Berlin 2015 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 18: Correlated Electrons: Spin Systems and Itinerant Magnets – Frustrated Magnets 2 (jointly with MA)
TT 18.12: Vortrag
Montag, 16. März 2015, 18:00–18:15, H 3005
High-temperature heat transport in coupled quantum spin chains — •Christian Hess1, Oleg Mityashkin1, Ashwin Mohan1, Chinnathambi Sekar1, Gernot Krabbes1, Bernd Büchner1, Romuald Saint-Martin2, and Alexandre Revcolevschi2 — 1Institute for Solid State Research, IFW Dresden, 01069 Dresden, Germany — 2Laboratoire de Physico-Chimie de L’Etat Solide, Université Paris-Sud, 91405 Orsay, France
We present high-temperature heat conductivity data up to T∼ J/2kB for the compounds SrCuO2 and CaCu2O3, which represent spin-1/2 realizations of the isotropic Heisenberg spin chain and of a weak-rung two-leg spin ladder, respectively. In both cases, the high-temperature heat conductivity is suppressed with increasing temperature, which indicates a thermally activated scattering process. Indeed, the analysis of the data reveals a perfect description of the temperature dependence of the mean free path lmag by just two scattering processes, viz. (i) a temperature independent scattering off boundaries that dominates at low temperature, and (ii) thermally activated high-temperature scattering lmag∼ exp(−T*/T). Interestingly, for the Heisenberg spin chain the energy scale kBT* of the activated scattering is comparable with typical phonon energies, suggestive of spinon-phonon scattering. However, in the weak-rung spin ladder, which can be viewed as a pair of weakly coupled spin chains, the energy scale of the activated scattering is clearly beyond the phonon energies in the system and kBT*∼ J. These findings suggest that the weak interchain coupling introduces a new, magnetic type of scattering.