Thermal entanglement of two atoms with dipole-dipole and Ising interactions

In this paper, we investigated the entanglement dynamics between two two-level natural or artificial atoms interacting with a thermal one-mode field of lossless cavity taking into account the direct dipole-dipole and Ising coupling. We obtained the exact solution for time-dependent density matrix and calculated atom-atom negativity. The results showed that for dipole-uncoupled atoms and resonant atoms-field interaction the entanglement greatly enhances with Ising coupling increasing. In contrast, for model with non-zero detuning the Ising coupling has almost no effect on the degree of entanglement. We also derived that for resonant interaction and dipole-coupled atoms the anti-Ferromagnetic coupling produces a slightly higher degree of entanglement in comparison with the Ferromagnetic coupling. For entangled initial atomic states we obtained that Ising coupling interaction has effect on entanglement behavior only for a model with large detuning values.