Superconducting system

Superconductivity has been known since 1911, and superconducting systems based on various metal alloys (e.g., NbTi and Nb3Sn) are currently used as magnets and in electronics. These materials exhibit superconductivity only at temperatures below 23 K and require cooling by liquid helium. The discovery of ceramics that exhibit superconductivity at temperatures up to 120 K, the so-called high-temperature superconductors, has sparked a tremendous amount of scientific activity and commercial interest around the world. 

In a superconducting system, when one increases the temperature at a given chemical potential, thermal motion will eventually break up the quark Cooper pairs. In the weakly interacting Bardeen-Copper-Schrieffer (BCS) theory, the transition between the superconducting and normal phases is usually of second order. The ratio of the critical temperature TcBCS to the zero temperature value of the gap AbGS is a universal value [18]... 

That our normal EM power systems do not exhibit COP> 1.0 is purely a matter of the arbitrary design of the systems. They are all designed with closed current loop circuits, which can readily be shown to apply the Lorentz symmetric regauging condition during their excitation discharge in the load. Hence all such systems — so long as the current in the loop is unitary (its charge carriers have the same m/q ratio) — can exhibit only COP< 1.0 for a system with internal losses, or COP =1.0 for a superconductive system with no internal losses. 

All four superconducting systems are metallic above their transition temperature, which agrees with the results of band structure calculations.31 34 What is, perhaps, puzzling, yet extremely useful in attempting to assess possible mechanisms for superconductivity is the observation that other compounds with similar structural features are not superconductors. In addition to LnNiBC (BC3- dimers), these include CaC2 (Cf dimers),... 

IR reflection spectra have been used to study the free carrier concentration and the free carrier lifetime in superconducting systems. As an example. Fig. 4.8-17c shows the... 

At birth, the molecular metal was the one-dimensional metal. KCP and TTF-TCNQ are typical examples. The one-dimensional metal, however, is not a metal in the low temperature region due to the instability of the planar Fermi surface. Of course, this instability has provided rich physics [3], but is not favorable to the superconductivity. Therefore, chemists made efforts to increase the dimensionality of the electronic structure by the chemical modification with great success. The first organic superconducting system, the Bechgaard salt, is a quasi-one-dimensional system [4]. BEDT-TTF salts, the second-generation organic superconductors, have typical two-dimensional Fermi surfaces [5]. Three-dimensional Fermi surface has been found in the DCNQI-Cu salt [6]. 

Blatt [36], Coleman [37, 38], then Bratoz and Durand [39] investigated a special N-electron wave function in which all geminals were constrained to have the same form, and established the relationship between this function and that used by Bardeen, Cooper and Shieffer (BCS) [40] to describe superconducting systems with electron pairs. The underlying wave function was termed as the antisymmetrized geminal power (AGP) function. 

The concerted discussion of the topics outlined above should help us advance the new paradigm that addresses our abilities to diagnose and manipulate the entangled states of complex quantum objects and their robustness against decoherence. These abilities are required for quantum information (QI) applications or matter-wave interferometry in molecular, semiconducting or superconducting systems. On the fundamental level, this book may help establish the notion of dynamical information exchange between quantum systems and chart in detail the route from unitarity to classicality. 

A. F. Marshall R. Ramesh, in Interfaces in high-Tc superconducting systems, eds. S. Shinde and D. Rudman (Springer-Verlag, New York, 1994) p. 71, and references therein. 

Suh, J. H., The effect of synthesis processes on the microstructure of Y-Ba-Cu-O superconducting system, PhD Thesis, KAIST, Daejeon, 1992. 

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