Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

International Journal of Modern Physics B

FINITE TEMPERATURE RESULTS FROM CONSTRAINED FERMIONIZATION IN THE 2-D SPIN 1/2 HEISENBERG ANTIFERROMAGNET I: THE NÉEL PHASE

Mario Di Stasio, A. Tagliacozzo, Elisa Ercolessi, G. Morandi

Published Mar 15, 1994• 4 citations
Publisher

Abstract

The antiferromagnetic saddle point is studied up to one-loop corrections, including, within the same approximation, the constraint of single site occupancy in the fermionization procedure, at all temperatures. The resulting spin wave spectrum and zero point fluctuations are the same as those of the spin wave theory. The effect of the constraint on the temperature dependence of the specific heat is discussed.

DOI
10.1142/s0217979294000294

Related papers

FINITE TEMPERATURE RESULTS FROM CONSTRAINED FERMIONIZATION IN THE 2-D SPIN 1/2 HEISENBERG ANTIFERROMAGNET II: FLUCTUATIONS IN THE DIMER PHASES

Mario Di Stasio, A. Tagliacozzo, Elisa Ercolessi +1 more

The constraint of single-site occupancy is implemented in the fermionization of the model, within the saddle point approximation. The columnar and the staggered dimer phases are studied and the contribution of the fluctuations to the zero point energy and the specific heat is analyzed.

International Journal of Modern Physics B•Mar 15, 1994•2 citations

Ordered Phase in the Fermionized Heisenberg Antiferromagnet

S. Azakov, M. Dilaver, Oztas, A. M.

Thermal properties of the ordered phase of the spin 1/2 isotropic Heisenberg Antiferromagnet on a d-dimensional hypercubical lattice are studied within the fermionic representation when the constraint of single occupancy condition is taken into account by the method suggested by Popov and Fedotov. Using saddle point approximation in path integral approach we discuss not only the leading order but also the fluctuations around the saddle point at one-loop level. The influence of taking into account the single occupancy condition is discussed at all steps.

arXiv:cond-mat/9903379•Mar 25, 1999•0 citations

Fluctuations around the magnetic and nonmagnetic saddle points in the two-dimensional spin-1/2 frustrated Heisenberg model

Mario Di Stasio, Elisa Ercolessi, G. Morandi +1 more

Fermionization of the spin operators is allowed only in the restricted Hilbert space of singly occupied sites. A method to implement this single-site occupancy constraint is applied to the frustrated Heisenberg model. This method allows us to study either magnetic or nonmagnetic phases at finite temperatures. A quantitative estimate of the relative weight of quantum fluctuations around the disordered dimer phases and the antiferromagnetic phase is given.

Physical review. B, Condensed matter•Apr 15, 1994•1 citation

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

Raoul Dillenschneider

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.

•Sep 8, 2006•0 citations

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

Raoul Dillenschneider

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 \cite{Popov-88}. 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 Néel state with the strict site-occupation contraint of the spin lattice is studied. With an exact site-occupation the transition temperature of the antiferromagnetic Néel 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 $QED_3$ Lagrangian of spinons. In this framework we compare the dynamically generated mass to the one obtained by means of an average site-occupation constraint.

arXiv:cond-mat/0609239•Sep 11, 2006•0 citations

SINGLE SITE-OCCUPANCY CONSTRAINT FOR THE HUBBARD MODEL AT FINITE TEMPERATURE

Mario Di Stasio, Elisa Ercolessi, G. Morandi +2 more

We show how it is possible to include the constraint of single site-occupancy in the large U limit of the Hubbard model at half-filling by means of a local chemical potential. The formalism which is in principle exact allows for finite temperature mean field results satisfying the constraint within 10%. The method is here applied to the dimerized phase and the commensurate flux phase which are still found as local saddle points of the action. The symmetry properties of these actions have been studied. One loop static corrections have been added to obtain an effective free energy and an estimate of the specific heat. In the limit of zero temperature our results reproduce those of the conventional mean field theory of these phases, because quantum fluctuations have not been included. We find that the temperature destabilizes the flux phase more than it does with the dimer phase, especially due to the constraint, which does not suppress phase fluctuating modes, provided the flux is conserved.

International Journal of Modern Physics B•Aug 15, 1993•5 citations
The antiferromagnetic saddle point is studied up to one-loop corrections, including, within the same approximation, the constraint of single site occupancy in the fermionization procedure, at all temperatures. The resulting spin wave spectrum and zero point fluctuations are the same as those of the spin wave theory. The effect of the constraint on the temperature dependence of the specific heat is discussed.
Thermal properties of the ordered phase of the spin 1/2 isotropic Heisenberg Antiferromagnet on a d-dimensional hypercubical lattice are studied within the fermionic representation when the constraint of single occupancy condition is taken into account by the method suggested by Popov and Fedotov. Using saddle point approximation in path integral approach we discuss not only the leading order but also the fluctuations around the saddle point at one-loop level. The influence of taking into account the single occupancy condition is discussed at all steps.
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.
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 \cite{Popov-88}. 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 Néel state with the strict site-occupation contraint of the spin lattice is studied. With an exact site-occupation the transition temperature of the antiferromagnetic Néel 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 QED3QED_3QED3​ Lagrangian of spinons. In this framework we compare the dynamically generated mass to the one obtained by means of an average site-occupation constraint.
We show how it is possible to include the constraint of single site-occupancy in the large U limit of the Hubbard model at half-filling by means of a local chemical potential. The formalism which is in principle exact allows for finite temperature mean field results satisfying the constraint within 10%. The method is here applied to the dimerized phase and the commensurate flux phase which are still found as local saddle points of the action. The symmetry properties of these actions have been studied. One loop static corrections have been added to obtain an effective free energy and an estimate of the specific heat. In the limit of zero temperature our results reproduce those of the conventional mean field theory of these phases, because quantum fluctuations have not been included. We find that the temperature destabilizes the flux phase more than it does with the dimer phase, especially due to the constraint, which does not suppress phase fluctuating modes, provided the flux is conserved.