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Abstract
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In this paper, we consider a Hamiltonian model that includes interaction of two coupled
two-level atoms with a single-mode quantized electromagnetic field in a cavity via the
degenerate two-photon transition. The cavity is filled with a Kerr-like medium and is held at
a temperature T . The free field Hamiltonian possesses the su(1, 1) symmetry which realized
by either even or odd photon-number states. The total number of excitation as a constant of
motion, provides a decomposition of the Hilbert space of system into direct sums of invariant
subspaces. As a results, the representation of the Hamiltonian becomes block-diagonal
matrix with three blocks. After diagonalizing each block, we obtain thermal state of system
in the whole Hilbert space and within its excitation subspaces. Finally, the effect of temperature,
atom-atom and Kerr-type couplings on the degree of thermal entanglement between
the atoms are investigated. Our results show that within the single-excitation subspace
spanned with odd photon-number states, the entanglement between the atoms is thermally
robust.
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