A pivotal challenge posed by unconventional superconductors is to unravel how superconductivity emerges upon cooling from the generally complex normal state. Here, we use nonlinear magnetic response, a probe that is uniquely sensitive to the superconducting precursor, to uncover remarkable universal behaviour in three distinct classes of oxide superconductors: strontium titanate, strontium ruthenate, and the cuprate high-Tc materials. We find unusual exponential temperature dependence of the diamagnetic response above the transition temperature Tc, with a characteristic temperature scale that strongly varies with Tc. We correlate this scale with the sensitivity of Tc to local stress and show that it is influenced by intentionally-induced structural disorder. The universal behaviour is therefore caused by intrinsic, self-organized structural inhomogeneity, inherent to the oxides’ perovskite-based structure. The prevalence of such inhomogeneity has far-reaching implications for the interpretation of electronic properties of perovskite-related oxides in general.
Bibliographical noteFunding Information:
We thank W. Zimmermann for the donation of the 3He fridge used (and for invaluable advice on its operation), A.S. Gibbs, C.W. Hicks and A.P. Mackenzie for providing the Sr2RuO4 samples, N. Bielinski for help in preparing the LSCO samples, S. Griffitt for assistance in constructing the susceptometer probes, A. Najev and M. Lukas for assistance with the uniaxial pressure measurements, and N. Barišić and B. Shklovskii for discussions. The work at the University of Minnesota was funded by the Department of Energy through the University of Minnesota Center for Quantum Materials under DESC-0016371.
© 2019, The Author(s).