Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe

TT: Fachverband Tiefe Temperaturen

TT 27: CE: Poster Session

TT 27.69: Poster

Mittwoch, 24. März 2010, 14:00–18:00, Poster D1

Spinon localization in the heat transport of the spin-1/2 ladder compound (C₅H₁₂N)₂CuBr₄ — •Gerhard Kolland¹, Jens Rohrkamp¹, Beni Thielemann², Henrik M. Ronnow³, Christian Rüegg⁴, Karl Krämer⁵, John A. Mydosh¹, Alexandr V. Sologubenko¹, and Thomas Lorenz¹ — ¹II. Physikalisches Institut, Universität zu Köln, Germany — ²Lab. for Neutron Scattering, ETH Zürich & PSI Villigen, Switzerland — ³Lab. for Quantum Magnetism, EPFL, Switzerland — ⁴London Centre for Nanotech. and Dep. of Phys. and Astron., University College London, UK — ⁵Dep. of Chem. and Biochem., University of Bern, Switzerland

Piperidium copper bromide (C₅H₁₂N)₂CuBr₄ is a two-leg spin-1/2 ladder system with comparatively weak antiferromagnetic exchange couplings along the legs and the rungs. Hence, this system has two experimentally accessible quantum phase transitions; from a gapped spin-singlet state to a gappless Luttinger-liquid state at H_c1≃ 7 T and from this state to a fully polarized state at H_c2≃ 14 T. Here, we present experiments on the magnetic field-dependent thermal transport. The thermal conductivity is only weakly affected by the field-induced transitions at H_c1/c2, suggesting the absence of a direct contribution of the spin excitations to the heat transport. We observe, however, that the thermal conductivity is suppressed by the magnetic field deeply within the Luttinger-liquid state. These surprising observations are discussed in terms of localization of spinons within finite ladder segments and spinon-phonon umklapp scattering of the predominantly phononic heat transport.Supported by the DFG through SFB 608.