Monolayer films of FeSe grown on ${\mathrm{SrTiO}}_3$ substrates exhibit significantly higher superconducting transition temperatures than those of bulk FeSe. Interaction of electrons in the FeSe layer with dipolar ${\mathrm{SrTiO}}_3$ phonons has been suggested as the cause of the enhanced transition temperature. In this paper we systematically study the coupling of ${\mathrm{SrTiO}}_3$ longitudinal-optical phonons to the FeSe electron, including also electron-electron Coulomb interactions at the random phase approximation level. We find that the electron-phonon interaction between FeSe and ${\mathrm{SrTiO}}_3$ substrate is almost entirely screened by the electronic fluctuations in the FeSe monolayer, so that the net electron-phonon interaction is very weak and unlikely to lead to superconductivity.

• Received 21 March 2017
• Revised 16 June 2017

DOI:https://doi.org/10.1103/PhysRevB.96.054516