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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 µ_B B ∼ k_B T, that may arise from Umklapp scattering. The second one is a plateau in the quantum critical regime, µ_B |B−B_c|<k_BT, where B_c 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.