concerns my favorite pseudogap concept. It is investigated in several chapters with quite different conclusions. The reason is that such is the state of the art!

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I hope the book will be useful for undergraduates, postgraduates and professionals as a collection of important results and deep thoughts in the vast field of superconductivity.
