Berlin 2012 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 2: Focussed session: Frontiers of electronic structure theory: Strong correlations from first principles I (jointly with TT)

O 2.1: Topical Talk

Montag, 26. März 2012, 10:30–11:00, HE 101

Non Uniform Polarizability and Coulomb interactions in Compounds and Interfaces — •George Sawatzky — Physics department University of British Columbia 6224 agricultural road Vancouver BC Canada

The polarizability of relatively ionic compounds like the transition metal or rare earths exhibit quite non uniform polarizabilities requiring a full treatment of the non local field effects when studying the the details of especially relatively short range electron -electron interactions. We discuss how this affects the effective on site Coulomb interactions and show that the intermediate range interactions are not monotonically decreasing with distance even for insulating materials. this has important consequences for the use of models like the Hubbard model especially in low dimensional systems. We will use examples of low dimensional systems as well as the Cuprates, Manganites, Fe Pnictides with strongly polarizable anions in this discussion. We suggest that for the Fe Pnictides the Fe-Fe nearest neighbor coulomb interactions can be much smaller than the next nearest neighbor ones and may turn out to be slightly attractive. Similar non local effects are present at surface and interfaces which can lead to band gap closing rather than conventional band bending for semiconductor metal interfaces. In view of this it is rather important to revisit simple on site only based models and to develop first principles approaches taking into account the non uniform polarizability of the systems studied.