Multiband full-bandwidth anisotropic Eliashberg theory of interfacial electron-phonon coupling and high-Tc superconductivity in FeSe/SrTiO3

We examine the impact of interfacial phonons on the superconducting state of FeSe/SrTiO3 developing a material's specific multiband, full bandwidth, and anisotropic Eliashberg theory for this system. Our self-consistent calculations highlight the importance of the interfacial electron-phonon interaction, which is hidden behind the seemingly weak-coupling constant lambda(m) = 0.4, in mediating the high T-c, and explain other puzzling experimental observations, such as the s-wave symmetry and replica bands. We discover that the formation of replica bands has a T-c decreasing effect that is nevertheless compensated by deep Fermi-sea Cooper pairing which has a T-c enhancing effect. We predict a strong-coupling dip-hump signature in the tunneling spectra due to the interfacial coupling.