Dresden 2011 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 39: Focussed session: Theory and computation of electronic structure: new frontiers III (jointly with HL, DS)

O 39.7: Vortrag

Mittwoch, 16. März 2011, 12:45–13:00, TRE Phy

Construction of low energy Hamiltonians using maximally localized Wannier functions — •Roman Kovacik and Claude Ederer — School of Physics, Trinity College Dublin, Ireland

The theoretical description of correlated electron systems, such as e.g. transition metal oxides, is often based on effective tight-binding (TB) models. A systematic way to obtain realistic TB model parameters from first principles calculations is the construction of maximally localized Wannier functions (MLWFs) [1]. The corresponding TB representation is given by the real space Hamiltonian matrix elements in the MLWF basis. We address two important issues: i) how many orbitals to include in the basis set for the TB model representation, and ii) what is the most appropriate reference point to connect the model and Kohn-Sham band structures (i.e. should the Kohn-Sham band structure be considered as "non-interacting" or as mean-field approximation to the interacting case). We use LaMnO₃, a prototype material for correlation-driven phenomena, as an example for the construction of model Hamiltonians. In particular, we compare a TB description based only on effective Mn e_g bands with a description that explicitly includes also the O p bands, and we analyze the effects of the Hubbard U and the Jahn-Teller distortion on the corresponding TB parameterizations. In addition, we discuss the suitability of different types of Wannier functions for the calculation of TB parameters.

[1] I. Souza, N. Marzari, and D. Vanderbilt, PRB 65, 035109 (2001).