Dr. Yufan Li, Department of Physics and Astronomy, Johns Hopkins University
When
Abstract: Spin-triplet pairing is a rare occurrence in condensed matter physics, so far only confirmed in 3He superfluid. No solid-state material has been confirmed to manifest spin-triplet pairing. On the other hand, there are surging interest in the spin-triplet p-wave pairing due to its close relevance to topological superconductivity and noise-resilient quantum computing. We show that the magnetic flux quantization, one of the defining characteristics of a superconductor (SC), could serve as a decisive phase-sensitive method to distinguish triplet-pairing SCs from the most common spin-singlet SCs. A superconducting ring with triplet pairing may demonstrate half-integer flux quantization. In other words, half flux quanta with fractional quantum numbers of 1/2, 3/2, 5/2, etc. are energetically favored, instead of integer numbers of 0, 1, 2, etc. We have observed half-quantum flux in mesoscopic rings of superconducting Beta-Bi2Pd thin films [1]. The result provides conclusive evidence for spin-triplet p-wave pairing, expected for Beta-Bi2Pd as a leading candidate material of intrinsic topological SCs. We have also observed half-quantum flux in noncentrosymmetric α-BiPd, where an admixture of singlet and triplet pairing is expected [2]. Our findings usher in new venues for studying topological superconductivity, and new designs of flux qubit for quantum computing, which may operate without external magnetic fields.
[1] Science 366, 238-241 (2019).
[2] Physical Review Letters 124, 167001 (2020)
Zoom Link: https://arizona.zoom.us/j/97743029541 (This event is password protected. Please email the host, Dr. Weigang Wang, to be emailed the password.)