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ERC

CORRELMAT Report Summary

Project ID: 617196
Funded under: FP7-IDEAS-ERC
Country: France

Mid-Term Report Summary - CORRELMAT (Predictive electronic structure calculations for materials with strong electronic correlations: long-range Coulomb interactions and many-body screening)

“Correlated electron materials”, i.e. compounds where strong Coulomb interactions lead to new effects which cannot be accounted for by band-theory count among the most interesting and challenging systems of condensed matter physics. For electrons in partially filled d- or f-shells in transition metal, rare earth or actinide systems, for example, the tendency to delocalization that is inherent to the formation of the solid is counteracted upon by the energetic cost of the Coulomb interaction. In the materials-specific environment of the solid, giving rise to cristal-field and ligand field splittings, the net result is a subtle interplay of charge-, spin-, orbital- and lattice degrees of freedom, and – eventually – a variety of quite unique electronic properties. The CORRELMAT project develops numerical tools for the theoretical description of these phenomena from "first principles", that is, without adjustable parameters. It focuses on the effects of long-range Coulomb interactions and quantum dynamical screening, and includes both the development of the corresponding algorithmic tools and the studies of specific materials systems. Among its most significant advances, three highlights are given below:
1) Our calculations for the transition metal oxide SrVO3 have led to a puzzling prediction of an unoccupied electronic structure much wider than the one calculated in studies using conventional theories, leading to a reinterpretation of experimental spectroscopy results.
2) The development of a comparatively simple and efficient scheme dubbed "Screened Exchange Dynamical Mean Field Theory" has allowed for a detailed comparison of theoretical spectra with angle-resolved photoemission data for different transition metal compounds, demonstrating that the new scheme cures important deficiencies of standard calculational schemes. Moreover, a conceptual understanding of cancellation effects contained in the Kohn-Sham band structure of density functional theory was developed.
3) Role of long-range interactions in 2d systems of adatoms on surfaces:
We worked out a detailed theory (and comparison with different experimental probes) for Sn:Si(111), a prototypical example of a 2d extended Hubbard system (that is, a Hubbard model-like system but with long-range interactions), based on combined many-body perturbation theory and dynamical mean field theory. In particular, we highlighted the role of the time-scale of the experimental probe in the detection of charge-ordering phenomena.

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Record Number: 197668 / Last updated on: 2017-05-16