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第18回 原研・兵県大合同コロキウム

日時： 平成18年10月26日(木) 16：30〜
Date and time: 26th Oct. (Thu.) 16:30〜
場所： 兵庫県立大学理学部・大学院講義室(研究棟７階732号室)
Place: Lecture room 732, Faculty of Science, University of Hyogo
講演タイトル Extended Dynamical Mean-Field Approximation: Application to Hubbard Model
講演者： 楠瀬博明 氏（東北大）
Speaker: Dr. Hiroaki Kusunose (Tohoku University)
Abstract:

Dynamics of strongly correlated electron systems has been investigated extensively in context of low-temperature physics in the heavy fermion compounds, the transition metals and some organic materials.A specific feature of such systems is a dual nature of electronic states in one-particle density of states, in which, the high-energy incoherent states (so-called the Hubbard bands) have a spatially localized character, while the low-energy states exhibit an itinerant character with strong temperature dependence. The interplay between the electronic states in two opposite extremes is a vital clue to understand magnetism and superconductivity realized in heavy-fermion systems. It is this aspect however that has hampered many theoretical attempts based on the one extreme, such as weak-coupling approaches or the dynamical mean-field approximation.

I propose a hybrid approach, which takes account of the correction of the spatial fluctuations to the local self-energy obtained by the dynamical mean-field approximation [1]. Using the formalism, it is demonstrated that the one-particle spectral intensity in the two-dimensional Hubbard model at half-filling exhibits the pseudo-gap behavior in the central coherent quasiparticle peak due to the critical antiferromagnetic fluctuation.The specific heat is considerably enhanced by the short-range order, which assists a tendency of the Mott localization showing the reduction of the double occupancy. I will discuss possible future applications with the present formalism, including an anisotropic superconductivity.

[1] H. Kusunose: J. Phys. Soc. Jpn. 75 (2006) 054713.