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

TL;DR

This study investigates the atomic-scale interactions at the MgB₂/SiC interface, revealing how interface-induced phonon softening enhances electron-phonon coupling, which could improve superconducting properties.

Contribution

It provides atomic-level insights into phonon softening and electron-phonon coupling enhancement at the MgB₂/SiC interface through combined experimental and theoretical analysis.

Findings

Detection of MgO layer at the interface

Observation of phonon mode splitting and softening

Confirmation of enhanced electron-phonon coupling via calculations

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.