Enhanced superconductivity due to forward scattering in FeSe thin films on SrTiO3 substrates

Abstract

Westudy the consequences of an electron-phonon (e-ph) interaction that is strongly peaked in the forward scattering (q = 0) direction in a two-dimensional superconductor usingMigdal-Eliashberg theory. We find that strong forward scattering results in an enhanced Tc that is linearly proportional to the strength of the dimensionless e-ph coupling constant λm in the weak coupling limit. This interaction also produces distinct replica bands in the single-particle spectral function, similar to those observed in recent angle-resolved photoemission experiments on FeSe monolayers on SrTiO3 and BaTiO3 substrates. By comparing our model to photoemission experiments, we infer an e-ph coupling strength that can provide a significant portion of the observed high Tc in these systems.