Correlation of Fe-based Superconductivity and Electron-Phonon Coupling in an FeAs/Oxide Heterostructure

TL;DR

This study investigates how interfacial phonons influence superconductivity in an FeAs/oxide heterostructure, providing real-space evidence of electron-phonon interactions enhancing pairing in iron-based superconductors.

Contribution

It offers the first real-space evidence linking interfacial phonons and electron-phonon coupling to superconductivity in Fe-based heterostructures, supported by experimental and theoretical analysis.

Findings

Interfacial phonons modulate superconducting gaps via e-ph interaction.

Self-consistent Eliashberg calculations support phonon-mediated pairing.

Local variations in superconductivity correlate with interfacial phonon activity.

Abstract

Interfacial phonons between iron-based superconductors (FeSCs) and perovskite substrates have received considerable attention due to the possibility of enhancing preexisting superconductivity. Using scanning tunneling spectroscopy, we studied the correlation between superconductivity and e-ph interaction with interfacial-phonons in an iron-based superconductor Sr$_2$VO$_3$FeAs ($T_c \approx$ 33 K) made of alternating FeSC and oxide layers. The quasiparticle interference measurement over regions with systematically different average superconducting gaps due to the e-ph coupling locally modulated by O vacancies in VO$_2$ layer, and supporting self-consistent momentum-dependent Eliashberg calculations provide a unique real-space evidence of the forward-scattering interfacial phonon contribution to the total superconducting pairing.