Magnetoresistance oscillation study of the half-quantum vortex in doubly connected mesoscopic superconducting cylinders of Sr2RuO4

Abstract

The observation of the highly unusual half-quantum vortex (HQV) in a single crystalline superconductor excludes unequivocally the spin-singlet symmetry of the superconducting order parameter. HQVs were observed previously in mesoscopic samples of Sr2RuO4 in cantilever torque magnetometry measurements, thus providing direct evidence for spin-triplet pairing in the material. In addition, it raised important questions on HQV, including its stability and dynamics. These issues have remained largely unexplored, in particular, experimentally. We report in this paper the detection of HQVs in mesoscopic, doubly connected cylinders of single-crystalline Sr2RuO4 of a mesoscopic size and the examination of the effect of the in-plane magnetic field needed for the observation of the HQV by magnetoresistance (MR) oscillations measurements. Several distinct features found in our data, especially a dip and secondary peaks in the MR oscillations seen only in the presence of a sufficiently large in-plane magnetic field as well as a large measurement current, are linked to the formation of the HQV fluxoid state in and crossing of an Abrikosov HQV through the sample. The conclusion is drawn from the analysis of our data using a model of thermally activated vortex crossing overcoming a free-energy barrier which is modulated by the applied magnetic flux enclosed in the cylinder as well as the measurement current. Evidence for the trapping of an HQV fluxoid state in the sample was also found. Our observation of the HQV in mesoscopic Sr2RuO4 provided not only additional evidence for spin-triplet superconductivity in Sr2RuO4 but also insights into the physics of HQV, including its spontaneous spin polarization, stability, and dynamics. Our study also revealed a possible effect of the measurement current on the magnitude of the spontaneous spin polarization associated with the HQV.

17 pages and 7 figures

References in corpus (6)

• High Resolution Polar Kerr Effect Measurements of Sr2RuO4: Evidence for Broken Time Reversal Symmetry in the Superconducting State
• Chiral P-Wave Order in Sr_2RuO_4
• Observation of half-height magnetization steps in Sr2RuO4
• Half quantum vortex in superfluid ${}^3$He-A phase in parallel plate geometry
• Little-Parks oscillations with half-quantum fluxoid features in Sr2RuO4 micro rings
• Effect of half-quantum vortices on magnetoresistance of perforated superconducting films

Cited by in corpus (4)

• Strain-induced time reversal breaking and half quantum vortices near a putative superconducting tetra-critical point in Sr${}_2$RuO${}_4$
• A microscopic Ginzburg--Landau theory and singlet ordering in Sr${}_2$RuO${}_4$
• Berezinskii-Kosterlitz-Thouless transition transport in spin-triplet superconductor
• Little-Parks oscillation and $\mathbf{d}$-vector texture in spin-triplet superconducting rings with bias current