Asymmetric band widening by screened exchange competing with local correlations in SrVO3: new surprises on an old compound from combined GW and dynamical mean field theory GW+DMFT

摘要

The very first dynamical implementation of the combined GW and dynamical meanfield scheme "GW+DMFT" for a real material was achieved recently [J.M. Tomczaket al., Europhys. Lett. 100 67001 (2012)], and applied to the ternarytransition metal oxide SrVO3. Here, we review and extend that work, giving notonly a detailed account of full GW+DMFT calculations, but also discussing andtesting simplified approximate schemes. We give insights into the nature ofexchange and correlation effects: Dynamical renormalizations in the Fermiliquid regime of SrVO3 are essentially local, and nonlocal correlations mainlyact to screen the Fock exchange term. The latter substantially widens thequasi-particle band structure, while the band narrowing induced by the formeris accompanied by a spectral weight transfer to higher energies. Mostinterestingly, the exchange broadening is much more pronounced in theunoccupied part of spectrum. As a result, the GW+DMFT electronic structure ofSrVO3 resembles the conventional density functional based dynamical mean field(DFT+DMFT) description for occupied states, but is profoundly modified in theempty part. Our work leads to a reinterpretation of inverse photoemissionspectroscopy (IPES) data. Indeed, we assign a prominent peak at about 2.7 eVdominantly to eg states, rather than to an upper Hubbard band of t2g character.Similar surprises can be expected for other transition metal oxides, callingfor more detailed investigations of the conduction band states.