Enhanced superconductivity and coexisting ferroelectricity at oxide interfaces

TL;DR

Researchers found that superconductivity and ferroelectricity can coexist at oxide interfaces, with ferroelectric effects enhancing superconducting properties.

Contribution

The study reveals a new mechanism where ferroelectric polarization enhances superconductivity at oxide interfaces.

Findings

Superconducting transition temperature increases by ~0.2–0.6 K due to ferroelectric polarization.

Bistable transport properties and hysteresis suggest switchable ferroelectric polarization.

Ferroelectricity is robust below 50 K at the LaAlO3/KTaO3 interface.

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 an 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. Raman scattering measurements and 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.

The authors experimentally demonstrate the coexistence of superconductivity and ferroelectricity at LaAlO3/KTaO3 interfaces. The superconducting transition temperature is enhanced due to ferroelectric polarization-induced reduction in dielectric constant, which narrows the interfacial potential well, confining carriers closer to the interface.

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