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arXiv · 1005.5050

Nonequivalence of ensembles in the Curie-Weiss anisotropic quantum Heisenberg model

Michael Kastner
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Abstract

The microcanonical entropy s(e,m) as a function of the energy e and the magnetization m is computed analytically for the anisotropic quantum Heisenberg model with Curie-Weiss-type interactions. The result shows a number of interesting properties which are peculiar to long-range interacting systems, including nonequivalence of ensembles and partial equivalence. Furthermore, from the shape of the entropy it follows that the Curie-Weiss Heisenberg model is indistinguishable from the Curie-Weiss Ising model in canonical thermodynamics, although their microcanonical thermodynamics in general differs. The possibility of experimentally realizing quantum spin models with long-range interactions in a microcanonical setting by means of cold dipolar gases in optical lattices is discussed.

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Michael Kastner. 2010-07-01. Nonequivalence of ensembles in the Curie-Weiss anisotropic quantum Heisenberg model. https://doi.org/10.1088/1742-5468%2F2010%2F07%2Fp07006

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