Enhanced Superconductivity at Quantum-Critical KTaO3 Interfaces

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.