Study of strongly correlated electron systems in infinite dimensions

Abstract

Strongly correlated electron systems such as the heavy electron systems and the high T(sub c) cuprates were studied by using the dynamical mean field theory in order to reduce the problem of an electron system on a lattice to that of an impurity embedded in an effective medium. The impurity problem was solved with the quantum Monte Carlo method, and the result in infinite dimensions was obtained. The nondegenerate symmetric periodic Anderson model was investigated to clarify the origin of the gap in the Kondo insulators, and the one-particle spectral function, the charge and the spin excitation spectral were calculated. By the study on the magnetic susceptibility of the model, it was found that the interband contribution was enhanced by the interaction. The two-band Hubbard model including both of the Mott-Hubbard case and the charge transfer case has been studied. This study clarified the character of the electronic states near the metal-insulator transition point driven by the electron correlation and the shift of the one-particle spectral weight as a function of the electron number or of the strength of the interaction. The dependence of the spectral function on the strength of the interaction was studied.

格子の電子系問題を有効媒質に埋め込まれた不純物の問題に適応するために、動力学的平均場理論を用いて、重い電子系および高Tc銅酸塩のような強相関電子系を研究した。不純物問題は量子モンテカルロ法で解き、無限次元における結果を得た。Kondo絶縁体におけるギャップの起点を明らかにするために非縮退型対称周期的Anderson模型を検討し、1粒子スペクトル関数および電荷とスピン励起スペクトルを計算した。模型の磁化率の研究により、バンド間の寄与が相互作用により高まることが分かった。電子相関により引き起こされる金属-絶縁体転移点の近傍の電子状態の特質、および電子数あるいは相互作用強度の関数としての1粒子スペクトル重量の移動を明らかにするために、Mott-Hubbard事例と電荷移行事例の両方を含む2バンドHubbard模型を研究した。相互作用強度におよぼすスペクトル関数の依存性を検討した。