Low-dimensional electronic states and electron coorelation in organic conductors

本研究的目的是根据导电电子之间的库仑关联来阐明有机导体中低维电子系统的特征性质。研究成果总结为两点：(1)确立了强磁场在低维电子性质研究中的重要作用，阐明了由强磁场引起的各种电子性质及其产生的理论基础。(2)阐明了有机导体中一种新型的金属-绝缘体转变的物理机制，在基于TMTSF分子的一维电子性质研究中，阐明了磁阻随磁场方向与晶轴夹角的变化规律，基本可以用基于能带理论和Boltzman方程的半经典理论来解释。这一结果为二维e…的研究提供了共同的基础。更多电子系统介绍如下。对于一维自旋密度波态中可能存在的内部相结构和电子相关性，我们最初的想法是从强磁场下单粒子输运的角度来研究这一问题，揭示了能带结构的变化导致了自旋密度波态中电子结构的变化。通过测量高压下随角度变化的磁阻振荡，研究了基于BEDT-TTF分子的二维系统的电子性质，以揭示低温下出现所谓反常状态的原因。一维DCNQI导体中的金属-绝缘体相变是由于一维系统的Peierls相变、高关联系统的Mott相变、铜离子周围的Jahn-Teller效应、铜2*态的磁自旋及其熵的相互作用所致。较少

The purpose of the present research is to clarify characteristic properties of low-dimentional electronic systems in organic conductors in the light of the Coulomb correlation between conduction electrons. Research results are summarized in two points : (1) We established the important role of high magnetic fields in studying low-dimensional electronic properties, and clarified a wide variety of electronic properties caused by the magnetic fields and theoretical basis for these phenomena. (2) We made clear the physical mechanism for a novel metal-insulator transition in some organic conductors.In the study on one-dimensional electronic properties based on TMTSF molecule it was clarified that various features of magnetoresistance as a function of the angle between the magnetic field direction and the crystalline axis are explained basically by the semi-classical theory based on the band theory and the Boltzman equation. This results gave a common basis for the study on two-dimensional e … More lectronic systems described below. With respect to the possible internal phase structure in the spin-density wave state caused by the one-dimensionality and the electron correlation our original idea to investigate this from the view point of the single particle transport under high magnetic fields revealed that a band structural change caused the change in the electronic structure in the spin-density wave state.Electronic properties of the two-dimensional systembased on BEDT-TTF molecules were studied by measurements of the angle-dependent magnetoresistance oscillations under high pressures to made clear the origin of the so-called anomalous state appearing at low temperatures. In addition we found the presence of three-dimensionality causes an anomalous increase of magnctoresistance for the magnetic filed close to the conducting plane.The metal-insulator transition in one-dimensional DCNQI conductors was found to be due to interplay among the Peierls transition of one-dimensional system, the Mott transition of highly correlated system, the Jahn-Teller effect around the copper ion, magnetic spins of copper 2*state and their entropy. Less