Universal superconducting precursor in perovskite-based oxides

A pivotal challenge posed by unconventional superconductors is to unravel how superconductivity emerges upon cooling from the generally complex normal state. Some of the most prominent unconventional superconductors are oxides: strontium titanate, strontium ruthenate, and the cuprates exhibit greatly different superconducting transition temperatures T_c, and although their respective superconducting pairing mechanisms remain unknown, they are thought to differ as well. We use nonlinear magnetic response – a probe that is uniquely sensitive to the superconducting precursor – to uncover remarkable universal behavior in these three distinct classes of oxide superconductors [1]. We find an unusual exponential temperature dependence of the diamagnetic response above the transition temperature T_c, with a characteristic temperature scale that strongly varies with T_c. We correlate this scale with the sensitivity of T_c to local stress, indicating that the universal behavior is caused by intrinsic, self-organized structural inhomogeneity inherent to the oxides’ perovskite-based structure. Furthermore, the precursor can be strongly influenced by structural disorder, intentionally induced by uniaxial plastic deformation. The results show that structural inhomogeneity is prevalent in perovskite-related superconductors, with far-reaching implications for the interpretation of their electronic properties in general.

[1] D. Pelc et al., arxiv:1808.05763 (2018)