Little-Parks oscillations with half-quantum fluxoid features in Sr2RuO4 micro rings

Abstract

In a micro ring of a superconductor with a spin-triplet equal-spin pairing state, a fluxoid, a combined object of magnetic flux and circulating supercurrent, can penetrate as half-integer multiples of the flux quantum. A candidate material to investigate such half-quantum fluxoids is Sr${}_2$RuO${}_4$. We fabricated Sr${}_2$RuO${}_4$ micro rings using single crystals and measured their resistance behavior under magnetic fields controlled with a three-axes vector magnet. Proper Little-Parks oscillations in the magnetovoltage as a function of an axially applied field, associated with fluxoid quantization are clearly observed, for the first time using bulk single crystalline superconductors. We then performed magnetovoltage measurements with additional in-plane magnetic fields. By carefully analyzing both the voltages $V_{+}$ ($V_{-}$) measured at positive (negative) current, we find that, above an in-plane threshold field of about 10 mT, the magnetovoltage maxima convert to minima. We interpret this behavior as the peak splitting expected for the half-quantum fluxoid states.

16 pages, 15 figures

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• Absence of ${}^{17}$O Knight-Shift Changes across the First-Order Phase Transition Line in Sr${}_2$RuO${}_4$

Cited by in corpus (3)

• Identifying possible pairing states in Sr${}_2$RuO${}_4$ by tunneling spectroscopy
• Theoretical studies for identifying horizontal line nodes via angle-resolved density of states measurements ---Application to Sr${}_2$RuO${}_4$---
• Half-quantum vortices on c-axis domain walls in chiral p-wave superconductors