Scanning tunnelling spectroscopy of superconductivity on surfaces of LiTi<sub>2</sub>O<sub>4</sub>(111) thin films.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 28671187.
- Also identified by DOI 10.1038/ncomms15975 and PMC identifier 5500876.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
Unique superconductivity at surfaces/interfaces, as exemplified by LaAlO<sub>3</sub>/SrTiO<sub>3</sub> interfaces, and the high transition temperature in ultrathin FeSe films, have triggered intense debates on how superconductivity is affected in atomic and electronic reconstructions. The surface of superconducting cubic spinel oxide LiTi<sub>2</sub>O<sub>4</sub> is another interesting system because its inherent surface electronic and atomic reconstructions add complexity to superconducting properties. Investigations of such surfaces are hampered by the lack of single crystals or high-quality thin films. Here, using low-temperature scanning tunnelling microscopy and spectroscopy, we report an unexpected small superconducting energy gap and a long coherence length on the surface of LiTi<sub>2</sub>O<sub>4</sub>(111) epitaxial thin films. Furthermore, we find that a pseudogap opening at the Fermi energy modifies the surface superconductivity. Our results open an avenue for exploring anomalous superconductivity on the surface of cubic transition-metal oxides, where the electronic states are spontaneously modulated involving rich many-body interactions.