Evolution of Entanglement for Two Atoms Interacting with a Thermal Field

Considering by means of nonpositivity of the partial transposition(NPT) and concurrence, the entanglement dynamic of two two-level atoms interacting with a single-mode optical field, which is prepared initially in the thermal state. The results show that entanglement of the atoms is very sensitive to the intrinsic decoherence coefficient and the photon number of cavity field. The evolution of NPT for the two atoms exhibits similar behaviors as that of their concurrence, and thus both are well-established measure of entanglement in such system.