第3回 物理工学科教室談話会 (講師:Dr. Ansgar Liebsch)

日 時 平成21年11月26日(木)午後2時から
場 所 工6号館 3階 セミナー室A
講演者 Prof. Dr. Ansgar Liebsch (Research Center Juelich)
題 目 Fermi-liquid, non-Fermi-liquid, and Mott phases in iron pnictides and cuprates

The role of Coulomb correlations in the iron pnictide LaFeAsO is studied by generalizing exact diagonalization dynamical mean field theory to five orbitals.[1] For rotationally invariant Hund’s rule coupling a continuous transition from a paramagnetic Fermi-liquid phase to a non-Fermi-liquid metallic phase exhibiting frozen moments is found at moderate Coulomb energies. For Ising-like exchange, this transition is first order and occurs at a lower critical Coulomb energy. The correlation-induced scattering rate as a function of doping relative to half-filling, i.e., delta=n/5-1, where n=6 for the undoped material, is shown to be qualitatively similar to the one in the two-dimensional single-band Hubbard model.[2] In this scenario, the parent Mott insulator of LaFeAsO is the half-filled n=5 limit, while the undoped n=6 material corresponds to the critical doping region delta_c ~ 0.2 in the cuprates, on the verge between the Fermi-liquid phase of the overdoped region and the non-Fermi-liquid pseudogap phase in the underdoped region.
[1] H. Ishida and A. Liebsch, arXiv:0911.1940 submitted to PRB
[2] A. Liebsch and N.H. Tong, Phys. Rev. B 80, 165123 (2009)
紹介教員 今田正俊教授・有田亮太郎准教授