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Lieb-Mattis Model for Two Interpenetrating Antiferromagnets

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Schmalfuss D., Krüger S., Richter J.

Acta Physica Polonica A

2000

vol. 97

issue 3

377-380

We investigate a frustrated Lieb-Mattis-like spin-1/2 model that is a reference model for the corresponding square-lattice Heisenberg model describing the unusual magnetic properties of Ba_{2}Cu_{3}O_{4}Cl_{2}. Due to frustration we obtain a rich magnetic phase diagram. We find two critical temperatures in accordance with recent experiments on Ba_{2}Cu_{3}O_{4}Cl_{2}.

Diagonalization of a Bosonic Quadratic Form Using CCM: Application on a System with Two Interpenetrating Square Lattice Antiferromagnets

100%

Krüger S., Schmalfuss D., Richter J.

Acta Physica Polonica A

2000

vol. 97

issue 5

951-954

While the diagonalization of a quadratic bosonic form can always be done using a Bogolyubov transformation, the practical implementation for systems with a large number of different bosons is a tedious analytical task. Here we use the coupled cluster method to exactly diagonalise such complicated quadratic forms. This yields to a straightforward algorithm which can easily be implemented using computer algebra even for a large number of different bosons. We apply this method on a Heisenberg system with two interpenetrating square lattice antiferromagnets, which is a model for the quasi-2D antiferromagnet Ba_{2}Cu_{3}O_{4}Cl_{2}. Using a four-magnon spin wave approximation we get a complicated Hamiltonian with four different bosons, which is treated with coupled cluster method. Results are presented for magnetic ground state correlations.

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2 Acta Physica Polonica A

2 2000

2 Krüger S.

2 Richter J.

2 Schmalfuss D.

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Lieb-Mattis Model for Two Interpenetrating Antiferromagnets

Diagonalization of a Bosonic Quadratic Form Using CCM: Application on a System with Two Interpenetrating Square Lattice Antiferromagnets