Electron-Polarization Coupling in Superconductor-Ferroelectric Superlattices

TL;DR

This paper develops a phenomenological model for ferroelectric-superconductor heterostructures, revealing how interface coupling influences phase stability, polarization, and superconductivity, with implications for high-temperature superconductor films on ferroelectric substrates.

Contribution

It introduces a new model describing interface coupling effects in FE-S superlattices, predicting phase coexistence and topology changes in phase diagrams based on layer thicknesses.

Findings

Stable domain-type phase with contact-induced polarization.

Coexistence of ferroelectric and suppressed superconducting phases.

Phase diagram topology varies with layer thickness.

Abstract

We present a phenomenological model of periodic ferroelectric-superconductor (FE-S) heterostructures containing two alternating ferroelectric and superconducting layers. The interaction at the FE-S contacts is described as a coupling of the local carrier density of the superconductor with the spontaneous ferroelectric polarization near the FE-S interface. We obtain a stable symmetric domain-type phase exhibiting a contact-induced polarization and the ferroelectric domain structure at temperatures above the bulk ferroelectric transition temperature. With an increasing coupling energy, we find the appearance of the ferroelectric phase coexisting with the suppressed superconductivity in the S-film. The system is analyzed for different thicknesses of the FE- and S-films demonstrating the dramatic change of the topology of the phase diagrams with a variation of the layers thickness. The results are expected to shed light on the processes occurring in high-temperature superconducting films grown on perovskite alloy-substrates exhibiting ferroelectric properties at lower temperatures.