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arXiv · 2506.22435

Correlation Enhanced Electron-Phonon Coupling in FeSe/SrTiO$_3$ at a Magic Angle

Qiang Zou·Antik Sihi·Basu Dev Oli·Mercè Roig·Daniel Agterberg·Michael Weinert·Lian Li·Subhasish Mandal
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Abstract

While a predictive theory for unconventional superconductivity in Fe-based superconductors remains elusive, an extensively debated aspect is the interaction between phonons and strongly correlated electrons, and its potential role in the pairing mechanism. Here, through the combination of first principles dynamical mean field theory calculations and epitaxial growth of the single-layer FeX (X=Se, S, Te) on SrTiO$_3$ (STO)(001) substrate, which facilitates the controlled distortion of the FeX$_4$ tetrahedron, we demonstrate an unique superconducting dome where the superconducting gap peaks at a `magic' angle of the FeX$_4$ tetrahedron and the electron-phonon coupling (EPC) for the A$_{1g}$ mode is maximized for the FeSe film. Our findings uncover a significant role of electronic correlations in strengthening Cooper pairing in unconventional superconductors by enhancing EPC.

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Qiang Zou, Antik Sihi, Basu Dev Oli, Mercè Roig, Daniel Agterberg, Michael Weinert, Lian Li, Subhasish Mandal. 2025-06-27. Correlation Enhanced Electron-Phonon Coupling in FeSe/SrTiO$_3$ at a Magic Angle. https://arxiv.org/abs/2506.22435

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