Pair suppression caused by mosaic-twist defects in superconducting Sr₂RuO₄ thin-films prepared using pulsed laser deposition

Abstract

Sr₂RuO₄ (SRO₂₁₄) is a prototypical unconventional superconductor. However, since the discovery of its superconductivity a quarter of a century ago, the symmetry of the bulk and surface superconducting states in single crystal SRO₂₁₄ remains controversial. Solving this problem is massively impeded by the fact that superconducting SRO₂₁₄ is extremely challenging to achieve in thin-films as structural defects and impurities sensitively annihilate superconductivity. Here we report a protocol for the reliable growth of superconducting SRO₂₁₄ thin-films by pulsed laser deposition and identify universal materials properties that are destructive to the superconducting state. We demonstrate that careful control of the starting material is essential in order to achieve superconductivity and use a single crystal target of Sr₃Ru₂O₇ (SRO₃₂₇). By systematically varying the SRO₂₁₄ film thickness, we identify mosaic twist as the key in-plane defect that suppresses superconductivity. The results are central to the development of unconventional superconductivity.