Tuning the band structure and superconductivity in single-layer FeSe by interface engineering

• Published in: Nature communications Vol. 5; no. 1; p. 5044
• Main Authors: Peng, R, Xu, H C, Tan, S Y, Cao, H Y, Xia, M, Shen, X P, Huang, Z C, Wen, C H P, Song, Q, Zhang, T, Xie, B P, Gong, X G, Feng, D L
• Format: Journal Article
• Language: English
• Published: England Nature Publishing Group 26.09.2014
• Subjects: Electrons; Interfaces; Molecular beam epitaxy; Spectrum analysis; China
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/ncomms6044

The interface between transition metal compounds provides a rich playground for emergent phenomena. Recently, significantly enhanced superconductivity has been reported for single-layer FeSe on Nb-doped SrTiO3 substrate. Yet it remains mysterious how the interface affects the superconductivity. Here we use in situ angle-resolved photoemission spectroscopy to investigate various FeSe-based heterostructures grown by molecular beam epitaxy, and uncover that electronic correlations and superconducting gap-closing temperature (Tg) are tuned by interfacial effects. Tg up to 75 K is observed in extremely tensile-strained single-layer FeSe on Nb-doped BaTiO3, which sets a record high pairing temperature for both Fe-based superconductor and monolayer-thick films, providing a promising prospect on realizing more cost-effective superconducting device. Moreover, our results exclude the direct correlation between superconductivity and tensile strain or the energy of an interfacial phonon mode, and highlight the critical and non-trivial role of FeSe/oxide interface on the high Tg, which provides new clues for understanding its origin.