Superconducting materials cuprates

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. 

More than 15 years studies of high temperature superconductivity in cuprates accumulated many evidences of the d-wave type symmetry of the superconducting order parameter (OP) in these materials. The most strong ones has been found from the ARPES experiments [1], quantum interference... 

This raises two questions (1) are the SrO layers (or the cuprate planes) of other superconducting materials the hosts of superconductivity and (2) do Sr2YRuOe s sister compounds, GdS C RuOs andGd2- Ce Sr2Cu2RuOio, superconduct in their cuprate planes or in their SrO layers ... 

Many of the traditional methods continue to be exploited to synthesise novel materials. In the area of cuprates, the synthesis of a superconducting ladder cuprate and of car-bonato- and halocuprates is noteworthy. High pressure methods have been particularly useful in the synthesis of certain cuprates and other materials.36,44 The combustion method has come of age for the synthesis of oxidic and other materials.45 Microwave synthesis is becoming popular46 while sonochemistry has begun to be exploited.47... 

Localisation of electron den ty over a small region in a crystal lattice occupied by 02 leads to the increased importance of electron correlation which cannot be tackled by traditional one-electron or HF theories[61]. Here we build upon our previous studies in which we used ab initio, semi-empirical and semi-classical approaches to study 0) ionic crystalline peroxides (e.g. Si and Ba02 [70,71]), (ii) point defects in the bulk and on the sui % of ionic and semi-ionic materials (e.g. corundum, silica and aluminium silicates [72,73]), and (iii) bipolaron formation in lanthanum cuprate (a superconducting material [74]). 

In these and the other cuprate superconductors, the part of the structure that leads to superconductivity is the slab of Cu02 sheets. When more than one sheet is present, they are separated by cation layers, Q (usually Ca or Y) to give a sequence Cu02-(Q-Cu02) i, which forms the superconducting layer in the material. The index n is the total number of Cu02 layers in the phase, which is equal to the formula number of Cu atoms present (Fig. 8.5). 

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