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TT: Fachverband Tiefe Temperaturen
TT 28: Correlated Electrons: Low-dimensional Systems - Materials 2
TT 28.13: Talk
Wednesday, March 28, 2012, 18:15–18:30, H 0104
The anomalous metallic properties of quasi two-dimensional organic superconductors studied by non-linear transport — •Robert Rommel1, Benedikt Hartmann1, Jens Brandenburg1, John Schlueter2, and Jens Müller1 — 1Physikalisches Institut, Goethe-Universität, Frankfurt am Main — 2Argonne National Laboratory, Materials Science Division, Argonne, IL, USA
In ac transport measurements the technique of measuring higher harmonics, in particular the third (R3ω), may be used as an additional, powerful tool probing the microgeometry of the current distribution in a bulk sample. R3ω has been used, e.g., to determine the superconducting transition temperature of high-Tc cuprates or to estimate the number of correlated polarons in manganites. We apply this technique to the quasi two-dimensional organic charge-transfer salt κ-(H8-ET)2Cu[N(CN)2]Br and its fully deuterated analogue. We studied the dependence of R3ω on temperature, current, frequency, magnetic field and the degree of disorder and analyze the data with respect to the vicinity of the 1st order Mott metal-insulator transition line in the complex phase diagram of this class of materials. We show that the signal allows for an accurate determination of Tc (B) and found a good estimate for the upper critical magnetic field Bc2 of these extreme type-II superconductors. We furthermore gain information about changes in the transport mechanism, which we will discuss in terms of the anomalous properties of the metallic state in these materials.