Regensburg 2007 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 26: Metal-Insulator Transition

TT 26.3: Vortrag

Donnerstag, 29. März 2007, 14:30–14:45, H19

Pressure-induced deconfinement and structural phase transition in the quasi-1D Bechgaard-Fabre salts — •A. Pashkin¹, M. Dressel², and C. A. Kuntscher¹ — ¹Experimentalphysik II, Universität Augsburg, 86159 Augsburg, Germany — ²1. Physikalisches Institut, Universität Stuttgart, 70550 Stuttgart, Germany

We have performed pressure-dependent x-ray diffraction and infrared spectroscopic studies of the organic low-dimensional conductors (TMTTF)₂PF₆ and (TMTSF)₂PF₆, which belong to the family of the Bechgaard-Fabre salts. The (TMTTF)₂PF₆ salt consists of basically uncoupled molecular stacks (half-filled) and is a prime example of a one-dimensional Mott-Hubbard insulator. On the other hand, the coupling between the stacks in the (TMTSF)₂PF₆ salt is high enough to induce metallic conductivity, which is particularly pronounced along the stacking direction. The application of external pressure increases the interstack hopping in the Bechgaard-Fabre salts and allows for a continuous tuning of their electronic properties.

Our pressure-dependent x-ray diffraction data evidence a structural phase transition in (TMTTF)₂PF₆ and (TMTSF)₂PF₆ salts at about 5 and 8 GPa, respectively. Furthermore, we found a pressure-induced deconfinement transition from a one-dimensional Mott-Hubbard insulating state to a higher dimensional metallic state in (TMTTF)₂PF₆ at about 2 GPa. The possible influence of the pressure-induced structural phase transition on the electronic properties is also discussed.

Supported by the DFG, Emmy Noether-program. Provision of beamtime at the ANKA Angströmquelle Karlsruhe is acknowledged.