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Superconductivity

E-BookEPUB2 - DRM Adobe / EPUBE-Book
496 Seiten
Englisch
Wiley-VCHerschienen am24.09.20153. Auflage
The third edition of this proven text has been developed further in both scope and scale to reflect the potential for superconductivity in power engineering to increase efficiency in electricity transmission or engines.
The landmark reference remains a comprehensive introduction to the field, covering every aspect from fundamentals to applications, and presenting the latest developments in organic superconductors, superconducting interfaces, quantum coherence, and applications in medicine and industry.
Due to its precise language and numerous explanatory illustrations, it is suitable as an introductory textbook, with the level rising smoothly from chapter to chapter, such that readers can build on their newly acquired knowledge.
The authors cover basic properties of superconductors and discuss stability and different material groups with reference to the latest and most promising applications, devoting the last third of the book to applications in power engineering, medicine, and low temperature physics. An extensive list of more than 350 references provides an overview of the most important publications on the topic.
A unique and essential guide for students in physics and engineering, as well as a reference for more advanced researchers and young professionals.

Reinhold Kleiner is professor for experimental solid-state physics at the University of Tübingen, Germany. He studied physics at the Technical University of Munich, and received his PhD with a thesis on high temperature superconductors. After spending two years at the University of California at Berkeley, he returned to Germany. His research interests include superconductivity and magnetism.
Werner Buckel (1920-2003) was Professor at the Technical University of Karlsruhe and established the Institute for Superconductivity at the Research Center in Juelich. Among other honorary positions, Professor Buckel was president of the German Physical Society and the European Physical Society and was a member of the Heidelberg Academy of the Sciences and the Leibnitz Society, Berlin.mehr
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Produkt

KlappentextThe third edition of this proven text has been developed further in both scope and scale to reflect the potential for superconductivity in power engineering to increase efficiency in electricity transmission or engines.
The landmark reference remains a comprehensive introduction to the field, covering every aspect from fundamentals to applications, and presenting the latest developments in organic superconductors, superconducting interfaces, quantum coherence, and applications in medicine and industry.
Due to its precise language and numerous explanatory illustrations, it is suitable as an introductory textbook, with the level rising smoothly from chapter to chapter, such that readers can build on their newly acquired knowledge.
The authors cover basic properties of superconductors and discuss stability and different material groups with reference to the latest and most promising applications, devoting the last third of the book to applications in power engineering, medicine, and low temperature physics. An extensive list of more than 350 references provides an overview of the most important publications on the topic.
A unique and essential guide for students in physics and engineering, as well as a reference for more advanced researchers and young professionals.

Reinhold Kleiner is professor for experimental solid-state physics at the University of Tübingen, Germany. He studied physics at the Technical University of Munich, and received his PhD with a thesis on high temperature superconductors. After spending two years at the University of California at Berkeley, he returned to Germany. His research interests include superconductivity and magnetism.
Werner Buckel (1920-2003) was Professor at the Technical University of Karlsruhe and established the Institute for Superconductivity at the Research Center in Juelich. Among other honorary positions, Professor Buckel was president of the German Physical Society and the European Physical Society and was a member of the Heidelberg Academy of the Sciences and the Leibnitz Society, Berlin.
Details
Weitere ISBN/GTIN9783527686544
ProduktartE-Book
EinbandartE-Book
FormatEPUB
Format Hinweis2 - DRM Adobe / EPUB
FormatFormat mit automatischem Seitenumbruch (reflowable)
Verlag
Erscheinungsjahr2015
Erscheinungsdatum24.09.2015
Auflage3. Auflage
Seiten496 Seiten
SpracheEnglisch
Dateigrösse23185 Kbytes
Artikel-Nr.3220457
Rubriken
Genre9201

Inhalt/Kritik

Leseprobe
Introduction

In physics, many phenomena result from the activity of specific mutual interactions. An important example is the relation between the uncorrelated thermal motion of the atomic building blocks of matter and the ordering forces between these building blocks. With increasing temperature, the thermal motional energy eventually becomes sufficiently large compared to some relevant ordering interaction energy that the ordered state of matter, established at low temperatures, breaks down. All phase transitions, say, from the liquid to the gaseous state, as well as the construction of the atoms themselves from the elementary constituents of matter, follow this rule. Therefore, it is not surprising that often unexpected new properties of matter, which subsequently also may become important for technology, are discovered in experiments performed under extreme conditions. Superconductivity is an example of such a discovery.

In the year 1908, Kamerlingh-Onnes [1],1 Director of the Low-Temperature Laboratory at the University of Leiden, finally achieved the liquefaction of helium as the last of the noble gases. He had founded this laboratory, which became world-famous under his leadership. At atmospheric pressure the boiling point of helium is 4.2 K. It can be reduced further by pumping. The liquefaction of helium extended the available temperature range near to the absolute zero point. The first successful experiment still needed the total combined manpower of the Institute. However, earlier Kamerlingh-Onnes was able to perform extended experiments at these low temperatures. At first, he started an investigation of the electrical resistance of metals.

At that time, ideas about the mechanism of electrical conduction were only poorly developed. It was known that it must be electrons affecting the charge transport. Also the temperature dependence of the electrical resistance of many metals had been measured, and it had been found that near room temperature the resistance decreases linearly with decreasing temperature. However, at low temperatures, this decrease was found to become weaker and weaker. In principle, there were three possibilities to be discussed:
The resistance could approach zero value with decreasing temperature (James Dewar, 1904; Figure 1, curve 1).
It could approach a finite limiting value (Heinrich Friedrich Ludwig Matthiesen, 1864; Figure 1, curve 2).
It could pass through a minimum and approach infinity at very low temperatures (William Thomson = Lord Kelvin, 1902; Figure 1, curve 3).

