High-Temperature Superconductors
The discovery by J. G. Bednorz and K. A. Müller in 1986 that the superconducting state can exist in oxides at temperatures above 30 K stimulated research in the field of superconductivity and opened a new field of research. Within a few years a large numb
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High-Temper 52. High-Temperature Superconductors
After the successful development of helium liquefaction techniques in the laboratory of Heike Kammerlingh Onnes at the University of Leiden, temperatures down to about 1 K became accessible for further research [52.1]. One of the first aspects to be studied was the electrical resistivity of pure metals at very low temperatures. The nearly temperature-independent residual resistivity of platinum and gold was found to decrease with increasing purity of the metals. In 1911 Kammerlingh Onnes found that, in contrast to the behaviour of platinum and gold, the electrical resistivity of mercury drops to an unmeasurably small value at
52.1
The Superconducting State ................... 1195 52.1.1 Characteristic Properties of Superconductors ................... 1195 52.1.2 Superconductor Electrodynamics . 1197 52.1.3 Superconductivity: A Macroscopic Quantum Phenomenon .............. 1198 52.1.4 Type II Superconductors ............. 1200
52.2 Cuprate High-Tc Superconductors: An Overview ........................................ 1202 52.2.1 Major Families of Cuprate Superconductors ........ 1202 52.2.2 Generic Phase Diagram of Cuprate Superconductors ........ 1202 52.2.3 Crystal Structures....................... 1204 52.2.4 Critical Temperatures ................. 1205 52.3 Physical Properties of Cuprate Superconductors .................. 1207 52.3.1 Anisotropic Superconductors....... 1207 52.3.2 Irreversibility Line ..................... 1208 52.3.3 Limitations of the Transport Critical Current .. 1209 52.4 Superconducting Films ......................... 1212 52.5 The Special Case of MgB2 ...................... 1214 52.6 Summary ............................................ 1216 References .................................................. 1216 terised by a transition temperature as high as 39 K, has been included in the present chapter (Sect. 52.5).
a temperature of 4.2 K, as shown in Fig. 52.1. The remarkable phenomenon of superconductivity had been discovered [52.1]. In addition to zero resistance, the superconducting state is characterised by perfect diamagnetism. W. Meissner and R. Ochsenfeld found in 1933 that, as soon as the superconducting state is reached, a magnetic field is expelled from the interior of a superconductor cooled in the presence of a static magnetic field [52.2]. In contrast to the shielding of a magnetic field applied to a material in the superconducting state, field expulsion cannot be explained by perfect conductivity. This Meissner effect
Part E 52
The discovery by J. G. Bednorz and K. A. Müller in 1986 that the superconducting state can exist in oxides at temperatures above 30 K stimulated research in the field of superconductivity and opened a new field of research. Within a few years a large number of cuprate superconductors with transition temperatures well above the boiling point of liquid nitrogen have been found. In this chapter an overview of the major families of high-temperature superconductors and their physical properties is presente
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