Figure 2: Lower panel: spin-gap energy as a function of misfit strain , normalized to the critical values of the 1/8 phase, in different superconducting cuprates at optimum doping. Upper panel: the superconducting critical temperature as a function of the misfit strain at constant doping (1/8) and the Wigner polaron crystal in Nd doped La214 cuprate perovskites. The structural transition from at high misfit strain is indicated.