A considerable enhancement of the superconducting transition temperature Tc in perovskite-type oxides is explained in the framework of the anharmonic model for superconductors with structurally unstable lattices. It is shown that the interaction of electrons with highly anharmonic oxygen-ion vibrations of a rotational type results in a sufficiently large coupling constant λ. The obtained estimation for Tc is in agreement with experimental data for La(Y)BaCuO systems.

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