Electron-phonon coupling enhanced by the FeSe/SrTiO_3 interface

摘要

The electronic structure, phonon dispersions, and electron-phonon (EP) coupling in Fe_2Se_2/SrTiO_3 (FeSe/STO) thinnest films are studied based on the first-principles calculations. It is found that the FeSe/STO interface with lattice strain leads to a change of band structures and a significant enhancement of the EP coupling, the latter being close related to interface-induced ferroelectric phonons coupled to electrons on the FeSe monolayer. In the FeSe/STO system, T_c of phonon-induced superconductivity is estimated to be much greater than that in the bulk FeSe, but still well below the experimental value of an FeSe monolayer on the STO substrate, indicating that the electron-phonon mechanism alone cannot explain its high T_c.