Magnetism and Superconductivity in Highly Correlated Systems

这个项目的目的是探索强关联体系的电子态和由此产生的性质，其中包括高T_c铜酸盐。一般的氧化物、重电子、有机导体和量子线。1.基于t-J模型(Fukuyama，Nagaosa)成功地研究了高T_c铜的磁激发和输运性质。根据PrBa2Cu3O7(大米)的神秘绝缘态的起源，提出了一种新的理论。对二维Hubbard模型进行了详细的数值计算，结果表明随着Mott跃迁的临近，有效质量发散(IMADA)。由于在铜氧化物中没有发现这一点，这一发现使人们对Hubbard模型对高T_c氧化物的有效性产生了怀疑，因此提出了两种不同类型的Mott相变(IMADA)。3.重电子用解析和数值方法(UEDA)探索了一维致密Kondo系统的相图。发现了各向异性超导态下的De Haas van Alphen振荡的可能性。4.精确解的发现(Kuramoto)，并探索了扩展范围t-J模型的严格解(Kuramoto，Kawakami)。5.有机导体基于强关联的Peierls跃迁解释了(DCNQI)2Cu的反常性质(Fukuyama)。6.量子线在半导体量子线中，电子形成一维能带，从而形成Tomonaga-Luttinger液体。研究了它的隧穿特性和输运特性。(福山长高沙)。

The aims of this project are to explore the electronic states and resulting properties of strongly correlated systems, which include high Tc cuprates. oxides in general, heavy electrons, organic conductors and quantum wires.1.High Tc CupratesThe magnetic excitations and transport properties are successfully investigated based on the t-J model (Fukuyama, Nagaosa). A new proposal has been based on the origin of the mysterious insulating state of PrBa_2Cu_3O_7(Rice).2.Oxides. Mott transitionDetailed numerical calculations have been carried on the two-dimensional Hubbard model, which elucidate that the effective mass diverges as the Mott transition is approached (Imada). Since this is not seen in cuprates, this finding casts doubt on the validity of the Hubbard model to high Tc oxides and hence two different types of Mott transition have been proposed (Imada).3.Heavy ElectronsThe phase diagram of one-dimensional dense Kondo system has been explored by both analytical and numerical method (Ueda). The possibility of the de Haas van Alphen oscillation in the anisotropic superconducting state has been pointed out (Miyake).4.Discovery of Exact SolutionsExact solutions of the extended range t-J model have been found (Kuramoto) and explored (Kuramoto, Kawakami).5.Organic ConductorsUnusual properties of (DCNQI)2Cu have been explained based on the Peierls transition with strong correlations (Fukuyama).6.Quantum WiresIn quantum wires made of semiconductors, electrons form one-dimensional band and hence the Tomonaga-Luttinger liquid. The tunneling characteristics and transport properties have been investigated. (Nagaosa, Fukuyama).