arXiv subjects

Daisuke Shibata

Publications and source records attributed to Daisuke Shibata.

2 recordsLinked to original sources

arXiv2015

Quenched metastable vortex states in Sr2RuO4

Sr2RuO4, a leading-candidate spin-triplet superconductor and a highly anisotropic quasi-two-dimensional type-II superconductor, provides unique opportunity to study unconventional as well as conventional vortex phases. To investigate its vortex-matter phases, we studied the ac susceptibility of Sr2RuO4 for fields parallel to the RuO2 plane by adapting two different thermal processes: In addition to the ordinary field sweep (FS) process, we newly employed the "each-point field cooling (EPFC)" process, in which the superconductivity is once thermally destroyed before collecting the data. We find that the ac susceptibility signal substantially changes with the EPFC process.This result indicates that we succeed in inducing new metastable vortex states by the EPFC process.We also find a new field scale H*1, below which the FS and EPFC processes provide the same value of the ac susceptibility. This new field scale suggests a liquid-like vortex state in the low-field region.

cond-mat.supr-con↗

arXiv2014

Sharp magnetization jump at the first-order superconducting transition in Sr2RuO4

The magnetization and magnetic torque of a high-quality single crystal of Sr$_2$RuO$_4$ have been measured down to 0.1 K under a precise control of the magnetic-field orientation. When the magnetic field is applied exactly parallel to the $ab$ plane, a sharp magnetization jump $4πδM$ of $(0.74 \pm 0.15)$ G at the upper critical field $H_{{\rm c2},{ab}} \sim 15$ kOe with a field hysteresis of 100 Oe is observed at low temperatures, evidencing a first-order superconducting-normal transition. A strong magnetic torque appearing when $H$ is slightly tilted away from the $ab$ plane confirms an intrinsic anisotropy $\varGamma=ξ_a/ξ_c$ of as large as 60 even at 100 mK, in contrast with the observed $H_{\rm c2}$ anisotropy of $\sim 20$. The present results raise fundamental issues in both the existing spin-triplet and spin-singlet scenarios, providing, in turn, crucial hints toward the resolution of the superconducting nature of Sr$_2$RuO$_4$.

cond-mat.supr-con↗