Verification of Anisotropic s-Wave Superconducting Gap Structure in CeRu

概要

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The field-angle-resolved specific heat C(T,H,\phi) of the f-electron superconductor CeRu<inf>2</inf>(T_{\text{c}}=6.3 K) has been measured at low temperatures down to 90 mK on two single crystals of slightly different qualities. We reveal that the C(\phi) oscillation in a rotating magnetic field, originating from the gap anisotropy, diminishes at low temperatures below the characteristic field H^{\ast}, as expected for an anisotropic gap without nodes. We also observe the suppression of H^{\ast} by decreasing the gap anisotropy ratio \Delta_{\text{min}}/\Delta_{\text{max}}, a behavior that has been predicted from a microscopic theory for anisotropic s-wave superconductors. The present technique is established as a powerful tool for investigating minimum-gap structures as well as nodal structures.
2013-12-15