Dresden 2009 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 29: Correlated Electrons: Low-dimensional Systems - Materials 2

TT 29.6: Vortrag

Mittwoch, 25. März 2009, 15:30–15:45, HSZ 301

Fluctuation spectroscopy studies of the quasi–2D organic conductors κ−(BEDT−TTF)₂X — •Jens Brandenburg¹, Jens Müller¹, and John A. Schlueter² — ¹Max Planck Insitute of Chemical Physics of Solids, Dresden, Saxony, Germany — ²Argonne National Laboratory, Argonne, Illinois, USA

The family of quasi–2D organic conductors κ−(BEDT−TTF)₂X with X = Cu[N(CN)₂]Cl, Cu[N(CN)₂]Br and Cu(NCS)₂ are model systems for low–dimensional metals exhibiting both strong electron–electron and electron–phonon interactions. The interplay of charge, spin, and lattice degrees of freedom lead to a variety of different magnetic–insulating, metallic, and superconducting ground states [1]. Fluctuation spectroscopy has been used to study the intrinsic charge carrier dynamics in this class of materials for the first time. Here, noise measurements as a function of temperature and magnetic field are presented for three compounds located at different positions of the phase diagram. A comparison with the resistance of the samples reveals additional features one of which can be assigned to the activation energy of the glass–like ordering of the ethylene endgroups of the ET–molecules [2]. For the materials close to the bandwidth controlled Mott transition we discuss a steep increase of the noise power upon decreasing temperature in the framework of percolation theory as due to the coexistence of antiferromagnetic insulating and superconducting phases [2].

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

[2] J. Müller, J. Brandenburg, J. A. Schlueter; to be published