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TT: Tiefe Temperaturen

TT 11: Postersitzung II (Metall-Isolator-Überg
änge, Phasenüberg
änge in Quantensystemen, Theorie: Systeme korrelierter Elektronen)

TT 11.12: Poster

Dienstag, 25. März 2003, 14:30–19:00, P2c, P2d

Infrared spectroscopy of the Mott-Hubbard insulator to superconductor transition in κ-(ET)₂Cu[N(CN)₂]Br_xCl_1−x — •Jakob Barz, Michael Dumm, and Martin Dressel — 1.Physikalisches Institut, Universität Stuttgart, 70550 Stuttgart

At low temperatures, the quasi two-dimensional charge-transfer salt κ-(ET)₂Cu[N(CN)₂]Cl is an antiferromagnetic Mott-Hubbard insulator. In contrast, the isostructural compound κ-(ET)₂Cu[N(CN)₂]Br is an organic superconductor with T_c = 11.6 K. We investigated the critical region in the vicinity of the insulator to superconductor transition by temperature dependent optical reflectivity measurements on κ-(ET)₂Cu[N(CN)₂]Br_xCl_1−x. The spectra of the single crystals were collected in the frequency range from 20 to 10000 cm⁻¹; the optical conductivity was obtained by Kramers-Kronig transformation. The salts with high Br content show Drude-like behavior down to low temperatures as expected for metals. Contrary, the insulating character of the systems with higher Cl content is emphasized by a significant reduction of low-energy spectral weight.