Theoretical study of anomalous fluctuation and it's effects on dynamical properties of one-dimensional conductors

我们与实验组合作，通过光发射研究直接观察了碳纳米管的态密度。结果表明，碳纳米管在10k至室温范围内均可实现Tomonaga-Luttinger液态。已知纳米石墨带在费米能附近具有不同于一般金属的反常色散关系。我们研究了这些材料的电子相关性。结果表明，相互作用导致Mott绝缘基态，且对于奇（偶）数之字形链，自旋激发变为无间隙（gap）。奈特位移的分裂和核磁共振弛豫速率的分裂被认为是分子导体中电荷有序的实验证据。然而，在四分之一灌装的情况下，没有人从理论上证明电荷排序会导致这种现象。本研究计算了一维扩展Hubbard模型纯电荷有序态下的Knight位移和NM…More R弛豫速率。这里，RPA考虑了平均场解周围的波动。如图所示，这两个数量在费用排序下显示分裂，正如已经坚持的那样。此外，核磁共振实验估计的电荷歧化量比实际值大。最近，合成了分解比接近2:1的（MDT-TSF）_2X_n、（MDT-ST）_2X_n和（MDT-TS）_2X_n，其中X为一价阴离子，n=0.42 ~ 0.45，并测定了这些化合物的输运性和磁性。材料（MDT-TSF）_2X_n和（MDT-ST）_2X_n表现出金属导电性，并在4 K环境压力下发生超导转变。另一方面，（MDT-TS）_2(AuI_2)_<0.441>在85 K时呈现金属-绝缘子转变。为了阐明为什么金属-绝缘体跃迁发生在不相称带填充的情况下，我们研究了一维扩展Hubbard模型的基态。当考虑阴离子电位时，基态为莫特绝缘子，带宽的增加导致金属-绝缘子转变。这些结果将定性地解释上述实验观察。少

In collaboration with the experimental group, we directly observed the density of state of carbon nanotubes by the photo emission study. It was shown that Tomonaga-Luttinger liquid state is realized in the carbon nanotubes in the wide range of the temperature from 10 K to room temperature. The nano-graphite ribbons are known to have the anomalous dispersion relation near the Fermi energy different from the usual metals. We investigated the electronic correlation of the materials. It was shown that the mutual interaction leads to Mott insulating ground state and the spin excitation becomes gapless (gapped) for the odd (even) number of zigzag chains.2.Splitting of the Knight shift and of the NMR relaxation rate have been considered to be the experimental evidence of charge ordering in the molecular conductors. In the case of quarter-filling, however, no one show theoretically that the charge ordering leads to such phenomena. In the present study, we calculated the Knight shift and the NM … More R relaxation rate in the pure charge ordered state of one-dimensional extended Hubbard model. Here, the fluctuation around the mean-field solution is taken into account by RPA. It is shown that the both quantities show splitting under the charge ordering, as has been already insisted. In addition, the amount of charge disproportionation estimated from the NMR experiments becomes larger than the actual value.3.Quite recently, the materials with incommensurate decomposition ratios close to 2:1 such as (MDT-TSF)_2X_n, (MDT-ST)_2X_n, and (MDT-TS)_2X_n with X being a monovalent anion and n=0.42〜0.45 have been synthesized and the transport and magnetic properties of these compounds have been measured. The materials (MDT-TSF)_2X_n and (MDT-ST)_2X_n show metallic conduction and undergo the superconducting transition at 4 K for ambient pressure. On the other hand, (MDT-TS)_2(AuI_2)_<0.441> shows the metal-insulator transition at 85 K. In order to clarify why the metal-insulator transition occurs in the case of incommensurate band filling, we investigated the ground state of one-dimensional extended Hubbard model with incommensurate lattices. When the potential from the anions is taken into account, the ground state is Mott insulator, and the increase of band width leads to metal-insulator transition. These results will qualitatively explain the experimental observation shown above. Less