Large electron-phonon interactions from FeSe phonons in a monolayer

TL;DR

This paper demonstrates that strong electron-phonon interactions in a monolayer FeSe on SrTiO3 substrate can induce high-temperature superconductivity, with substrate effects enhancing coupling and preventing structural transitions.

Contribution

It reveals how the SrTiO3 substrate enhances electron-phonon coupling and stabilizes magnetic states, leading to potential high-temperature superconductivity in FeSe monolayers.

Findings

Electron-phonon coupling can induce superconductivity in FeSe monolayers.

The substrate prevents structural phase transitions and enables magnetic states.

Calculated spectral functions match experimental tunneling data.

Abstract

We show that electron-phonon coupling can induce strong electron pairing in an FeSe monolayer on a SrTiO3 substrate (experimental indications for superconducting Tc are between 65 and 109K). The role of the SrTiO3 substrate in increasing the coupling is two-fold. First, the interaction of the FeSe and TiO2 terminated face of SrTiO3 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 (alpha2F) in our calculations agrees well with inelastic tunneling data.