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TT: Tiefe Temperaturen
TT 9: Neue und unkonventionelle Supraleiter
TT 9.2: Talk
Tuesday, March 25, 2003, 09:45–10:00, HSZ301
Competition between Charge Ordering and Superconductivity in Layered Organic Conductors — •Martin Dressel1, Natalia Drichko1,2, and Jaime Merino3 — 11. Physikalisches Institut, Universität Stuttgart, Germany — 2Ioffe Physico-Technical Institute, St. Petersburg, Russia — 3MPI Festkörperforschung, Stuttgart, Germany
Organic charge-transfer salts of the BEDT-TTF family are benchmark systems to probe correlation effects in two-dimensions by exchanging the anions. In the optical spectra of the non-superconducting salt α-(BEDT-TTF)2KHg(SCN)4 a strong feature appears at frequencies of about 200 cm−1 and temperatures below 200 K which indicates the opening of a pseudogap. This is in contrast to the superconducting α-(BEDT-TTF)2NH4Hg(SCN)4 which exhibits metallic-like optical properties down to 2 K. Based on exact diagonalisation calculations of the optical conductivity on an extended Hubbard model at quarter-filling we argue that the proximity of these salts to a charge ordering transition is responsible for the observed pseudogap. Our proposed scenario suggests that the different ground states, including superconductivity, are a consequence of the proximity of these compounds to a quantum phase charge-ordering transition driven by the intermolecular Coulomb repulsion.
[1] M. Dressel et al., cond-mat/0206074