Onofre Rojas, M Rojas, N. S. Ananikian, S. M. de Souza
Most of the quantum entanglement investigations are focussed on two-qubits or some finite (small) chain structure, since the infinite chain structure is considerably a cumbersome task. Therefore, the quantum entanglement properties involving an infinite chain structure is quite important, not only because the mathematical calculation is cumbersome but also because real materials are well represented by infinite chain. Thus, in this paper we consider entangled diamond chain with Ising and anisotropic Heisenberg (Ising-XXZ) coupling. Two interstitial particles are coupled through Heisenberg coupling or simply two-qubit Heisenberg, which could be responsible for the emergence of entanglement. These two-qubit Heisenberg operators are interacted with two nodal Ising spins. An infinitely diamond chain is organized by interstitial- interstitial and nodal-interstitial (dimer-monomer) sites couplings. We are able to get the thermal average of two-qubit operator, called the reduced two-qubit density operator. Since these density operators are spatially separated, we could obtain the concurrence (entanglement) directly in the thermodynamic limit. The thermal entanglement (concurrence) is constructed for different values of anisotropic Heisenberg parameter, magnetic field and temperature. We also observed the threshold temperature via the parameter of anisotropy, Heisenberg and Ising interaction, external magnetic field and temperature.
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http://arxiv.org/abs/1210.0596
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