Observation of Half-Quantum Flux in Unconventional Superconductor $\beta$-Bi$_2$Pd

TL;DR

This study reports the detection of half-integer magnetic flux quantization in mesoscopic rings of $eta$-Bi$_2$Pd, providing evidence for its unconventional, possibly spin-triplet, topological superconductivity.

Contribution

The paper presents the first observation of half-quantum fluxoids in $eta$-Bi$_2$Pd, supporting its classification as an unconventional topological superconductor.

Findings

Half-integer flux quantization observed in $eta$-Bi$_2$Pd rings

Evidence of $eta$-Bi$_2$Pd being a topological superconductor

Strong indication of spin-triplet pairing

Abstract

We report the observation of half-integer magnetic flux quantization in mesoscopic rings of superconducting $\beta$-Bi$_2$Pd thin films. The half-quantum fluxoid manifests itself as a $\pi$ phase shift in the quantum oscillation of the critical temperature. This result verifies unconventional superconductivity of $\beta$-Bi$_2$Pd, in accord with the expectation of a topological superconductor. We also discuss the strong indication that $\beta$-Bi$_2$Pd is a spin-triplet superconductor.