Unconventional Superconductivity and Spin-Active Interfaces in Chiral Material/Superconductor Heterostructures

We report on unconventional superconducting phenomena observed in noble metal/superconductor heterostructures with strong spin-orbit coupling [1]. Using epitaxially grown chiral materials as tunnel barriers, we achieve high-resolution spectroscopy revealing distinct bulk and surface superconducting gaps at chiral material/noble metal interfaces. Our measurements demonstrate a significantly enhanced interface Zeeman field, characterized by an effective Landé g-factor of ~12, far exceeding typical values. This localized field selectively suppresses surface superconductivity while preserving the bulk state, violating the Pauli paramagnetic limit. We observe spin-polarized Andreev bound states, corroborating a spin-active interface, and a robust superconducting gap under large magnetic field. The interplay between structural chirality, strong spin-orbit coupling, and superconductivity creates a unique platform for investigating chirality-induced spin selectivity and exotic quantum states. Additionally, we demonstrate the potential of these heterostructures for quantum device applications through high-quality superconducting resonators. Our work opens new avenues for exploring unconventional superconductivity, spintronics, and potentially topological states in this versatile material system.
[1] Chen et al., Sci. Adv. 10, eado4875 (2024)