Enhanced superconductivity in FeSe/SrTiO${}_3$ from the combination of forward scattering phonons and spin fluctuations

Abstract

We study the effect of combining spin fluctuations and forward scattering electron-phonon ({\eph}) coupling on the superconductivity in the FeSe/SrTiO${}_3$ system modeled by a phenomenological two-band Hubbard model with long-range {\eph} interactions. We treat the electron and phonon degrees of freedom on an equal footing using a \emph{fully} self-consistent FLEX plus Migdal-Eliashberg calculation, which includes a self-consistent determination of the spin fluctuation spectrum. Based on FeSe monolayers, we focus on the case where one of the bands lies below the Fermi level (i.e. incipient), and demonstrate that the combined interactions can enhance or suppress $T_c$, depending on their relative strength. For a suitable choice of parameters, the spin-fluctuation mechanism yields a $T_c\approx 46.8$ K incipient $s_{\pm }$ superconductor, consistent with surface-doped FeSe thin films. A forward-focused {\eph} interaction further enhances the $T_c$, as observed in monolayer FeSe on SrTiO${}_3$.

11 pages, 5 figures

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Cited by in corpus (8)

• Evolution of spin excitations from bulk to monolayer FeSe
• Quantum geometric effect on Fulde-Ferrell-Larkin-Ovchinnikov superconductivity
• Superconductivity in monolayer FeSe enhanced by quantum geometry
• Direct probing of a large spin-orbit coupling in the FeSe superconducting monolayer on STO: Evidence for nontrivial topological states
• The phonon mechanism explanation of the superconductivity dichotomy between FeSe and FeS monolayers on STO and other substrates
• Direct evidence of a charge depletion region at the interface of Van der Waals monolayers and dielectric oxides: The case of superconducting FeSe/STO
• Superconductivity in the bilayer Hubbard model: Are two Fermi surfaces better than one?
• Temperature evolution of the Fermi surface of the FeSe monolayer on SrTiO${}_3$