Epitaxial stabilization of an orthorhombic Mg-Ti-O superconductor

The titanium oxide superconductors exhibit many intriguing phenomena analogous to cuprates and iron pnictides/chalcogenides thus provide an ideal platform for studying the pairing mechanism of high-temperature superconductors. Here we report fabrication superconducting Mg-Ti-O films on ${\mathrm{MgAl}}_{2}{\mathrm{O}}_{4}$ substrates with three principal orientations by ablating a ${\mathrm{MgTi}}_{2}{\mathrm{O}}_{4}$ target. Strikingly, single-crystalline film unexpected structure has been found (011)-oriented substrate, zero resistance transition temperature (${T}_{\mathrm{c}0}$) up 5.0 K which is highest among orientations. Compositional structural characterizations confirm that highly reduced Mg/Ti ratio orthorhombic ${\mathrm{Ti}}_{9}{\mathrm{O}}_{10}$-like (denoted as Mg: ${\mathrm{Ti}}_{9}{\mathrm{O}}_{10}$). Such unstable in bulk but favorable (011)-surface due interfacial strain. Similar other oxides, ${\mathrm{Ti}}_{9}{\mathrm{O}}_{10}$ exhibits relatively large quasi-isotropic upper critical field (${B}_{\mathrm{c}2}\ensuremath{\sim}13.7$ T). similarity points common origin superconductivity family, providing valuable insights unconventional metal compounds.