Atomic-Scale Mechanism of Enhanced Electron-Phonon Coupling at the Interface of MgB<sub>2</sub> Thin Films.
basic_science · Level V
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- Record sourced from PubMed, PMID 39378194.
- Also identified by DOI 10.1021/acs.nanolett.4c03170.
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Abstract
In conventional Bardeen-Cooper-Schrieffer (BCS) superconductors, electron-phonon coupling is the fundamental mechanism of superconductivity. For instance, the superconductivity of magnesium diboride (MgB<sub>2</sub>) comes from the coupling between <i>E</i><sub><i>2g</i></sub> modes (in-plane boron-boron bond vibrations) and self-doped charge carriers. In thin films and ceramics of BCS superconductors, interfaces with discontinuous chemical bonds may alter the local electron-phonon coupling. However, such effects remain largely unexplored. Here, we investigate the heterointerface of the MgB<sub>2</sub> film on the SiC substrate at the atomic scale using electron microscopy and spectroscopy. We detect the presence of a thin MgO layer with a thickness of ∼1 nm between MgB<sub>2</sub> and SiC. Atomic-level electron energy loss spectra (EELS) show MgB<sub>2</sub>-<i>E</i><sub><i>2g</i></sub> mode splitting and softening near the MgB<sub>2</sub>/MgO interface, which enhances electron-phonon coupling at the interface. Our findings highlight the potential of interface engineering to enhance superconductivity via modulating local phonon states and/or electron states.