Inhomogeneity in complex oxide superconductors

Some of the most studied unconventional superconductors, including the cuprate high-Tc materials, are oxides. In this talk, I will present some fresh insights into the physics of oxide superconductors, obtained with the help of two somewhat unusual experimental techniques - nonlinear magnetic response and uniaxial pressure. In particular, I will show that several very different complex oxides have the same superconducting precursor regime above the macroscopic transition temperature, Tc. This universal feature turns out to be related to subtle structural inhomogeneity shared by the different materials. Furthermore, we find that it is possible to manipulate this inhomogeneity by plastic deformation of the samples, in experiments that open up a new avenue in the study of unconventional superconductors. Finally, I will present some preliminary results on the intriguing effects of deformation and annealing on Tc in cuprates and strontium titanate.