Enhanced superconductivity accompanying a Lifshitz transition in electron-doped FeSe monolayer.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 28422183.
- Also identified by DOI 10.1038/ncomms14988 and PMC identifier 5399296.
- 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
The origin of enhanced superconductivity over 50 K in the recently discovered FeSe monolayer films grown on SrTiO<sub>3</sub> (STO), as compared to 8 K in bulk FeSe, is intensely debated. As with the ferrochalcogenides A<sub>x</sub>Fe<sub>2-y</sub>Se<sub>2</sub> and potassium-doped FeSe, which also have a relatively high-superconducting critical temperature (T<sub>c</sub>), 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<sub>c</sub>. However, the fundamental reasons explaining this increase of T<sub>c</sub> remain unclear. Here we report a 15 K jump of T<sub>c</sub> 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.