Potentiometric detection of spin polarization expected at the surface of FeTe₀.₆Se₀.₄ in the effective 𝑝-wave superconducting state

The quest for non-Abelian anyons is attracting tremendous attention. A Majorana quasiparticle has attracted great interest since the non-Abelian anyon is a key particle for topological quantum computation. Much effort has been made toward the quest of the Majorana state in solids, and some candidate material platforms have been reported. Among various materials that can host the Majorana state, a chiral 𝑝-wave superconductor is one of the suitable materials, and the iron-based layered superconductor FeTeSe is one of the promising material platforms because its surface can host an effective 𝑝-wave superconducting state that is analogous to the chiral 𝑝-wave superconducting state thanks to its topological surface state. Given that a chiral 𝑝-wave superconductor possesses spin polarization, detecting the spin polarization can be evidence for the chiral 𝑝-wave trait, which results in the existence of Majorana excitation. Here, we show successful detection of the spin polarization at the surface of FeTe₀.₆⁢Se₀.₄ in its superconducting state, where the spin polarization is detected via a potentiometric method. Amplitudes of the spin signal exhibit characteristic dependence for temperature and bias current, suggesting detection of spin polarization of the Bogoliubov quasiparticles. Our achievement opens an avenue to exploration of topological superconductivity for fault-tolerant quantum computation.