Large electron–phonon interactions from FeSe phonons in a monolayer

Abstract

We show that electron–phonon coupling can induce strong electron pairing in an FeSe monolayer on a SrTiO _3 substrate (experimental indications for superconducting ${T}_{{\rm{c}}}$ are between 65 and 109 K). The role of the SrTiO _3 substrate in increasing the coupling is two-fold. First, the interaction of the FeSe and TiO _2 terminated face of SrTiO _3 prevents the FeSe monolayer from undergoing a shear-type (orthorhombic, nematic) structural phase transition. Second, the substrate allows an anti-ferromagnetic ground state of FeSe which opens electron–phonon coupling channels within the monolayer that are prevented by symmetry in the non-magnetic phase. The spectral function for the electron–phonon coupling ( ${\alpha }^{2}F$ ) in our calculations agrees well with inelastic tunneling data.

Keywords

• superconductivity
• FeSe
• phonons structure
• nematic
• monolayer
• SrTiO3