  The dynamical evolution of a quantum system composed of two coupled cavities,
each containing a two-level atom and a single-mode thermal field, is
investigated under different conditions. The entanglement between the two atoms
is controlled by the hopping strength and the detuning between the atomic
transition and the cavities. We find that when the atomic transition is far
off-resonant with both the eigenmodes of the coupled cavity system, the
maximally entangled state for the two atoms can be generated with the initial
state in which one atom is in the ground state and the other is in the excited
state. When both the two atoms are initially in the excited state, the
entanglement exhibits period sudden birth and death. By choosing appropriate
parameter values, the initial maximal entanglement of the two atoms can be
frozen. The relation between the concurrence and cooperative parameter is
calculated.
