Berlin 2015 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 100: Correlated Electrons: Other Materials
TT 100.4: Talk
Thursday, March 19, 2015, 15:45–16:00, H 3005
Long-range Coulomb interaction in surface systems: From cRPA to GW+DMFT — •Philipp Hansmann1,2, Thomas Ayral1,3, Antonio Tejeda4, and Silke Biermann1 — 1Centre de Physique Theorique, Ecole Polytechnique, CNRS-UMR7644, 91128 Palaiseau, France — 2Max-Planck-Institut für Festkörperforschung, Heisenbergstrasse 1, D-70569 Stuttgart, Germany — 3Institut de Physique Theorique (IPhT), CEA, CNRS, URA 2306, 91191 Gif-sur-Yvette, France — 4Synchrotron SOLEIL, L'Orme des Merisiers, Saint-Aubin, 91192 Gif sur Yvette, France
In spectroscopic (ARPES, cPES) and STM experiments group IV adatoms on semiconductors X:Si/Ge(111) (X=Sn, Si, C, Pb) show competing ground states but are partially in strong contradiction with one another. Ab initio derivation of a low energy Hamiltonian, including constrained RPA calculation for the effective interaction, suggests i) that correlation effects are beyond a single particle treatment and ii) an effective interaction which is not of a local "Hubbard U" type, but has a long-range character. Tackling the problem with standard dynamical mean-field methods (DMFT) is, hence, rather questionable. Instead we depart from the local approximation of DMFT to include, fully self-consistently, non-local effects in a GW+DMFT scheme. We observe that the non-local interaction is responsible for (experimentally observed) charge fluctuations which in some materials (Pb:Si/Ge(111), Sn:Ge(111)) are frozen in a commensurate charge order while in others (Sn:Si(111)) they remain dynamic and explain above mentioned experimental controversies.