Construction of low-energy effective Hamiltonians using Wannier functions formalism

18 May 2005 (Wed), 4:00 pm - 5:30 pm

6F seminar room, Sengen site

Dr. Igor Solovyev

First-Principles Simulation group (II), NIMS-CMSC (NIMS-CMSC 第一原理反応G)

Construction of low-energy effective Hamiltonians using Wannier functions formalism

There is a large class of compounds whose electronic properties are predetermined by the behavior of a limited number of bands located near the Fermi level and well isolated from the rest of the states, and those electronic structure cannot be described properly using conventional methods based on the local-density approximation (LDA). Several typical examples are the perovskites (SrVO$_3$, LaTiO$_3$, etc.), V$_2$O$_3$, Y$_2$Mo$_2$O$_7$, NaCoO$_2$, and many others. The source of the problem is known to be the on-site Coulomb correlations, whose form is greatly oversimplified in LDA. Therefore, many attempts have been done in order to incorporate the physics of on-site Coulomb correlations in LDA. I will discuss the systematic procedure for constructing the effective low-energy Hubbard-type Hamiltonian for these systems using results of first-principle calculations. This procedure consists of three parts: (1) The derivation of the kinetic-energy part using the downfolding method. (2) Construction of Wannier functions. (3) Calculation of screened Coulomb interactions in the basis of Wannier functions. I will also show applications for transition-metal oxides.

Dr. Yoshitaka Tateyama(館山佳尚)