2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/27920A model of superconductivity is proposed taking into account repulsive particle interaction, mesoscopic phase separation and softening of crystalline lattice. These features are typical of many high-temperature superconductors. The main results obtained for the model are: (i) phase separation is possible only if repulsive forces play a significant role; (ii) the critical temperature as a function of the superconducting phase fraction can have non-monotonic behaviour; (iii) superconductivity is possible in heterophase systems even when it would be forbidden in pure samples. These results are in agreement with experiments.1 file, 20 pages, RevTex, no figuresSuperconductivitytext