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TT: Tiefe Temperaturen

TT 16: Posters Correlated Electrons, Measuring Devices, Cryotechnique

TT 16.63: Poster

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

Pressure-induced dimensional crossover in the quasi-one-dimensional Mott-Hubbard insulator (TMTTF)₂AsF₆ — •A. Pashkin, M. Dressel, and C. A. Kuntscher — 1. Physikalisches Institut, Universität Stuttgart, 70550 Stuttgart, Germany

The organic (TMTTF)₂X salts consist of basically uncoupled molecular stacks (half-filled) and are prime examples of one-dimensional Mott-Hubbard insulators. With increasing interchain hopping the systems become more metallic, as can be realized in the metallic TMTSF analogs where the coupling between the chains is enhanced. This dimensional crossover can be best explored experimentally by tuning of the interstack interaction with external pressure. A complete theoretical description is still missing for the case of a strictly one-dimensional half-filled chain when going to a more two-dimensional system.

We have studied the pressure dependence (<10 GPa) of the reflectivity of (TMTTF)₂AsF₆ along the molecular stacking axis a and along the b-direction. The evolution of the reflectivity with increasing pressure demonstrates the gradual onset of a Drude-like conductivity along b’. At high enough pressure (>3 GPa) the infrared response along both directions becomes similar to that of the conducting TMTSF-analogs in accordance with the generalized temperature-pressure phase diagram. We also discuss the behavior of the phonon modes with change of the pressure.