Sudden death of entanglement of two atoms interacting with thermal fields

We investigate the entanglement dynamics of two initially entangled atoms each interacting with a thermal field. We show that the two entangled atoms become completely disentangled in a finite time and that the lost information cannot return to the atomic system when the mean photon number of the thermal field exceeds a critical value (3.3584), even though the whole system is lossless. Then we study how the detuning between the atomic transition frequency and the field frequency and the disparity between two coupling rates would affect the evolution of the entanglement of the atomic system.