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.