The Misfit Strain Critical Point in the 3D Phase Diagrams of Cuprates

At the time of writing, data have been reported on several hundred different cuprate materials, of which a substantial fraction show superconductivity at temperatures as high as 130 K. The existence of several competing phases with comparable energy shows up in different ways in different materials, therefore it has not been possible to converge toward a universal theory for high-T (c) superconductivity. With the aim to find a unified description the Aeppli-Bianconi 3D phase diagram of cuprates has been proposed where the superlattice misfit strain eta is the third variable beyond doping delta and temperature T. The 3D phase diagrams for the magnetic order, and for the superconducting order extended to all cuprate families are described. We propose a formula able to describe the T (c) (delta,eta) surface, this permits to identify the stripe quantum critical point at delta (c)=1/8 and eta (c)=7% which is associated with the incommensurate to commensurate stripe phase transition, controlled by the misfit strain.