Dresden 2006 – wissenschaftliches Programm
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TT: Tiefe Temperaturen
TT 25: Correlated Electrons - Poster Session
TT 25.2: Poster
Mittwoch, 29. März 2006, 14:30–18:30, P1
Optical response of the low-dimensional organic compound (TMTTF)2AsF6 at the pressure-induced deconfinement transition — •A. Pashkin, C. A. Kuntscher, and M. Dressel — 1. Physikalisches Institut, Universität Stuttgart, 70550 Stuttgart, Germany
The organic (TMTTF)2X salts consist of weakly coupled, half-filled molecular stacks and are prime examples of one-dimensional Mott-Hubbard insulators. In the (TMTSF)2X analogs, where sulfur is substituted by selenium, the coupling along and between the stacks is enhanced, causing a deconfinement transition, i.e., a crossover from a Mott-Hubbard insulator to a higher-dimensional metallic state. Optical spectroscopy was shown to be a key tool to monitor such a deconfinement transition induced by chemical pressure. Similar effects as induced by chemical pressure can also be achieved by applying external pressure.
We studied the pressure dependence (< 6 GPa) of the mid-infrared reflectivity of (TMTTF)2AsF6 for the polarization of the incident radiation along and perpendicular to the molecular stacking axis a. With increasing hydrostatic pressure the infrared response along the stacking axis a approaches that of the highly-conducting TMTSF analogs. The onset of an appreciable Drude-like response for the b′ direction, along which the interstack hopping occurs, is observed above 2.5 GPa suggesting a deconfinement transition. The pressure dependence of the transfer integral tb′ has been extracted. Furthermore, the pressure-dependent optical response along the least conducting axis, c*, is presented.
Supported by the DFG, Emmy Noether-program.