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Journal of Contemporary Physics (Armenian Academy of Sciences)

Magnetic properties and quantum entanglement on decorated zigzag ladder

L. Ananikyan, H. A. Lazaryan

Published Jul 7, 2011• 1 citation
Publisher

Abstract

Magnetic properties and quantum entanglement of Heisenberg model with two-, three- and four-site exchange interactions on zigzag ladder are studied. Magnetic properties and concurrence (measure of quantum entanglement) are analyzed by means of variational mean-field-like treatment based on the Gibbs-Bogoliubov inequality. The magnetization plateau and second-order phase transition are obtained. A comparison of the entanglement and magnetic characteristics for the zigzag ladder is made. Our calculations show that in the antiferromagnetic region the behavior of the concurrence coincides with that of the magnetization.

DOI
10.3103/s1068337211040104

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We consider the Heisenberg model with two-, and three-spin exchange interactions on a zigzag ladder in a strong magnetic field. Using the recursion method for the partition function in Ising approximation we have found exact results for the magnetization. We have shown the existence of magnetization plateaus in the case of mutual two-, and three-spin exchanges at low temperatures and different exchange parameters. The system exhibits different magnetic behaviors, depending on the values of the exchange parameters.
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The equilibrium magnetic and entanglement properties in a spin-1/2 Ising-Heisenberg model on a triangulated Kagomé lattice are analyzed by means of the effective field for the Gibbs-Bogoliubov inequality. The calculation is reduced to decoupled individual (clusters) trimers due to the separable character of the Ising-type exchange interactions between the Heisenberg trimers. The concurrence in terms of the three qubit isotropic Heisenberg model in the effective Ising field in the absence of a magnetic field is non-zero. The magnetic and entanglement properties exhibit common (plateau, peak) features driven by a magnetic field and (antiferromagnetic) exchange interaction. The (quantum) entangled and non-entangled phases can be exploited as a useful tool for signalling the quantum phase transitions and crossovers at finite temperatures. The critical temperature of order-disorder coincides with the threshold temperature of thermal entanglement.