Dynamic interfacial polaron enhanced superconductivity of FeSe/SrTiO3

TL;DR

This paper investigates how dynamic interfacial polarons formed by electron-lattice interactions at the FeSe/SrTiO3 interface enhance superconductivity, combining spectroscopy experiments and a microscopic model.

Contribution

It provides experimental evidence of interfacial polarons and develops a microscopic model linking polaron interactions to superconductivity enhancement.

Findings

Electrons are dressed by polarized lattice distortions of SrTiO3.

Formation of dynamic interfacial polarons due to non-adiabatic coupling.

Polaronic plasmons are correlated with surface phonons and linked to superconductivity.

Abstract

The observation of substantially enhanced superconductivity of single-layer FeSe films on SrTiO3 has stimulated intensive research interest. At present, conclusive experimental data on the corresponding electron-boson interaction is still missing. Here we use inelastic electron scattering spectroscopy and angle resolved photoemission spectroscopy to show that the electrons in these systems are dressed by the strongly polarized lattice distortions of the SrTiO3, and the indispensable non-adiabatic nature of such a coupling leads to the formation of dynamic interfacial polarons. Furthermore, the collective motion of the polarons results in a polaronic plasmon mode, which is unambiguously correlated with the surface phonons of SrTiO3 in the presence of the FeSe films. A microscopic model is developed showing that the interfacial polaron-polaron interaction leads to the superconductivity enhancement.