Universally enhanced superconductivity and coexisting ferroelectricity at oxide interfaces

TL;DR

This study demonstrates the coexistence and mutual enhancement of superconductivity and ferroelectricity at LaAlO3/KTaO3 interfaces, revealing a universal Tc increase and switchable ferroelectric polarization effects.

Contribution

It uncovers a novel mechanism linking ferroelectricity and superconductivity at oxide interfaces, with experimental evidence of their coexistence and mutual influence.

Findings

Superconductivity and ferroelectricity coexist at LaAlO3/KTaO3 interfaces.

Ferroelectric polarization enhances the superconducting transition temperature.

Switchable ferroelectric polarization modulates interfacial carrier confinement.

Abstract

The coexistence of superconductivity and ferroelectricity is rare due to their conflicting requirements: superconductivity relies on free charge carriers, whereas ferroelectricity typically occurs in insulating systems. At LaAlO3/KTaO3 interfaces, we demonstrate the coexistence of two-dimensional superconductivity and ferroelectricity, enabled by the unique properties of KTaO3 as a quantum paraelectric. Systematic gating and poling experiments reveal a universal enhancement of the superconducting transition temperature (Tc) by 0.2-0.6 K and bistable transport properties, including hysteresis, strongly suggesting the existence of switchable ferroelectric polarization in the interfacial conducting layer. Hysteresis loops indicate robust ferroelectricity below 50 K. The Tc enhancement is attributed to ferroelectric polarization-induced reduction in dielectric constant, which narrows the interfacial potential well, confining carriers closer to the interface. The bistability arises from switchable ferroelectric polarization, which modulates the potential well depending on polarization direction. These findings establish a straightforward mechanism coupling ferroelectricity and superconductivity, providing a promising platform for exploring their interplay.