Regensburg 2007 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 18: Spindependent Transport II
MA 18.13: Vortrag
Mittwoch, 28. März 2007, 18:15–18:30, H22
Magnetothermal transport in the spin-1/2 chains of copper pyrazine dinitrate — •Alexandr V. Sologubenko1, Kai Berggold1, Thomas Lorenz1, Achim Rosch2, Efrat Shimshoni3, Matt D. Phillips4, and Mark M. Turnbull4 — 1II. Physikalisches Institut, Universität zu Köln, 50937 Köln, Germany — 2Institut für Theoretische Physik, Universität zu Köln, 50937 Köln, Germany — 3Department of Mathematics–Physics, University of Haifa at Oranim, Tivon 36006, Israel — 4Carlson School of Chemistry and Department of Physics, Clark University, Worcester, MA 01610
We present experiments on the thermal transport in the spin-1/2 chain compound copper pyrazine dinitrate Cu(C4H4N2)(NO3)2. The heat conductivity shows a surprisingly strong dependence on the applied magnetic field B, characterized at low temperatures by two main features. The first one appearing at low B is a characteristic dip located at µB B ∼ kB T, that may arise from Umklapp scattering. The second one is a plateau in the quantum critical regime, µB |B−Bc|<kBT, where Bc is the saturation field at T=0. The latter feature clearly points towards a momentum and field independent mean free path of the spin excitations, contrary to theoretical expectations.
Supported by the Deutsche Forschungsgemeinschaft through SFB 608.