Condensed Matter Physics, 2009, vol. 12, No. 3, pp. 399-410

Title: Magnetocaloric effect in quantum spin-s chains
  A. Honecker (Institut für Theoretische Physik, Georg-August-Universität Göttingen, 37077 Göttingen, Germany),
  S. Wessel (Universität Stuttgart, Institut für Theoretische Physik III, Pfaffenwaldring 57, 70550 Stuttgart, Germany)

We compute the entropy of antiferromagnetic quantum spin-s chains in an external magnetic field using exact diagonalization and Quantum Monte Carlo simulations. The magnetocaloric effect, i. e., temperature variations during adiabatic field changes, can be derived from the isentropes. First, we focus on the example of the spin-s=1 chain and show that one can cool by closing the Haldane gap with a magnetic field. We then move to quantum spin-s chains and demonstrate linear scaling with s close to the saturation field. In passing, we propose a new method to compute many low-lying excited states using the Lanczos recursion.

Key words: quantum spin chains, magnetocaloric effect, entropy, exact diagonalization, Quantum Monte Carlo
PACS: 75.10.Pq, 75.30.Sg, 75.50.Ee, 02.70.-c
Comments: Figs. 6, Refs. 55, Tabs. 0

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