High-Tc superconductors

Some of the above discussed precursor phenomena are also observed prior to diffusion driven phase transformations. A typical example are the conventional EM tweed images obtained in the tetragonal parent phase in high Tc superconductors and other ceramics. In a recent survey by Putnis St e of such observations it was concluded that in these cases the tweed contrast resulted from underlying microstructures fomied by symmetry changes driven by cation ordering. These symmetry changes yield a fine patchwork of twin related domains which coarsen when the transfomiation proceeds. However, in view of the diffusion driven character of the latter examples, these cases should be clearly separated from those in the field of the martensites. 

Barron, A. R., Group Ila Metal Organics as MOCVD-Precursors for High Tc Superconductors, The Strem Chemiker, XIII-1, Strem Chemicals, Newburyport, MA 01950 (1990)... 

Egami T (2005) Electron-Phonon Coupling in High-Tc Superconductors 114 267-286 Egami T (2007) Local Structure and Dynamics of Ferroelectric Solids. 124 69-88 Eisenstein O, see Clot E (2004) 113 1-36... 

This review will include both types of studies, but will not discuss in any detail optically pumped NMR of semiconductors, which has been well-reviewed [5, 11, 12,14], or other unconventional techniques for detection of NMR signals. Physics-related NMR studies of more complicated semiconductor behavior such as Kondo insulators or semiconductors and other unusual semiconducting phases, and semiconducting phases of high-Tc superconductors, while very important in physics, will be neglected here. I have deemed it of some value to provide rather extensive citation of the older as well as of the more recent literature, since many of the key concepts and approaches relevant to current studies (e.g., of nanoparticle semiconductors) can be found in the older, often lesser-known, literature. My overall aim is to provide a necessarily individual perspective on experimental and theoretical approaches to the study of semiconductors by NMR techniques that will prove useful to chemists and other scientists. 

Odier, P. Supardi, Z. De-Barros, D. Vergnieres, L. Ramirez-Castellanos, J. Gonzales-Calbet, J. M. Vallet-Regi, M. Villard, C. Peroz, Ch. Weiss, F. 2004. Spray pyrolysis for high Tc superconductor films. Supercond. Sci. Technol. 17 1303-1310. 

For importance sampling in the lattice simulation, one can use the leading part of the determinant, [real, positive]. This proposal provides a nontrivial check on analytic results at asymptotic density and can be used to extrapolate to intermediate density. Furthermore, it can be applied to condensed matter systems like High-Tc superconductors, which in general suffers from a sign problem. 

The recent discovery of high Tc superconductors means that applications of electrochemistry in this field are still in the initial phases... 

For other examples involving materials see, for example, the determination of the crystal structure of the high Tc superconductor YBa2Cus07by Huang et al. [26], and K20.Nb205 [27]. 

It has now become apparent that f-band superconductors can be understood in a normal way, like d-band ones" we have just to think about density of states, bandwidth lattice unstabilities and electron correlations to interpret it. This was clearly summarized by Smith after the discovery of superconductivity of Pa and Am. Superconductivity of Am is made by the J = 0 ground state of its six 5 f electrons as was stressed by Johansson , this could also be the case for stabilized trivalent europium metal. The importance of lattice instabilities (like in A-15 high Tc superconductors) was put forward by Fournier who showed that the very large 6T/8p slope for U was mainly due to a very targe change in the electron-phonon coupling associated with the low temperature phase transition. 

In terms of the electronic age, which includes the invention of the radio, television, calculator, and computer, it has been claimed that the discovery of high Tc superconductors has resulted in a "third electronics revolution" preceded by the transistor (1947), and the vacuum tube (1904). It now appears that we have shifted from "silicon valley" to a "copper-oxide valley" with the new discoveries in the field of high Tc superconductivity. 

With the Japanese confirmation, the world "exploded" into research activity on these high Tc superconductors. 

Flux System Application to High Tc Superconductors Considerations Ref. 

Melikhov, E. and Gershanov, Y., Percolation Model of Ceramic High-Tc Superconductors. Critical Current and Current Voltage Characteristic, Physica Cl57 431 (1989). 

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