Separate tuning of nematicity and spin fluctuations to unravel the origin of superconductivity in FeSe

Seung Ho Baek, Jong Mok Ok, Jun Sung Kim, Saicharan Aswartham, Igor Morozov, Dmitriy Chareev, Takahiro Urata, Katsumi Tanigaki, Yoichi Tanabe, Bernd Büchner, Dmitri V. Efremov

Research output: Contribution to journalArticlepeer-review

17 Citations (Scopus)


The interplay of orbital and spin degrees of freedom is the fundamental characteristic in numerous condensed matter phenomena, including high-temperature superconductivity, quantum spin liquids, and topological semimetals. In iron-based superconductors (FeSCs), this causes superconductivity to emerge in the vicinity of two other instabilities: nematic and magnetic. Unveiling the mutual relationship among nematic order, spin fluctuations, and superconductivity has been a major challenge for research in FeSCs, but it is still controversial. Here, by carrying out 77Se nuclear magnetic resonance (NMR) measurements on FeSe single crystals, doped by cobalt and sulfur that serve as control parameters, we demonstrate that the superconducting transition temperature Tc increases in proportion to the strength of spin fluctuations, while it is independent of the nematic transition temperature Tnem. Our observation therefore directly implies that superconductivity in FeSe is essentially driven by spin fluctuations in the intermediate coupling regime, while nematic fluctuations have a marginal impact on Tc.

Original languageEnglish
Article number8
Journalnpj Quantum Materials
Issue number1
Publication statusPublished - 2020 Dec 1
Externally publishedYes

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics


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