Pair suppression caused by mosaic-twist defects in superconducting Sr 2 RuO 4 thin-films prepared using pulsed laser deposition

Sr 2 RuO 4 (SRO 214 ) 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 SRO 214 remains controversial. Solving this problem is massively impeded by the fact that superconducting SRO 214 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 SRO 214 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 Sr 3 Ru 2 O 7 (SRO 327 ). By systematically varying the SRO 214 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.