Colloquium 2004

• 題目:
  Towards a First-Principles Electronic-Structure Approach for Strongly Correlated Materials: Combining the GW Approximation and Dynamical Mean-Field Theory
  
• 講師:
  F. Aryasetiawan氏
  産業技術総合研究所計算科学研究部門
  
• 日時・場所:
  2004年6月29日（火曜日）　13:00から
  物理学専攻 大学院講義室（2-211）にて
  
  
• 要旨：
  　For systems with weak or moderate Coulomb correlations such as sp metals and semiconductors, the GW method is the tool of choice for the determination of excited-state properties from first principles. Application to more strongly correlated systems with partially occupied localized orbitals, however, indicate a need to go beyond the GW approximation (GWA). For example, in ferromagnetic nickel, the GWA is successful in predicting the quasiparticle band narrowing, but neither improves the too large LDA exchange splitting nor reproduces the famous 6eV photoemission satellite.
  　Recently, a new approach to the electronic structure of strongly correlated materials was developed. This approach, called LDA+DMFT, combines the dynamical mean-field theory (DMFT) of correlated electron models with LDA. It is a Green's function technique, but unlike the GWA, it does not treat the Coulomb interaction from first principles. Instead, an effective Hamiltonian involving Hubbard-like parameters is used, as well as a double-counting term.
  　We propose a scheme combining the GWA with DMFT [1] which enables one to treat strong interaction effects. It avoids the conceptual problems inherent in conventional LDA+DMFT method, such as the Hubbard interaction parameters and double-counting terms. We apply a simplified version of the approach to the electronic structure of ferromagnetic nickel and find encouraging results. We discuss some open questions and future challenges.
  
  [1] S. Biermann, F. Aryasetiawan, and A. Georges, Phys. Rev. Lett. 90, 086402 (2003).
  
• 連絡先:　大川房義　(x 2694)

物理コロキウム世話人： 中山隆一 (x 2696) ， 北　孝文 (x 2687)