Enhanced superconductivity accompanying a Lifshitz transition in electron-doped FeSe monolayer

• Published in: Nature communications Vol. 8; no. 1; p. 14988
• Main Authors: Shi, X., Han, Z-Q, Peng, X-L, Richard, P., Qian, T., Wu, X-X, Qiu, M-W, Wang, S. C., Hu, J. P., Sun, Y-J, Ding, H.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 19-04-2017; Nature Publishing Group; Nature Portfolio
• Subjects: 639/766/119/1003; 639/766/119/544; Electrons; Humanities and Social Sciences; multidisciplinary; Physics; Potassium; Science; Science (multidisciplinary); Beijing China; China
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/ncomms14988

The origin of enhanced superconductivity over 50 K in the recently discovered FeSe monolayer films grown on SrTiO
3
(STO), as compared to 8 K in bulk FeSe, is intensely debated. As with the ferrochalcogenides A
x
Fe
2−
y
Se
2
and potassium-doped FeSe, which also have a relatively high-superconducting critical temperature (
T
c
), the Fermi surface (FS) of the FeSe/STO monolayer films is free of hole-like FS, suggesting that a Lifshitz transition by which these hole FSs vanish may help increasing
T
c
. However, the fundamental reasons explaining this increase of
T
c
remain unclear. Here we report a 15 K jump of
T
c
accompanying a second Lifshitz transition characterized by the emergence of an electron pocket at the Brillouin zone centre, which is triggered by high-electron doping following
in situ
deposition of potassium on FeSe/STO monolayer films. Our results suggest that the pairing interactions are orbital dependent in generating enhanced superconductivity in FeSe.
The origin of superconductivity enhancement in FeSe monolayer grown on SrTiO
3
compared to bulk FeSe is still a debated issue. Here, Shi
et al
. report a further 15 K jump of
T
c
accompanying a second Lifshitz transition triggered by electron doping in FeSe/SrTiO
3
monolayer films.