CRITICAL TEMPERATURE OF HIGH-Tc SUPERCONDUCTORS AND BOUNDARY CONDITIONS IN GINZBURG-LANDAU THEORY

New boundary condition for the order parameter in the Ginzburg-Landau theory is applied to the case of CuO2 planes which are the main structural elements responsible for superconductivity in high-T-c superconductors. It was found that the order parameter in these superconductors is significantly depressed in the CuO2 planes. As a result, this boundary condition to the GL equations is found to limit the critical temperature of high-T-c superconductors. Thus, in order to increase T-c of cuprate superconductors, the number of CuO2 planes that are within a short distance of each other in unit cell or insulating properties of the layers located in the vicinity to the CuO2 planes should be increased.