Enhanced Superconductivity at Quantum-Critical KTaO3 Interfaces

TL;DR

This study shows that tuning KTaO3 to a ferroelectric quantum critical point significantly boosts interfacial superconductivity, revealing the role of soft phonons in pairing mechanisms and offering new pathways to enhance superconducting properties.

Contribution

The paper demonstrates that proximity to a ferroelectric quantum critical point enhances superconductivity at KTaO3 interfaces, highlighting the importance of quantum criticality and soft phonons in pairing.

Findings

Superconducting transition temperature nearly doubled to 2.9 K at quantum critical doping.

A dome-shaped carrier density dependence appears exclusively at the quantum critical point.

Evidence supports soft-phonon-mediated pairing as a key mechanism.

Abstract

Superconductivity at oxide interfaces has intrigued researchers for decades, yet the underlying pairing mechanism remains elusive. Here we demonstrate that proximity to a ferroelectric quantum critical point dramatically enhances interfacial superconductivity in KTaO3. By precisely tuning KTaO3 to its quantum critical composition through 0.8% niobium doping, we achieve a near-doubling of the superconducting transition temperature, reaching 2.9 K. Remarkably, a dome-shaped carrier density dependence emerges exclusively at the quantum critical point, contrasting sharply with the linear scaling observed in undoped interfaces. Our findings establish ferroelectric quantum criticality as a powerful mechanism for enhancing superconductivity and provide compelling evidence for soft-phonon-mediated pairing in these systems.