Elastic Strains and Enhanced Critical Temperature in Copper-Oxide Superconductors

The influence of local strains on the critical temperature of the high- T c ceramic superconductors is analysed. The strong coupling between the elastic and superconducting behaviour, plus the short coherence length observed in these materials lead to the existence of regions where T c is significantly altered. These regions appear whenever the lattice is seriously distorted, like near dislocations or missing planes. Simple estimates, deduced from experimental data, show that a strong enhancement of T c close to lattice defects is to be expected.