Development of the Band Calculation based on the Dynamical Mean Field Theory

本项目的主要目的是开发通用的基于动力学平均场理论的能带计算方法，并研究强关联电子系统的相关现象。(1)提出了一种求解辅助单点近藤问题的方法NCAf 2 v。这使我们能够包括正确的交换过程，通过f1-f2价态波动沿着f1-f0波动。通常的NCA方法限制了后者。(2)将LMTO方法与NCAf 2 v方法相结合，编制了谱带计算程序。计算中考虑了自能的自旋-轨道（SO）劈裂和晶场劈裂（CF）。(3)将该方法应用于Ce金属和CeSb，在Ce金属的y相中，CF劈裂能大于Kondo温度，而在a相中，Kondo温度大于CF劈裂。光电子发射谱中SO侧峰变得明显，与实验结果相似，在CeSb中再现了PBS的双峰结构。由于4f带的强关联引起的有效杂化在费米能级处出现一个小峰，预计会有相当高的近藤温度。基于紧束缚模型研究了YbB_（12）等Kondo绝缘体材料的光学和热电效应，并研究了PrOs_4Sb_（12）等多极有序体系的动力学激发。

The main purposes of this project were to development the band calculation method based on the dynamical mean field theory for general use, and to study related phenomena of strongly correlated electron systems.(1) A method named as NCAf2v' was developed to solve the auxiliary single site Kondo problem. This enables us to include the correct exchange process through the f1-f2 valence fluctuation along with the f1-f0 fluctuation. The usual NCA method restricts the latter one.(2) The band calculation program was developed by the combination of the LMTO and the NCAf2v' method. The spin-orbit (SO) splitting and the crystalline filed splitting (CF) of the self energy were included in the calculation.(3) The method was applied to Ce metal and CeSb.In the y-phase of Ce metal, the CF splitting energy is larger than the Kondo temperature, while in the a-phase the Kondo temperature is larger than the CF splitting. The SO side peak becomes conspicuous in photo-emission-spectra similarly to the experimental results.In CeSb two peaks structure of PBS was reproduced. A rather higher Kondo temperature is expected because a small peak appears at the Fermi energy in the effective hybridization, which is caused by the strongly correlated 4f band.The magnetic alloy problem of 3d metals was also studied. The Curie temperature id decreased by the correlation type fluctuation effects.The optical and thermoelectric effects of Kondo insulator materials such as YbB12 were studied based on the tight biding model which reproduces the main features of band structures.The dynamical excitation of multipolar ordering systems such as PrOs4Sb12 was also studied.