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

Abstract

The magnetization and magnetic torque of a high-quality single crystal of Sr2RuO4 have been measured down to 0.1 K under 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±0.15) G at the upper critical field Hc2,ab∼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 Γ=ξa/ξc of as large as 60 even at 100 mK, in contrast with the observed Hc2 anisotropy of ∼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 Sr2RuO4.

Source-reported materials — not catalogue approval

Similar papers