Thermal entanglement in an exactly solvable Ising-XXZ diamond chain structure

摘要

Most quantum entanglement investigations are focused on two qubits or some finite (small) chain structure,nsince the infinite chain structure is a considerably cumbersome task. Therefore, the quantum entanglementnproperties involving an infinite chain structure is quite important, not only because the mathematical calculationnis cumbersome but also because real materials are well represented by an infinite chain. Thus, in this papernwe consider an entangled diamond chain with Ising and anisotropic Heisenberg (Ising-XXZ) coupling. Twoninterstitial particles are coupled through Heisenberg coupling or simply two-qubit Heisenberg, which couldnbe responsible for the emergence of entanglement. These two-qubit Heisenberg operators are interacted withntwo nodal Ising spins. An infinite diamond chain is organized by interstitial-interstitial and nodal-interstitialn(dimer-monomer) site couplings. We are able to get the thermal average of the two-qubit operator, called thenreduced two-qubit density operator. Since these density operators are spatially separated, we could obtain thenconcurrence (entanglement) directly in the thermodynamic limit. The thermal entanglement (concurrence) isnconstructed for different values of the anisotropic Heisenberg parameter, magnetic field, and temperature. Wenalso observed the threshold temperature via the parameter of anisotropy, Heisenberg and Ising interaction, externalnmagnetic field, and temperature.