#
2007 APS March Meeting

## Volume 52, Number 1

##
Monday–Friday, March 5–9, 2007;
Denver, Colorado

### Session U13: Focus Session: Maganites, Titanates, & Vanadates

8:00 AM–11:00 AM,
Thursday, March 8, 2007

Colorado Convention Center
Room: Korbel 4C

Sponsoring
Units:
DMP GMAG

Chair: Yoichi Horibe, Rutgers University

Abstract ID: BAPS.2007.MAR.U13.1

### Abstract: U13.00001 : Combining DFT and Many-body Methods to Understand Correlated Materials*

8:00 AM–8:36 AM

Preview Abstract
Abstract

####
Author:

Igor Solovyev

(National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047, Japan)

Electronic and magnetic properties of strongly-correlated
systems are typically controlled by a limited number of
electronic states, located near the Fermi level and well isolated
from the rest of the spectrum. This opens a formal way for
combining
the first-principles methods of electronic structure
calculations,
based on the density-functional theory (DFT), with model many-
body
methods, formulated in a restricted Hilbert space of states near
the Fermi level. The core of this project is the construction of
``\textit{ab initio} model Hamiltonians'', which would
incorporate
the physics of on-site Coulomb correlations and provide a
transparent
physical picture for the low-energy properties of strongly-
correlated
systems. First, I will describe a systematic procedure for
constructing
such an effective Hubbard-type model, which consists of three
major
steps, starting from the electronic structure in the local-
density
approximation.$^1$ (i) Construction of the kinetic-energy part
using an exact version of the downfolding method;$^{1,2}$ (ii)
Construction of the Wannier functions; (iii) Calculation of
screened
Coulomb interactions using a hybrid approach, which combines the
random
phase approximation with the constraint DFT.$^{1,3}$ Then, I will
illustrate abilities of this method for resolving a number of
controversial
issues, related with the interplay of the experimental lattice
distortion
and magnetic properties of four narrow $t_{2g}$ band perovskite
oxides
(YTiO$_3$, LaTiO$_3$, YVO$_3$, and LaVO$_3$), for which the
obtained
Hamiltonian was solved using a number of techniques, including
the
Hartree-Fock (HF) approximation,$^4$ the second-order
perturbation
theory and the $t$-matrix approach for the correlation energy,$^
{4,5}$
and a variational superexchange theory, which takes into account
the
multiplet structure of the atomic states.$^4$ I will argue that
the crystal distortion imposes a severe constraint on the form
of the
possible orbital states, which favors the formation of
experimental
magnetic structures in YTiO$_3$, YVO$_3$, and LaVO$_3$, even at
the level
of HF approximation. The correlation effects systematically
improve the
agreement with the experimental data and additionally stabilize
the
experimentally observed G- and C-type antiferromagnetic states in
YVO$_3$ and LaVO$_3$. The role of relativistic spin-orbit
interaction
will be also discussed.
\newline
$^1$ I.~V.~Solovyev, Phys.~Rev.~B~\textbf{73}, 155117 (2006).
\newline
$^2$ I.~V.~Solovyev, Z.~V.~Pchelkina, and V.~I.~Anisimov, cond-
mat/0608528.
\newline
$^3$ I.~V.~Solovyev and M.~Imada, Phys.~Rev.~B~\textbf{71}, 045103
(2005).
\newline
$^4$ I.~V.~Solovyev, Phys.~Rev.~B~\textbf{74}, 054412 (2006).
\newline
$^5$ I.~V.~Solovyev, cond-mat/0608625.

*I which to express my thanks to Masatoshi Imada for valuable interactions on the early stages of this project.

To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2007.MAR.U13.1