Theory of Superconductivity of Strongly Correlated Electrons

高T <@D2c@>D2铜氧化物的重要课题之一是建立正确的Mott转变附近的超导理论，特别是赝能隙区的超导理论。首先，我们基于强耦合方法对d-p模型进行了正常Meissner转变温度的计算，发现真实转变温度T<@D2c@>D2从平均场转变温度有一个定量合理的降低，这是由于随着空穴掺杂的减少，超导涨落增强引起的。然而，由于模型中没有直接考虑电子间的相互排斥，我们不能得到预期的行为T<@D2c@>D2（]SY。（）0接近半填充。为了成功地得到这一结果，我们需要发展一个详细的超导理论的基础上的反铁磁涨落（AFF）基本上在消失的空穴掺杂的限制。在本研究中，我们开发了这样一种AFF理论，用于解释输运量R<@D2xx@>D2、R<@D2xy@>D2和R<@D2zz@>D2的奇怪行为，在高温<@D2c@>D2铜酸盐的正常相中，发现在这些量的数据中所看到的明显矛盾的行为可以在现有的单一理论中得到解释。c超导体的问题是超导涨落在外加磁场中引起的涡旋态问题。在本课题尚未解决的问题中，我们研究了平行于层状材料（如高温铜酸盐）各层的场中涡旋态的相图和关联无序引起的涡旋玻璃态转变，并从已有的实验数据中得到了预期的理论结果。

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.