Dresden 2017 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 5: Correlated Electrons: (General) Theory 1

TT 5.11: Talk

Monday, March 20, 2017, 12:15–12:30, HSZ 304

Non-local screening effects in strongly correlated materials — •Evgeny Stepanov — Radboud University, Institute for Molecules and Materials, 6525AJ Nijmegen, The Netherlands

Dynamical mean-field theory (DMFT) is one of the most popular approaches to strongly correlated systems. It provides an approximate solution of the Hubbard model by mapping it to a local impurity problem. Later, an extended dynamical mean-field theory (EDMFT) was introduced to include collective degrees of freedom into DMFT. Unfortunately, these collective excitations have a strongly non-local nature, so EDMFT is insufficient and it was necessary to develop some extensions to treat non-local correlations. To go beyond EDMFT, one needs to determine the corrections to the electronic self-energy and polarization operator that describe excitations that were not taken into account at the impurity level. Therefore, the great care should be taken to avoid double counting of correlation effects when merging EDMFT with the extension part.

Here we introduce the Dual Boson (DB) approach and show, that existing up to now approaches, such as EDMFT+GW, can be easily derived from the exact dual transformations and should be corrected in order to obtain better physical description of strongly correlated systems. The DB theory is free from double counting problems by construction, therefore, for the same computational complexity as the standard EDMFT+GW approach, the Dual Boson formalism significantly improves physical results and solves the double-counting problem.