interfaces by monochromted STEM-EELS*

Monolayer FeSe films grown on SrTiO₃ substrate show over ten-fold increase in superconducting Tc compared to bulk FeSe. The interfacial electron-phonon coupling has been thought as one key factor for the Tc enhancement. So far, the main experimental evidence for electron-phonon coupling is the ~100 meV replica bands observed in angle resolved photoemission spectroscopy. In order to provide an atomic scale understanding of the electron-phonon interaction, here we study the phonons at FeSe/SrTiO₃ interface by Å-sized electron beam. We study FeSe/SrTiO₃ samples by high resolution electron energy loss spectroscopy in a monochromated scanning transmission electron microscope. We will present atomically resolved phonon spectral images of the FeSe/SrTiO₃ interface. Together with the interface atomic structure and chemistry, we will also discuss possible origin of the phonon modes with strong EPC.