Regensburg 2010 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 10: Poster I

MA 10.77: Poster

Dienstag, 23. März 2010, 10:45–13:45, Poster A

Field and temperature dependence of spin and heat transport in dimerized spin 1/2 chains. — •Stephan Langer¹, Fabian Heidrich-Meisner¹, Rachid Darradi², and Wolfram Brenig² — ¹Physics Department, Arnold Sommerfeld Center for Theoretical Physics, and Center for NanoScience, LMU München, Germany — ²Institute for Theoretical Physics, Technical University of Braunschweig, Germany

We study the spin and heat conductivity of dimerized spin 1/2 chains in homogeneous magnetic fields at finite temperatures. Tuning the strength of the dimerization this model connects the limit of weakly coupled dimers to the Heisenberg chain. Our goal is to understand the dependence of heat and spin transport on the magnetic field, the temperature and the strength of dimerization. At zero temperature the model undergoes a field induced quantum phase transition from a dimerized into a Luttinger liquid phase. We search for signs of this transition in the spin and heat conductivity. Using exact diagonalization we calculate the Drude weights, the frequency dependence of the conductivities and the corresponding integrated spectral weights.

A similar transition from a gapped into a Luttinger Liquid phase is observed in spin ladder materials that have a comparably small exchange coupling, allowing experimentalists to probe transport at finite temperatures and fields. This serves as an additional motivation of our study.

This work is supported by the Deutsche Forschungsgemeinschaft via FOR 912.