High Tc superconducting

In refs (Kim,2004 Kim, 2005) we take one step further estimating corrections to the Gaussian effective potential for the U(l) scalar electrodynamics where it represents the standard static GL effective model of superconductivity. Although it was found that, in the covariant pure (f)4 theory in 3 + 1 dimensions,corrections to the GEP are not large (Stancu,1990), we do not expect them to be negligible in three dimensions for high Tc superconductivity, where the system is strongly correlated. 

All the above numerical calculations were made in D=3 dimension. On the other hand it is widely known that, most of high Tc cuprates have layered structures with 2D CuO2 planes which play an essential role in the high Tc superconductivity.Therefore, it is nessesary to consider the dimensional contribution in the calculation.For this purpose,we consider the case of D = 2 + 2e (e / 0) in the post Gaussian approximation.In this case the optimal values of m and A also depend on e. Using Eq.(25) and the procedure outlined above one finds the e dependence of m2 presented in Fig.3 (solid line). 

For e > 0.1,there is a possibility to adjust e to the recent experimental data on k(T) (Brandstatter,1994) for high — Tc cuprate superconductor TI2CC12(7 — 2223). Our calculations show that,the best choice of e is found to be e = 0.21.The appropriate k(t) is presented in Fig.4 (solid line). The dashed line in this figure shows k(t) for D = 3. This fitting process allows us to get an estimation on the effective dimensionality of the high — Tc superconducting materials. 

After more than ten years of extensive experimental and theoretical studies of the phenomenon of the high Tc superconductivity (HTSC) [1], we still do not know a microscopic mechanism responsible for this phenomenon. Numerous theories of pairing, which lead to high Tc values, are based on models [2-9] and cannot connect a specific chemical composition of HTSC ceramics with the value of the transition temperature Tc. For creating a quantitative theory of the HTSC phenomenon further comparative studies of the electronic structure and their relative properties of SC and non-SC ceramics are needed. In this paper, we confine ourselves to calculations of the electronic structure of the SC yttrium ceramics. 

E. Kaldis et al. (eds) High - Tc superconductivity 1996 Ten Years after the Discovery, Klumer Acad. Publ., the Netherlands, (1997)... 

A.S. Alexandrov and N.F. Mott High Tc Superconductivity and Other Superfluids, Taylor, London 1994 Polarons andBipolarons, World Scientific, Singapore, (1995)... 

The electron density in transition metal complexes is of unusual interest. The chemistry of transition metal compounds is of relevance for catalysis, for solid-state properties, and for a large number of key biological processes. The importance of transition-metal-based materials needs no further mention after the discovery of the high-Tc superconducting cuprates, the properties of which depend critically on the electronic structure in the CuOz planes. 

The re arch in catalysis is still one of the driving forces for interface science. One can certainly add to the topics of interface physics the whole new field of interface problems that is about to spring out of the new high Tc superconducting ceramics, i.e. the fundamental problem of the matching of the superconducting carriers wave-functions with the normal state metal or semiconductor electron states, the super-conductor-superconductor interfaces and so on, as well as the wide open discovery field for devices and applications. 

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. 

Paul" Chu, and others at University of Houston, also reproduced Zurich s I.B.M. research results (156). Bell Lab s confirmation of Bednorz and Muller s discovery of high Tc superconductivity in copper oxide compounds was published (157) in the Jan. 1987 issue of Physical Review Letters. The electrical resistivity data from their work showing an onset of superconductivity at 36.5 K for the composition Lax gSr0 2Cu04 is plotted as Figure 28. This product also showed a 60-70% Meissner effect. 

With the discovery and disclosure of these events in the area of "High Tc Superconductivity", hundreds, if not thousands, of scientists actively became involved in research on these new materials. Newer materials and higher Tc s soon followed. The competition was fierce and the progress through 1987 and 1988 was moving at a rapid pace with numerous important discoveries. To date, the highest Tc is in the range of 110-125 K, some five times that obtained in 1973 on the revolutionary (A-15) intermetallic materials. These new copper -oxide systems, many of which will be described in detail by other contributors to this book, are presented in Table 10. 

Many of these substitutions were carried out in Japan and in the U.S. immediately after the disclosure of high Tc superconductivity in the barium-doped La2Cu04 samples. 

Shoji Tanaka, "Research on High-Tc Superconductivity in Japan", Physics Today, 53-57 December (1987). 

The lack of homogeneity pervades most of the systems where high Tc superconductivity has been observed. The n-type copper oxides, e.g., Nd2 xCexCu04 and Nd2Cu04 xFx are particularly plagued with this problem because superconductivity exists over such a small range of x. The inevitable variations of x on a microscopic level will inevitably lead to materials which are not electronically homogeneous. 

D. Mihailovic, and K.A. Muller, in Materials Aspects of High-Tc Superconductivity, NATOASI, Kluwer, Dordrecht, 1 (1997). 

In this paper, we investigate our two-band model for the explanation the multi-gap superconductivity of MgB2. We apply the model to an electron-phonon mechanism for the traditional BCS method, an electron-electron interaction mechanism for high- Tc superconductivity, and a cooperative mechanism in relation to multi-band superconductivity. 

J. Rohler, P. W. Loeffen, S. Mullender, K. Conder, and E. Kaldis in Workshop on High-Tc Superconductivity 1996 Ten Years after the Discovery, eds. E. Kaldis, E. Liarokapis, and K.A. Muller, (NATO ASI Series, Kluwer Academic Publishers,... 

K. A. Muller, G.-M. Zhao, K. Conder and H. Keller Journal of Physics Condensed Matter IIS, L291-L296 (1998) D. Mihailovic andK. A. Muller in High-Tc Superconductivity 1996 Ten Years after the Discovery", edited by E. Kaldis, E. Liarokapis and K. A. Muller (Kluwer Academic, Dordrecht 1996) NATO ASI Series vol. 343 pp. 243. 

Further, if the model is correct then artificial structures with nanolayers of metal and AFM insulator to model high- Tc superconductivity in the Cu02 layer (fig.4) can be studied. Of course, such a structure is a 3D object... 

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