Theoretical study of anomalous electronic states of vanadium oxides with pyroclore lattice structures

我们对强关联电子系统进行了理论和计算研究，特别是旨在阐明过渡金属氧化物和分子导体的异常电子性质的机制。本文采用密度矩阵重整化群（DMRG）方法对赝一维模型的电子态进行了高精度计算。主要结果如下：1.阐明了三角晶格Hollandite化合物Bi_xV_8O_2的电荷和轨道有序化机制<16>; 2.阐明了辉石化合物NaTiSi_2O_3的轨道有序化和自旋单重态形成机制6.3.我们阐明了在大电荷涨落态中出现的反常自旋激发的性质提出了CuO双链体系中电荷有序态量子熔化时自旋能隙液态形成的新机制。6.计算了一维扩展Hubbard模型基态的精确电子相图。7.提出了CuO双链体系中电荷有序态量子熔化时自旋能隙液态形成的新机制。三重态超导电性，出现在两链的超导键哈伯德模型。

We have made theoretical and computational studies of strongly correlated electron systems, aiming in particular at elucidation of the mechanisms of the anomalous electronic properties of transition-metal oxides and molecular conductors. We have used the density-matrix renormalization group(DMRG) method for calculating the electronic states of pseudo-one-dimensional models in high accuracy. The main results obtained are the following.1.We have clarified the mechanism of the charge and orbital ordering of the triangular-lattice Hollandite compound Bi_xV_8O_<16>.2.We have clarified the mechanism of the orbital ordering and spin-singlet formation in pyroxene compound NaTiSi_2O_6.3.We have clarified the nature of the anomalous spin excitations that appear in the states of large charge fluctuation.4.We have elucidated the anomalous charge dynamics in the CuO double-chain systems.5.We have proposed the novel mechanism of formation of the spin-gap liquid state that appears when the quantum melting of charge-ordered state occurs in the CuO double-chain systems.6.We have calculated the precise electronic phase diagram of the ground state of the one-dimensional extended Hubbard model.7.We have proposed the novel mechanism of the spin-triplet superconductivity that appears in the two-chain zigzag-bond Hubbard model.