Dresden 2009 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 6: Postersession Correlated Electrons: (General) Theory, Low-Dimensional Systems, Kondo Physics, Heavy Fermions, Quantum-Critical Phenomena
TT 6.29: Poster
Monday, March 23, 2009, 13:00–16:45, P1A
Magnetic-field dependence of the T*-anomaly in quasi-2D organic superconductors — Jens Brandenburg1, •Pintu Das1, Jens Müller1,2, Michael Lang2, Franziska Weickert1,3, Marek Bartkowiak3 und Jochen Wosnitza3 — 1Max–Planck–Institut für Chemische Physik fester Stoffe, Dresden — 2Johann–Wolfgang–von–Goethe Universität, SFB/TR49, Frankfurt am Main — 3Hochfeld–Magnetlabor Dresden, Forschunszentrum Dresden–Rossendorf, Dresden
The family of quasi-2D superconductors κ−(BEDT−TTF)2X are model systems for strongly correlated low–dimensional metals. Recently, the unusual normal–conducting state — characterized by a line of anomalies T* (in the order of 40 K) — has attracted considerable attention: a pseudo-gap" behavior in analogy to the high-Tc cuprates, a crossover from an incoherent "bad" metal to a coherent Fermi–liquid regime, and a density–wave–type phase transition have been suggested as possible scenarios. To investigate the possibility of a magnetic origin we carried out detailed transport measurements in pulsed magnetic fields up to 60 T. For two different compounds, X = Cu[N(CN)2]Br and Cu(NCS)2, we observed a maximum in the relative magnetoresistance change right around T*. This indicates the significance of magnetic degrees of freedom which are coupled to the transport properties. Also, for the first time we were able to determine the magnetic–field dependence of T* showing a small negative shift with increasing field. We discuss the implications of our experimental data for possible models explaining the anomalous normal–conducting state.