Berlin 2005 – wissenschaftliches Programm

Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe

TT: Tiefe Temperaturen

TT 16: Posters Correlated Electrons, Measuring Devices, Cryotechnique

TT 16.28: Poster

Samstag, 5. März 2005, 11:00–16:30, Poster TU C

Optical studies of the bandwidth controlled Mott-Hubbard transition in 2-dim organic charge transfer salts. — •Daniel Faltermeier, Michael Dumm, and Martin Dressel — 1. Physikalisches Institut, Universität Stuttgart, Pfaffenwaldring 57, 70550 Stuttgart

The quasi two-dimensional organic charge-transfer salts κ-(BEDT-TTF)₂Cu[N(CN)₂]Br_xCl_1−x have attracted lots of interest because of their unique physical properties: by applying moderate external pressure or by alloying with Br or Cl the ground state can be switched between an antiferromagnetic insulating and superconducting state. In contrast to the high-T_c cuprates the Mott-Hubbard-transition is achieved by bandwidth control and not by hole doping. We present polarization dependent reflection data of the κ-(BEDT-TTF)₂ salts in a spectral range from 50 to 8000 cm^-1 with different concentration x of Br and in a temperature range from 5 to 300 K. Starting from the pure Cl component, with increasing Br concentration and decreasing the temperature, the material becomes continuously more and more metallic, what is characterized by a strong Drude tail at low frequencies. Furthermore, we present detailed analysis of the optical conductivity in the vicinity of the insulator-to-metal transition including e.g. the broad absorption hump in the mid-infrared region.