Observation of plasmon-phonons in a metamaterial superconductor using inelastic neutron scattering

TL;DR

This paper reports the first experimental observation of plasmon-phonons in Al-Al2O3 metamaterials using inelastic neutron scattering, supporting a new mechanism for enhanced superconductivity.

Contribution

It provides experimental evidence for hybrid plasmon-phonon excitations as a mechanism for increased Tc in metamaterial superconductors, validating a theoretical model.

Findings

Observation of hybrid plasmon-phonon excitations in metamaterials

Support for a new superconductivity mechanism involving plasmon-phonons

Explanation of Tc enhancement in granular aluminium films

Abstract

Metamaterial approach is capable of drastically increasing the critical temperature, Tc, of composite metal-dielectric superconductors. Tripling of Tc was observed in bulk Al-Al2O3 core-shell metamaterials. A theoretical model based on the Maxwell-Garnett approximation provides a microscopic explanation of this effect in terms of electron-electron pairing mediated by a hybrid plasmon-phonon excitation. We report the first observation of this excitation in Al-Al2O3 core-shell metamaterials using inelastic neutron scattering. This result provides support for this novel mechanism of superconductivity in metamaterials and explains the 50 year old mystery of enhanced Tc in granular aluminium films.