Along with some other researches we have realised that the true origin of high-temperature superconductivity should be found in the strong Coulomb repulsion combined with a significant electronphonon interaction. Both interactions are strong (on the order of 1 eV) compared with the low Fermi energy of doped carries which makes the conventional BCS-Eliashberg theory inapplicable in cuprates and related doped insulators. Based on our recent analytical and numerical results I argue that high-temperature superconductivity from repulsion is impossible for any strength of the Coulomb interaction. Major steps of our alternative polaronic theory are outlined starting from the generic Hamiltonian with the unscreened (bare) Coulomb and electron-phonon interactions accounting for critical temperatures of high-temperature superconductors without any adjustable parameters.
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