DPG Phi
Verhandlungen
Verhandlungen
DPG

Berlin 2008 – scientific programme

Parts | Days | Selection | Search | Downloads | Help

TT: Fachverband Tiefe Temperaturen

TT 2: Symposium: High Magnetic Field Phenomena in Low Dimensional Magnets

TT 2.8: Talk

Monday, February 25, 2008, 12:45–13:00, H 0104

Diverging low-temperature thermal expansion of the spin-ladder system (C5H12N)2CuBr4 — •Thomas Lorenz1, Oliver Heyer1, Markus Garst2, Fabrizio Anfuso2, Achim Rosch2, Christian Rüegg3, and Karl Krämer41Institue of Physics II, University of Cologne, Germany — 2Institue of Theoretical Physics, University of Cologne, Germany — 3Centre for Nanotechnology and Dep. of Phys. and Astronomy, University College London, UK — 4Department of Chemistry and Biochemistry, University of Bern, Switzerland

The magnetic subsystem of piperidinium copper bromide (C5H12N)2CuBr4 represents a model system of an experimental realization of a two-leg spin-ladder Hamiltonian. Due to comparatively weak antiferromagnetic exchange couplings along the legs (≃ 12.9 K) and the rungs (≃ 3.6 K) of the ladders, two quantum phase transition are easily accessible in this compound: at Hc1≃ 6.8 T the gap closes and at Hc2≃ 13.9 T the field-polarized ferromagnetic state is reached. We present high-resolution measurements of the uniaxial thermal expansion and magnetostriction of (C5H12N)2CuBr4. For both quantities we observe pronounced anomalies arising from the pressure dependencies of the critical fields. The thermal expansion shows a very complex behavior with various sign changes and approaches a 1/√T divergence at the critical fields. All these low-temperature features are semi-quantitatively explained within a free fermion model; full quantitative agreement is obtained with Quantum Monte Carlo simulations.

Supported by the DFG through SFB 608.

100% | Mobile Layout | Deutsche Version | Contact/Imprint/Privacy
DPG-Physik > DPG-Verhandlungen > 2008 > Berlin