Scanning tunneling microscopic observation of enhanced superconductivity in epitaxial Sn islands grown on SrTiO3 substrate

[Display omitted] Recent experimental and theoretical studies of single-layer FeSe film grown on SrTiO3 have revealed interface enhanced superconductivity, which opens up a pathway to promote the superconducting transition temperature. Here, to investigate the role of SrTiO3 substrate in epitaxial superconducting film, we grew a conventional superconductor β-Sn (bulk Tc ∼ 3.72 K) onto SrTiO3 substrate by molecular beam epitaxy. By employing scanning tunneling microscope and spectroscopic measurements, an enhanced Tc of 8.2 K is found for epitaxial β-Sn islands, deduced by fitting the temperature dependence of the gap values using the BCS formula. The observed interfacial charge injection and enhanced electron–phonon coupling are responsible for this Tc enhancement. Moreover, the critical field of 8.3 T exhibits a tremendous increase due to the suppression of the vortex formation. Therefore, the coexistence of enhanced superconductivity and high critical field of Sn islands demonstrates a feasible and effective route to improve the superconductivity by growing the islands of conventional superconductors on perovskite-type titanium oxide substrates.