Cooperation and competition of electron-electron interaction and electron-lattice interaction in oxides

1.“高Tc铜酸盐中的电子相关和电子-晶格相互作用”：研究了铜超导体中电子相关和电子-晶格相互作用的合作与竞争。特别关注ab平面的半呼吸模式。电子相关的影响被考虑为电子-声子相互作用的顶点校正。我们揭示了氧离子的半呼吸模式支持d波超导性，并再现了在非弹性中子散射中观察到的异常声子色散关系。“轨道有序系统中的稀释效应”：研究了远程轨道有序系统中的稀释效应。最近的实验结果表明，与稀释磁体相比，在KCuF_3中掺杂Zn后，轨道有序温度迅速降低。利用蒙特卡罗模拟研究了基于电子-电子相互作用和电子-声子相互作用的理论模型。结果表明，与常规渗流情景的预测结果相比，轨道有序温度的降低是显著的。这是由于轨道之间独特的相互作用。“钒酸钙钛矿中的电子-电子相互作用和电子-晶格相互作用”：钒酸钙钛矿R_<1-x>A_xVO_3表现出自旋- c /轨道- g和自旋- g /轨道- c两种自旋和轨道有序模式。实验表明，少量空穴的掺杂可以使自旋- g /轨道- c相快速坍缩。基于同时考虑电子-电子相互作用和电子-晶格相互作用的模型，我们研究了自旋和轨道有序钒酸盐中的空穴运动。

1."Electron correlation and electron-lattice interaction in high Tc cuprates" : Cooperation and competition between electron correlation and electron-lattice interaction in cuprate superconductors are investigated. In particular, the half-breathing mode in the ab plane is focused on. Effects of the electron correlation are taken into account as a vertex correction of the electron-phonon interaction. We reveal that the half-breathing mode of the oxygen ions supports the d-wave superconductivity, and reproduce the anomalous phonon dispersion relation observed in the inelastic neutron scattering.2."Dilution effects in orbital ordered system" : Dilution effects on the long range orbital ordered systems are examined. Recent experimental results show that the orbital ordering temperature rapidly reduces with doping Zn in KCuF_3, in comparison with the diluted magnets. The theoretical model based on the electron-electron interaction and the electron-phonon interaction is investigated by using the Monte-Carlo simulation. We show that the decreasing of the orbital ordering temperature is remarkable in comparison with the prediction of the conventional percolation scenario. This is attributed to the unique interaction between orbitals.3."Electron-electron interaction and electron-lattice interaction in perovskite vanadates" : The perovskite vanadates R_<1-x>A_xVO_3 show the two kinds of spin and orbital ordered patters, i.e. spin-C/orbital-G and spin-G/orbital-C orders. It is revealed experimentally that by doping of a tiny amount of holes, the spin-G/orbital-C phase is rapidly collapsed. We examine the hole motion in the spin and orbital ordered vanadates based on the model where the electron-electron interaction and the electron-lattice interaction are taken into account simultaneously.