Berlin 2008 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 32: Correlated Electrons: Poster Session

TT 32.63: Poster

Donnerstag, 28. Februar 2008, 14:00–18:00, Poster B

1/f^α–noise studies of quasi–2D organic charge–transfer salts — •Jens Brandenburg¹, Jens Müller¹, and John Schlueter² — ¹Max–Planck–Institut for Chemical Physics of Solids, Dresden, Germany — ²Argonne National Laboratory, Argonne, USA

Organic charge–transfer salts (κ–(ET)₂X; X=Cu[N(CN)₂]Cl, Cu[N(CN)₂]Br) exhibit various ground states whereas strong (el–el)- and (el–ph)-interactions as well as the quasi–2D Fermi–surface play an important role. Especially the anomalous normal state and the possibly unconventional superconducting phase evolving from an antiferromagnetic Mott–insulating state are in the focus of current investigations. For instance there is an ongoing controversy about the origin of the unusual normal state — characterised by the so called T^*–anomaly — in which a pseudogap behaviour, a crossover from a “bad metal” to a Fermi–liquid and a phase transition of density–wave type is discussed [1]. To understand the exceptional properties of the normal state in more detail, 1/f^α–noise was studied systematically since the intrinsic carrier dynamics is of particular interest. At different temperatures spectra have been measured and analysed with respect to changes of the frequency exponent α and the temperature progression of the normalised spectral weight S_R/R². The behaviour of these quantities is evaluated using a simple mathematical model which allows the extraction of excitation energies causing the excess noise in these materials. The implications of disorder on the ground state properties are discussed.

[1] N. Toyota, M. Lang, J. Müller; Low Dimensional Molecular Metals; Springer (Berlin Heidelberg), 2007