Nonequivalence of ensembles for long-range quantum spin systems in optical lattices
Date
2010
Authors
Kastner M.
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Abstract
Motivated by the anisotropic long-range nature of the interactions between cold dipolar atoms or molecules in an optical lattice, we study the anisotropic quantum Heisenberg model with Curie-Weiss-type long-range interactions. Absence of a heat bath in optical lattice experiments suggests a study of this model within the microcanonical ensemble. The microcanonical entropy is calculated analytically and nonequivalence of microcanonical and canonical ensembles is found for a range of anisotropy parameters. 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 differs. Qualitatively, the observed features of nonequivalent ensembles are expected to be relevant for long-range quantum spin systems realized in optical lattice experiments. © 2010 The American Physical Society.
Description
Keywords
Anisotropy parameters, Canonical ensemble, Heat bath, Heisenberg models, Long range interactions, Microcanonical ensembles, Microcanonical entropy, Microcanonical thermodynamics, Optical lattices, Quantum spin systems, Anisotropy, Crystal lattices, Ising model, Optical materials, Spin dynamics, Thermodynamics, Experiments
Citation
Physical Review Letters
104
24
104
24