"Determination of the space anisotropy of order parameter phase of the high temperature superconductivity"

Supported by: Russian Foundation for Basic Research, Project number 98-02-17366
Duration: January 1999 - January 2001
Supervisor: Evgueni A. Stepantsov, Ph.D., Shoubnikov Institute of Crystallography RAS, Moscow, Russian Federation
Supervisor in IREE RAS: Gennady A. Ovsyannikov, Doctor of Sciences in Physics and Mathematics

Summary

More than 10 years have passed since the discovery of the high-temperature superconductivity in the metal oxide ceramics, but the nature of the superconducting state in these remains unclear. It was found out that while ordinary, low-temperature, metal, superconductors always show the s-type of the wave function of the superconducting electrons, isotropic on the impulse directions, the metal oxide superconductors wave function has more complex structure. A number of experiments proposes the d-type of the wave function, having two directions with positive and two (in orthogonal direction) - with negative sign of the order parameter. This corresponds to the 180-degree shift of the wave function phase. The effect of the wave function phase is most efficiently revealed in the experiments with Josephson structures, that are used for determination of the dependences on the pulse direction. Some experiments still cannot be explained using simple d-pairing model. This demands new experiments to determine the order parameter symmetry. The information on the order parameter anisotropy itself doesn't provide us with the superconducting pairing mechanism, but can be an important arguement when choosing the certain theoretical model.


Project objectives

The phase sensitivity of the grain boundary Josephson junctions was supposed to be used for measurements of the phase anisotropy of the order parameter in HTSC. The project goals are:

  1. to study in detail the dependences of the electrophysical and magnetic parameters of the HTSC grain boundary junctions at different orientations of the current flow direction relatively to the boundary;

  2. to study in detail the dependences of the microwave parameters of the HTSC grain boundary junctions at different orientations of the current flow direction relatively to the boundary;

  3. to study more complex superconducting structures, where the effects, sensitive to the phase differences of the superconducting wave functions of the junction, can be revealed.


Group activity

In the framework of the project the HTSC group carries out the following tasks: