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High Temperature Superconductor

#G-380


High Temperature Ceramic Superconductors: the Ordered State Symmetry, Suppression of Superconductivity

Tech Area / Field

  • MAT-CER/Ceramics/Materials
  • PHY-SSP/Solid State Physics/Physics

Статус
3 Approved without Funding

Дата регистрации
26.07.1999

Ведущий институт
Tbilisi State University / Institute of Physics (Ge), Georgia, Tbilisi

Поддержка институтов

  • Tbilisi State University, Georgia, Tbilisi\nInstitute of Cybernetics, Georgia, Tbilisi

Соавторы

  • University of Patras / School of Engineering, Greece, Patras\nUniversity of California / Hierarchical Scaled Physics and Technologies, USA, CA, Chatsworth\nUniversity of Southern California, USA, CA, Los-Angeles\nCornell University / Laboratory of Atomic and Solid State Physics, USA, NY, Ithaca

Краткое описание проекта

Suggested project devoted to investigation of physical properties and production technology of a new class of superconducting materials-ceramics with unique properties of high temperature superconductivity. These materials have a new perspectives for their application in such areas as engineering, science, transport, medicine, etc.

To make this perspective real the problem of creation of stable materials with high superconducting transition temperature (till room temperature) will se solved. However, it is impossible without clear understanding of fundamental physical processes governing the superconductivity.

The main goals of the project are:

· establishment of particularities of normal and superconductive state of multicomponent ceramic high-temperature superconductors on the basis of lanthanum, yttrium and bismuth-determination of the ordered state symmetry, determination of the fundamental reason of suppression of superconductivity in these materials;

· development of improved technological methods of production of HTSC and composite materials based on multicomponent ceramic systems and synthesis of HTSC ceramics based on the yttrium an bismuth systems of the type YBa2Сu3-yMyO7- ( M=Zn, Ni, or Fe) and Bi2Sr2Ca2Cu3O10 ( BSCCO-2223) with various impurities and composite materials of the type (YBa2Сu3O7-)1-x(Y2BaСuO5)x;

· determination of perspective ways in creation of HTSC materials with improved physical parameters and with controllable properties on the basis of experimental data obtained in consequence of complex investigation their thermal, electrical and magnetic characteristics and also on the basis of their technological development;

· creation of a laboratory breadboard of a superconducting device;

· updating of the working differential pulse calorimeter in order to create a prototype of a commercial device.

Today it can be firmly stated that the nature of a normal and a superconducting state of these materials has not been established so far. There are models of the antiferromagnetic theory of hole mechanisms, the “limiting” Fermi-liquid theory, the dx2-y2 theory, etc. But they cannot provide fully explains results.

For example, the problem of HTSC superconducting state symmetry is one of the fundamental problems of superconductivity physics. The materials under consideration have a laminated structure, where S-wave coupling required by the Bardin – Coper- Shrifer theory, does not show up. Recently it has become evident that d-wave coupling is very important. It is not excluded that there might exist simultaneously several coupling mechanisms. This problem needs to be investigated and clarified. To solve this problem the electron part of heat capacity should be known. The question of separation of the electron part of heat capacity to a high accuracy (in the wide temperature range) is still an open question, since for its solution a specific high-sensitive experimental equipment is required.

In HTSC with magnetic and non-magnetic impurities replacing copper the periodicity in CuO2 is always disturbed resulting in the appearance of local magnetic moments randomly distributed in these planes. In our opinion at rather high impurity concentration spin interactions may cause collective lo-energy perturbations even in the absence of a real long-range magnetic order. These perturbations ma cause suppression of superconductivity. The question of possibility of existence of such collectivemagnetic perturbations in the CuO planes has not been yet considered. It should be solved all the more that, results of the latest works put us on to an idea that there is a certain correlation between impurities magnetic moment and impurities critical temperature which disorders superconductive state. Detection of these perturbations in normal (metallic) and superconducting states is ratherdifficult experimental problem. One of the probable way for its solution is precision measurement of HTSC’s low-temperature heat capacity.


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