Unequivocal Determination of Spin-Triplet Superconductivity Using Composite Rings

TL;DR

This study uses phase-sensitive measurements on composite superconducting rings to definitively identify the odd-parity spin-triplet pairing symmetry of $eta$-Bi$_2$Pd, a superconductor with potential topological properties.

Contribution

The paper demonstrates a novel phase-sensitive approach with composite rings to conclusively determine the spin-triplet pairing symmetry of $eta$-Bi$_2$Pd.

Findings

Observation of half-integer quantum flux indicating odd-parity pairing

Confirmation of triplet superconductivity in $eta$-Bi$_2$Pd

Use of epitaxial $eta$-Bi$_2$Pd and Nb in composite rings

Abstract

Phase-sensitive measurements on a composite ring made of a superconductor of interest connected by a known singlet $s$-wave superconductor can unambiguously determine its pairing symmetry. In composite rings with epitaxial $\beta-$Bi$_2$Pd and $s$-wave Nb, we have observed half-integer quantum flux when Nb is connected to the opposite crystalline ends of $\beta-$Bi$_2$Pd and integer-quantum flux when Nb is connected to the same crystalline ends of $\beta-$Bi$_2$Pd. These findings provide unequivocal evidence of odd-parity pairing state of the triplet superconductor $\beta-$Bi$_2$Pd.