Atomic-scale mechanism of enhanced electron-phonon coupling at the interface of MgB${}_2$ thin film

Abstract

In this study, we explore the heterointerface of MgB${}_2$ film on SiC substrate at atomic scale using electron microscopy and spectroscopy. We detect ~1 nm MgO between MgB${}_2$ and SiC. Atomic-level electron energy loss spectra (EELS) show MgB${}_2$-E2g mode splitting and softening near the MgB${}_2$/MgO interface. Orbital-resolved core-level EELS link the phonon softening to in-plane boron-atom electron states' changes. Ab initio calculations confirm this softening enhances electron-phonon coupling at the interface. Our findings highlight interface engineering's potential for superconductivity enhancement.