Tuning the band structure and superconductivity in single-layer FeSe by interface engineering
01/11/14 15:45
The record of superconducting transition temperature (Tc) has long been 56 K for the
bulk iron-based high temperature superconductors. Recently, in single layer FeSe ontop of SrTiO3 substrate, much enhanced superconductivity with a pairing temperature up to 65K has been observed. However, it remains mysterious how the interface affects the superconductivity. Besides, it encourages further effort to increase the pairing temperature above the liquid nitrogen boiling temperature, so that more cost-effective applications could be expected.
By molecular beam epitaxy, we changed the interfacial oxide material to Nb:BaTiO3 [Fig.1(a)]. Superconducting gap closing temperature up to 75 K is observed in extremely tensile-strained single-layer FeSe on Nb-doped BaTiO3 [Fig.1(b)], 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. Besides, using in situ angle-resolved photoemission spectroscopy, we compared the electronic structure and superconducting gap of various FeSe-based heterostructures with different interfacial oxides, strain and thicknesses. We have uncovered that electronic correlations and superconducting gap-closing temperatures are tuned by interfacial effects. Moreover, our results exclude the direct relation between superconductivity and tensile strain, or the energy of an interfacial phonon mode, and demonstrate the crucial and non-trivial role of FeSe/oxide interface on the high pairing temperature [Fig.1(c)]. We speculate some possible interfacial interactions that mediate/facilitate Cooper pairing [Fig.1(d)]. These results yield new microscopic insights into the high Tc and provide clues for further enhancing Tc through interface engineering.
Reference：R. Peng, H. C. Xu, S. Y. Tan, H. Y. Cao, M. Xia, X. P. Shen, Z. C. Huang, C. H. P. Wen, Q. Song, T. Zhang, B. P. Xie, X. G. Gong, D. L. Feng, Tuning the band structure and superconductivity in single-layer FeSe by interface engineering, Nature Comm. 5, 5044 (2014).
bulk iron-based high temperature superconductors. Recently, in single layer FeSe ontop of SrTiO3 substrate, much enhanced superconductivity with a pairing temperature up to 65K has been observed. However, it remains mysterious how the interface affects the superconductivity. Besides, it encourages further effort to increase the pairing temperature above the liquid nitrogen boiling temperature, so that more cost-effective applications could be expected.
By molecular beam epitaxy, we changed the interfacial oxide material to Nb:BaTiO3 [Fig.1(a)]. Superconducting gap closing temperature up to 75 K is observed in extremely tensile-strained single-layer FeSe on Nb-doped BaTiO3 [Fig.1(b)], 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. Besides, using in situ angle-resolved photoemission spectroscopy, we compared the electronic structure and superconducting gap of various FeSe-based heterostructures with different interfacial oxides, strain and thicknesses. We have uncovered that electronic correlations and superconducting gap-closing temperatures are tuned by interfacial effects. Moreover, our results exclude the direct relation between superconductivity and tensile strain, or the energy of an interfacial phonon mode, and demonstrate the crucial and non-trivial role of FeSe/oxide interface on the high pairing temperature [Fig.1(c)]. We speculate some possible interfacial interactions that mediate/facilitate Cooper pairing [Fig.1(d)]. These results yield new microscopic insights into the high Tc and provide clues for further enhancing Tc through interface engineering.
Reference：R. Peng, H. C. Xu, S. Y. Tan, H. Y. Cao, M. Xia, X. P. Shen, Z. C. Huang, C. H. P. Wen, Q. Song, T. Zhang, B. P. Xie, X. G. Gong, D. L. Feng, Tuning the band structure and superconductivity in single-layer FeSe by interface engineering, Nature Comm. 5, 5044 (2014).