Quantum oscillations in superconducting Sr₂RuO₄ thin films grown by molecular beam epitaxy

Sr₂RuO₄ had an eventful past, lingering between an insulating, strongly correlated antiferromagnetic spin system and a low-temperature Fermi liquid superconductor. Moreover, the long-standing problem on the superconducting order parameter has been solved recently, demanding a reassessment of the intrinsic electronic structure of this material using well-defined specimens. Here, superconducting thin films of the low-temperature superconductor Sr₂RuO₄ were grown by molecular beam epitaxy. The highest superconducting transition temperature was 1.4 K and those films showed a residual-resistivity ratio (RRR) of 114. High magnetic field (up to 24 T) magneto-resistance measurements above 0.5 K show Shubnikov-de Haas oscillations thus allowing us to study the intrinsic electronic structure of this material along with the influence of in-plane epitaxial strain in comparison to bulk samples. We also assessed the temperature dependence of the Hall effect of these samples and confirmed that for superconducting samples with RRR > 50, the sign of the Hall coefficient changes twice (130 K and 30 K) and the sign change at 30 K is driven by impurity scattering. In contrast, samples with RRR< 50 show a negative Hall coefficient below 300 K.