QSGW+DMFT: an electronic structure scheme for the iron pnictides and beyond

Jan M Tomczak

doi:10.1088/1742-6596/592/1/012055

Abstract

While in strongly correlated materials one often focuses on local electronic correlations, the influence of non-local exchange and correlation effects beyond band-theory can be pertinent in systems with more extended orbitals. Thus in many compounds an adequate theoretical description requires the joint treatment of local and non-local self-energies. Here, I will argue that this is the case for the iron pnictide and chalcogenide superconductors. As an approach to tackle their electronic structure, I will detail the implementation of the recently proposed scheme that combines the quasi-particle self-consistent GW approach with dynamical mean-field theory: QSGW+DMFT. I will showcase the possibilities of QSGW+DMFT with an application on BaFe2As2. Further, I will discuss the empirical finding that in pnictides dynamical and non-local correlation effects separate within the quasi-particle band-width.

Highlights

Many phenomena in correlated materials –the Kondo effect, the Mott insulator, etc.– can be described by local correlations
I have recently shown[26] that using quasi-particle self-consistent (QS) GW [27, 28], a many-body perturbation theory[29] that excels at treating non-local exchange and includes some non-local correlation effects, these problems are solved: (1) For LiFeAs QSGW yields a Fermi surface in excellent in agreement with experiment, (2) a non-local selfenergy shift shrinks both electron and hole pockets in BaFe2As2 to about half their size with respect to density functional theory (DFT), as shown in figure 1
We proposed to merge QSGW with dynamical mean field theory (DMFT) in a “QSGW+DMFT” approach[26] that retains most of the advantages of GW+DMFT[30] at a significantly reduced computational complexity

Summary

Introduction

Many phenomena in correlated materials –the Kondo effect, the Mott insulator, etc.– can be described by local correlations. I will discuss the empirical finding that in pnictides dynamical and non-local correlation effects separate within the quasi-particle band-width. I have recently shown[26] that using quasi-particle self-consistent (QS) GW [27, 28], a many-body perturbation theory[29] that excels at treating non-local exchange and includes some non-local correlation effects, these problems are solved: (1) For LiFeAs QSGW yields a Fermi surface in excellent in agreement with experiment, (2) a non-local selfenergy shift shrinks both electron and hole pockets in BaFe2As2 to about half their size with respect to DFT, as shown in figure 1.

Results

Conclusion