|Budget Amount *help
¥3,000,000 (Direct Cost : ¥3,000,000)
Fiscal Year 1998 : ¥1,300,000 (Direct Cost : ¥1,300,000)
Fiscal Year 1997 : ¥1,700,000 (Direct Cost : ¥1,700,000)
One of the most important subjects in high-T<@D2c@>D2 cuprates is to construct a correct theory of superconductivity close to the Mott transition, in particular, of so-called the pseudogap regime. First, we performed calculations of normal-Meissner transition temperature based on the strong-coupling approach for the d-p model and found that the true transition temperature T<@D2c@>D2 shows a quantitatively reasonable reduction, induced by superconducting fluctuation enhanced with decreasing the hole-doping, from the mean filed transition temperature. However, since the mutual repulsion between electrons was not directly included in the model, we could not obtain the expected behavior T<@D2c@>D2 (]SY.tri-substituted left.[) 0 near the half filling. To succeed in getting this result, we will need to develop a detailed superconductivity's theory based on the antiferromagnetic fluctuation (AFF) essential in the limit of vanishing holedoping. In this research, we developed such an AFF theory for the purpose of explaining strange behaviors of transport quantities, R<@D2xx@>D2, R<@D2xy@>D2, and R<@D2zz@>D2, in the normal phase of high-T<@D2c@>D2 cuprates and showed that apparently contradicting behaviors seen among data of these quantities can be explained within the present single theory.
Another important subject in high-T_c superconductors is the problem of vortex states induced by the superconducting fluctuation in an applied magnetic field. Among unsolved issues in this subject, we have studied at this time the phase diagram of vortex states in fields parallel to the layers of a layered material such as high-T_c cuprates and the vortex glass transiton induced by correlated disorder and, for both issues, obtained theoretical results expected from available experimental data.