Regensburg 2010 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 12: CE: Metal-Insulator Transition 1
TT 12.6: Talk
Tuesday, March 23, 2010, 10:45–11:00, H19
Disorder enhanced fluctuations in κ-(D8-ET)2Cu[N(CN)2]Br — •Jens Brandenburg1, Jens Müller2, Steffen Wirth1, and John A. Schlueter3 — 1Max-Planck-Insitut für Chemische Physik fester Stoffe, Dresden — 2Goethe-Universität Frankfurt am Main — 3Argonne National Laboratory, Argonne, IL, USA
The way in which disorder influences the electronic properties in strongly correlated systems is an intriguing question in modern condensed matter physics. Here, we report on fluctuation spectroscopy studies of the organic charge transfer salt κ-(D8-ET)2Cu[N(CN)2]Br. The degree of intrinsic disorder in this quasi-2D conductor can be tuned by varying the cooling rate at the structural glass-like transition around Tg ≃ 75 K [1]. We compare data taken after slow (0.05 K/min) and fast (5 K/min) cooling. Larger cooling rates increase the amount of disorder and therefore enhance the resistance fluctuations. The total noise power originating from the vibrational degrees of freedom of the ET molecules [2] is about 25% higher for the faster cooling rate. In addition, our experiments reveal another contribution to the resistance noise. Since κ-(D8-ET)2Cu[N(CN)2]Br is very close to a Mott metal-to-insulator transition the coexistence of electronic correlations and disorder may result in the formation of a so-called soft Hubbard gap in the DOS due to localization effects.
[1] N. Toyota, M. Lang, and J. Müller, Low-Dimensional Molecular Metals, Springer (2007)
[2] J. Müller et al., Phys. Rev. B 79, 214521 (2009)