Figure 1 Schematics of the temperature dependence of electrical resistance at low temperatures. See text for details of curves.

In particular, the third possibility was favored by the idea that at sufficiently low temperatures, the electrons are likely to be bound to their respective atoms. Hence, their free mobility was expected to vanish. The first possibility, according to which the resistance would approach zero at very low temperatures, was suggested by the strong decrease with decreasing temperature.

Initially, Kamerlingh-Onnes studied platinum and gold samples, since at that time he could obtain these metals with high purity. He found that during the approach to zero temperature, the electrical resistance of his samples reached a finite limiting value, the so-called residual resistance, a behavior corresponding to the second possibility discussed earlier. The value of this residual resistance depended on the purity of the samples. The purer the samples, the smaller was the residual resistance. After these results, Kamerlingh-Onnes expected that in the temperature range of liquid helium ideally pure platinum or gold should have a vanishingly small resistance. In a lecture at the Third International Congress of Refrigeration in Chicago in 1913, he reported on these experiments and arguments. There he said [2]: Allowing a correction for the additive resistance I came to the conclusion that probably the resistance of absolutely pure platinum would have vanished at the boiling point of helium. These ideas were supported further by the quantum physics rapidly developing at that time. Albert Einstein had proposed a model of crystals, according to which the vibrational energy of the crystal atoms should decrease exponentially at very low temperatures. Since the resistance of highly pure samples, according to the view of Kamerlingh-Onnes (which turned out to be perfectly correct, as we know today), is only due to this motion of the atoms, his hypothesis mentioned above appeared obvious.

In order to test these ideas, Kamerlingh-Onnes decided to study mercury, the only metal at the time that he hoped could be extremely well purified by means of multiple distillation. He estimated that at the boiling point of helium he could barely just detect the resistance of mercury with his equipment, and that at still lower temperatures it should rapidly approach a zero value.

The initial experiments carried out by Kamerlingh-Onnes, together with his coworkers Gerrit Flim, Gilles Holst, and Gerrit Dorsman, appeared to confirm these concepts. At temperatures below 4.2 K the resistance of mercury, indeed, became immeasurably small. In his lecture of 1913, Kamerlingh-Onnes summarized this phase of his experiments and ideas as follows: With this beautiful prospect before me there was no more question of reckoning with difficulties. They were overcome and the result of the experiment was as convincing as could be.

However, during his further experiments using improved apparatus, he soon recognized that the observed effect could not be identical to the expected decrease in resistance. The resistance change took place within a temperature interval of only a few hundredths of a degree and, hence, it resembled more of a resistance jump than a continuous decrease.

Figure 2 shows the curve published by Kamerlingh-Onnes [3]. As he himself commented [2]: At this point (slightly below 4.2 K) within some hundredths of a degree came a sudden fall not foreseen by the vibrator theory of resistance, bringing the resistance at once to less than a millionth of its original value at the melting point. ⦠Mercury had passed into a new state, which on account of its extraordinary electrical properties may be called the superconductive state.

Figure 2 The superconductivity of mercury.

(After Ref. [3].)

In this way, also the name for this new phenomenon had been found. The discovery came unexpectedly during experiments that were meant to test some well-founded ideas. Soon it became clear that the purity of the samples was unimportant for the vanishing of the resistance. The carefully performed experiment had uncovered a new state of matter.

Today we know that superconductivity represents a widespread phenomenon. In the Periodic Table of the elements, superconductivity occurs in many metals. Here, at atmospheric pressure, niobium is the element with the highest transition temperature of about 9 K. Thousands of superconducting compounds have been found, and this development is by no means closed.

The scientific importance of the discovery of superconductivity can be seen from the fact that in 1913 Kamerlingh-Onnes was awarded the Nobel Prize in physics. At that time, hardly anybody could have foreseen the richness in fundamental questions and interesting concepts resulting from this observation, and it took nearly half a century until superconductivity was understood at least in principle.2

The vanishing of the electrical resistance below a critical temperature or transition temperature Tc is not the only unusual property of superconductors. An externally applied magnetic field can be expelled from the interior of super-conductors except for a thin outer layer ( ideal diamagnetism or Meissner-Ochsenfeld effect ), or superconductors can concentrate the magnetic field in the form of flux tubes. Here, the magnetic flux is quantized3 in units of the magnetic flux quantum, Φ0 = 2.07 × 10â15 Wb. The ideal diamagnetism of superconductors was discovered by Walther Meissner and Robert Ochsenfeld in 1933. It was a big surprise, since based on the induction law one would only have expected that an ideal conductor conserves its interior magnetic field and does not expel it.

The breakthrough in the theoretical understanding of superconductivity was achieved in 1957 by the theory of John Bardeen, Leon Neil Cooper, and John Robert Schrieffer ( BCS theory ) [4]. In 1972, they were awarded the Nobel Prize in physics for their theory. They recognized that at the transition to the superconducting state the electrons condense pairwise into a new state, in which they form a coherent matter wave with a well-defined phase, following the rules of quantum mechanics. Here the interaction of the electrons is mediated by the phonons, the quantized vibrations of the crystal lattice.

The formation of a coherent matter wave, often referred to as a macroscopic wave function, represents the key property of the superconducting state. We know similar phenomena from other branches of physics. The laser is based on a coherent wave represented by photons. In the phenomenon of superfluidity below the so-called lambda point, the helium atoms condense into a coherent matter wave [5, 6]. For the isotope 4He the lambda point is 2.17 K, and for 3He it is...
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