Unconventional quantum oscillations in mesoscopic rings of spin-triplet superconductor Sr2RuO4

TL;DR

This study investigates quantum oscillations in mesoscopic Sr2RuO4 rings, revealing vortex-related effects and unconventional oscillation periods, but no half-flux-quantum oscillations without in-plane magnetic fields.

Contribution

It demonstrates the presence of vortex-induced quantum oscillations in Sr2RuO4 rings and distinguishes their behavior from conventional effects, highlighting vortex lattice lock-in phenomena.

Findings

Observed quantum oscillations with full-flux quantum period

Detected different oscillation periods in thick-wall rings at varying fields

Found no evidence of half-flux-quantum oscillations without in-plane field

Abstract

Odd-parity, spin-triplet superconductor Sr2RuO4 has been found to feature exotic vortex physics including half-flux quanta trapped in a doubly connected sample and the formation of vortex lattices at low fields. The consequences of these vortex states on the low-temperature magnetoresistive behavior of mesoscopic samples of Sr2RuO4 were investigated in this work using ring device fabricated on mechanically exfoliated single crystals of Sr2RuO4 by photolithography and focused ion beam. With the magnetic field applied perpendicular to the in-plane direction, thin-wall rings of Sr2RuO4 were found to exhibit pronounced quantum oscillations with a conventional period of the full-flux quantum even though the unexpectedly large amplitude and the number of oscillations suggest the observation of vortex-flow-dominated magnetoresistance oscillations rather than a conventional Little-Parks effect. For rings with a thick wall, two distinct periods of quantum oscillations were found in high and low field regimes, respectively, which we argue to be associated with the "lock-in" of a vortex lattice in these thick-wall rings. No evidence for half-flux-quantum resistance oscillations were identified in any sample measured so far without the presence of an in-plane field.