Unraveling Enhanced Superconductivity in Single-Layer FeSe through Substrate Surface Terminations.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 40899338.
- Also identified by DOI 10.1021/acs.nanolett.5c01298 and PMC identifier 12670505.
- 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
Single-layer FeSe on SrTiO<sub>3</sub>(001) substrates shows a superconducting transition temperature much higher than that of bulk FeSe, which has been attributed to factors such as electron doping, interfacial electron-phonon coupling, and electron correlations. To pinpoint the primary driver, we grew single-layer FeSe films on SrTiO<sub>3</sub>(001) substrates with coexisting TiO<sub>2</sub> and SrO surface terminations. Scanning tunneling spectroscopy revealed a larger superconducting gap (17.0 meV) on the TiO<sub>2</sub>-termination than on the SrO-termination (10.5 meV). Tunneling spectroscopy also showed a larger work function on the SrO surface, resulting in reduced charge transfer to FeSe, as confirmed by angle-resolved photoemission spectroscopy. Scanning transmission electron microscopy further revealed distinctive interfacial atomic-scale structures, with the Se-Fe-Se tetrahedral angle changing from 109.5° on the SrO-termination to 104.9° on the TiO<sub>2</sub>-termination. Compared to dynamical mean field theory calculations, our results indicate that enhanced superconductivity in single-layer FeSe/TiO<sub>2</sub> arises from optimal electron correlations, in addition to sufficient charge transfer from the substrate.