Anisotropic modulations of superconductivity in an isolated superconducting layer of the iron-based superconductor KCa2Fe4As4F2

Abstract

Iron-based superconductors exhibit multiple superconducting gaps opened in different energy bands. The debate surrounding their pairing mechanism stems from the diverse Fermi-surface topologies and orbital-dependent electronic correlations, raising questions about whether it belongs to weak-coupling scenarios or strong-coupling regimes based on short-range antiferromagnetic exchange interactions. In this paper, we present findings on angle-dependent modulations of superconductivity induced by local strains in the isolated topmost FeAs layer of KCa2Fe4As4F2. Leveraging scanning tunneling microscopy/spectroscopy, we observed significant variations in the superconducting gap depending on the orientation of the strain relative to the crystal lattice. This angle-dependent suppression of pairing strength in response to tiny tensile strains defies the explanation within weak-coupling scenarios. Instead, it can be qualitatively understood by considering the strain-induced symmetry-breaking distortion of the FeAs layer. These results provide compelling evidence that antiferromagnetic exchange interactions play a critical role in achieving high-temperature superconductivity in iron-based superconductors, challenging the prevailing assumptions about the nature of the pairing mechanism.

Source-reported materials — not catalogue approval

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