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

Abstract

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.

20 pages, 3 figures; includes supplementary materials (1 note and 3 figures)

References in corpus (7)

• Magnetism, superconductivity, and pairing symmetry in Fe-based superconductors
• Why Does Undoped FeSe Become A High Tc Superconductor Under Pressure?
• Orbital-driven nematicity in FeSe
• Enhancement of superconductivity near a nematic quantum critical point
• Nematicity, magnetism and superconductivity in FeSe
• NMR evidence for static local nematicity and its cooperative interplay with low-energy magnetic fluctuations in FeSe under pressure
• ${}^{77}$Se-NMR Study under Pressure on 12%-S Doped FeSe

Cited by in corpus (3)

• On the Remarkable Superconductivity of FeSe and its Close Cousins
• Eliashberg theory for spin-fluctuations mediated superconductivity -- Application to bulk and monolayer FeSe
• Impact of Nematicity on the Relationship between Antiferromagnetic Fluctuations and Superconductivity in FeSe0.91S0.09 Under Pressure