Martin Greven, University of Minnesota

Jeudi 10 octrobre 2019, 14h00, salle Nobelium

Unusual Emergence of Superconductivity in Complex Oxides

Superconductivity has been a major research topic for more than a century, yet in many important materials this macroscopic quantum phenomenon remains poorly understood. We recently uncovered that superconductivity emerges in an unusual, yet remarkably universal manner upon cooling in three well-known families of complex oxides – the cuprates, strontium titanate, and strontium ruthenate – for which the origin of superconductivity is thought to differ [1]. This breakthrough was enabled by nonlinear magnetic response measurements, an innovative experimental approach that is uniquely sensitive to superconducting fluctuations. We find that the diamagnetic response above the bulk critical temperature Tc exhibits exponential temperature dependence, with a characteristic temperature scale that strongly varies with Tc. This scale correlates with the sensitivity of Tc to local stress, and it is influenced by intentionally-induced structural disorder. The universal behavior therefore is 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, including thin films and heterostructures. In the case of the cuprates, this inherent inhomogeneity constitutes a pivotal part of a phenomenological model that comprehensively captures hitherto elusive properties of the normal and superconducting states [2].

[1] D. Pelc et al., Nat. Commun. 10, 2729 (2019)
[2] D. Pelc et al., Sci. Adv. 5, eaau4538 (2019)

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