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Effects of a strict site-occupation constraint in the
description of quantum spin systems at finite temperature

Abstract : We study quantum spin systems described by Heisenberg-like models at finite
temperature with a strict site-occupation constraint imposed by a procedure
originally proposed by V. N. Popov and S. A. Fedotov. We show that the strict
site-occupation constraint modifies quantitatively the behaviour of physical
quantities when compared to the case for which this constraint is fixed in the
average by means of a Lagrange multiplier method. The relevance of the Neel
state with the strict site-occupation contraint of the spin lattice is studied.
With an exact site-occupation the transition temperature of the
antiferromagnetic Neel and spin liquid order parameters are twice as large
as the critical temperature one gets with an average Lagrange multiplier
method. We consider also a mapping of the low-energy spin Hamiltonian into a
QED3 Lagrangian of spinons. In this framework we compare the dynamically
generated mass to the one obtained by means of an average site-occupation
constraint.
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Contributor : Raoul Dillenschneider <>
Submitted on : Tuesday, February 6, 2007 - 8:43:36 AM
Last modification on : Thursday, April 23, 2020 - 2:26:25 PM
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Raoul Dillenschneider. Effects of a strict site-occupation constraint in the
description of quantum spin systems at finite temperature. Mathematical Physics [math-ph]. Université Louis Pasteur - Strasbourg I, 2006. English. ⟨tel-00129129⟩

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