High Temperature Superconductivity

High Temperature Superconductivity

High Temperature Superconductivity I~.L Ginzburg and D.A~ Kirzhnits (eds) In this basically theoretical study of the calculation of the critical tempe...

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High Temperature Superconductivity I~.L Ginzburg and D.A~ Kirzhnits (eds) In this basically theoretical study of the calculation of the critical temperature in superconductors, the editors and other authors explore the basis for extending superconductivity into higher temperature regimes. The book was first published in Russian in 1977 and updated for this English version in 1982. As pointed out by the editors, this field is relatively slow-moving and as a result the book still provides an excellent background and literature review for present work. As with most studies in superconductivity, with the glaring exception of the Josephson effecL experimental and empirical studies have historically led the theoretical development. Thus this book provides not only the necessary background for further theoretical development but also some guidance for the experimental search for higher critical temperature superconductors. The introduction in Chapter 1 by Ginzburg is an excellent summary of the rest of the book and provides not only most of the major conclusions but also a guide where to delve into further detail in subjects of specific interest. Chapters 2 and 3 lay the groundwork in general superconductivity theory and the electronphonon interaction. The calculation of the critical temperature, Tc, for three-dimensional systems is discussed at length in Chapter 4 and covers most of the present practical superconductors. Included is an excellent discussion of the dependence of Tc on properties of the normal metal. Also explained are the reasons why an exciton mechanism for superconductivity in three-dimensional systems is not likely but also not eliminated as a possibility. In Chapter 5 it

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is shown how electronic phase transitions can lead to drastic changes in the electronic density of states and affect Tc. Also, it is shown how spontaneous currents in the material can lead to superdiamagnetism such as observed in CuCl. Chapters 6 and 7 explore two- and one-dimensional systems and the role of fluctuations and possible excitonic mechanisms. Also discussed are the typical materials studied, such as intercalated compounds and organic long-chain molecules, respectively. Discussions of dielectric-metal-dielectric sandwiches (layered compounds) and nonequilibrium superconductivity complete the book in Chapters 8 and 9. The roles of critical field and critical current are too easily dismissed by the editors as closely related to Tc and not as important. However, it is certainly not within the realm of practicality to include such developments within a single volume. Still, a discussion of the role of pinning mechanisms, for example, or the extensive empirical search for high Tc materials would have completed the picture. All the authors show a high degree of clarity in their writing and intersperse their extensive theoretical developments with lucid explanations. Such a thorough and understandable background in a book is a valuable source for those working in the field. The authors' overall conclusions are simply stated in that a limit of Tc < 300 K is probable but it would likely require an exciton mechanism in a lower-dimensional system. They also urge wide-ranging and diverse studies in many different kinds of systems, because we stand to learn a great deal about the phenomenon of superconductivity even if no high temperature superconductor is found.

ME Clark

CRYOGENICS. DECEMBER 1983