Spontaneous rotational symmetry breaking in KTaO${}_3$ heterointerface superconductors

Abstract

Broken symmetries play a fundamental role in superconductivity and influence many of its properties in a profound way. Understanding these symmetry breaking states is essential to elucidate the various exotic quantum behaviors in non-trivial superconductors. Here, we report an experimental observation of spontaneous rotational symmetry breaking of superconductivity at the heterointerface of amorphous (a)-YAlO${}_3$/KTaO${}_3$(111) with a superconducting transition temperature of 1.86 K. Both the magnetoresistance and superconducting critical field in an in-plane field manifest striking twofold symmetric oscillations deep inside the superconducting state, whereas the anisotropy vanishes in the normal state, demonstrating that it is an intrinsic property of the superconducting phase. We attribute this behavior to the mixed-parity superconducting state, which is an admixture of \emph{s}-wave and \emph{p}-wave pairing components induced by strong spin-orbit coupling inherent to inversion symmetry breaking at the heterointerface of a-YAlO${}_3$/KTaO${}_3$. Our work suggests an unconventional nature of the underlying pairing interaction in the KTaO${}_3$ heterointerface superconductors, and brings a new broad of perspective on understanding non-trivial superconducting properties at the artificial heterointerfaces.

arXiv comment9 pages, 4 figures

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• Coexistence of ferromagnetism and superconductivity at KTaO${}_3$ heterointerfaces
• Violation of Pauli Limit at KTaO3(110) Interfaces
• Unique quantum metallic state in the titanium sesquioxide heterointerface superconductor
• Ubiquity of rotational symmetry breaking in superconducting films, from Fe(Te,Se)/Bi${}_2$Te${}_3$ to Nb, and the effect of measurement geometry
• Field misalignment effect on the in-plane magnetoresistance in the high-temperature superconductor FeSe/SrTiO3
• Geometric Control of Pairing: Universal Scaling of Superconductivity at KTaO3 Interfaces
• Percolative Pathway to Stripe Order in KTaO3-Based Superconductivity
• Observation of Quantum-Criticality-Class Crossover at the LaAlO${}_3$/KTaO${}_3$ (111) Interface