Giant spin polarization and a pair of antiparallel spins in a chiral superconductor

Chiral molecules can exhibit spin-selective charge emission, which is known as chirality-induced spin selectivity(1,2). Despite the constituent light elements of the molecules, their spin polarization can approach or even exceed that of typical ferromagnets. This powerful capability may lead to applications in the chiral spintronics(2) field. Although the origin of spin selectivity is elusive, two microscopic phenomena have been suggested based on experimental results: effective enhancement of spin-orbit interactions(3) and chirality represented by a pair of oppositely polarized spins(4,5). However, the hypotheses remain to be verified. Here we report the simultaneous observation of these two phenomena in an organic chiral superconductor by magnetoresistance measurements in the vicinity of the superconducting transition temperature. A pair of oppositely polarized spins is demonstrated by spatially mapping the spin polarity in an electric alternating current excitation. The obtained spin polarization exceeds that of the Edelstein effect(6-10) by several orders of magnitude, which indicates an effective enhancement of the spin-orbit interaction. Our results demonstrate a solid-state analogue of spin accumulations assumed for chiral molecules, and may provide clues to the origin of their molecular counterparts. In addition, the innovative capability of spin-current sourcing will invigorate superconducting spintronics research(11).

Automated summary

Chiral molecules exhibit spin-selective charge emission, which is called chirality-induced spin selectivity. Despite being made of light elements, their spin polarization can exceed that of typical ferromagnets. This has potential applications in the chiral spintronics field. Through magnetoresistance measurements, we observed the two suggested phenomena, effective enhancement of spin-orbit interactions and chirality represented by oppositely polarized spins, in an organic chiral superconductor. Our findings provide insights into the origin of spin selectivity in chiral molecules and contribute to the development of superconducting spintronics research.