Gate-tunable hallmarks of unconventional superconductivity in non-centrosymmetric nanowires

Abstract

Two dimensional SrTiO3-based interfaces stand out among non-centrosymmetric superconductors due to their intricate interplay of gate tunable Rashba spin-orbit coupling and multi-orbital electronic occupations, whose combination theoretically prefigures various forms of non-standard superconductivity. However, a convincing demonstration by phase sensitive measurements has been elusive so far. Here, by employing superconducting transport measurements in nano-devices we present clear-cut experimental evidences of unconventional superconductivity in the LaAlO3/SrTiO3 interface. The central observations are the substantial anomalous enhancement of the critical current by small magnetic fields applied perpendicularly to the plane of electron motion, and the asymmetric response with respect to the magnetic field direction. These features have a unique trend in intensity and sign upon electrostatic gating that, together with their dependence on temperature and nanowire dimensions, cannot be accommodated within a scenario of canonical spin-singlet superconductivity. We theoretically demonstrate that the hall-marks of the experimental observations unambiguously indicate a coexistence of Josephson channels with sign difference and intrinsic phase shift. The character of these findings establishes the occurrence of independent components of unconventional pairing in the superconducting state due to inversion symmetry breaking. The outcomes open new venues for the investigation of multi-orbital non-centrosymmetric superconductivity and Josephson-based devices for quantum technologies.

arXiv comment9 pages, 4 figures

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• Anomalous Josephson Coupling and High-Harmonics in Non-Centrosymmetric Superconductors with $S$-wave Spin-Triplet Pairing
• Probing Topological Superconductivity of oxide nanojunctions using fractional Shapiro steps
• Frustration driven Josephson phase dynamics
• Supercurrent Diode Effect in Josephson Interferometers with Multiband Superconductors
• Interplay between the extended s-wave symmetry of the gap and the spin-orbit coupling in the low-electron concentration regime of quasi-two-dimensional superconductors
• Coexistence of high electron-mobility, unpaired spins, and superconductivity at high carrier density SrTiO${}_3$-based interfaces
• Particle-hole spectral asymmetry at the edge of multiorbital noncentrosymmetric superconductors