Effects of superconducting gap anisotropy on the flux flow resistivity inY(Ni1−xPtx)2B2C

Abstract

The microwave complex surface impedance ${Z}_{s}$ of $\mathrm{Y}({\mathrm{Ni}}_{1\ensuremath{-}x}{\mathrm{Pt}}_{x}{)}_{2}{\mathrm{B}}_{2}\mathrm{C}$ was measured at 0.5 K under magnetic fields H up to 7 T. In nominally pure ${\mathrm{YNi}}_{2}{\mathrm{B}}_{2}\mathrm{C},$ which is a strongly anisotropic s-wave superconductor, the flux flow resistivity ${\ensuremath{\rho}}_{f}$ calculated from ${Z}_{s}$ was twice as large as that expected from the conventional normal-state vortex core model. In Pt-doped samples where the gap anisotropy is smeared out, the enhancement of ${\ensuremath{\rho}}_{f}$ is reduced and ${\ensuremath{\rho}}_{f}$ approaches the conventional behavior. These results indicate that the energy dissipation in the vortex core is strongly affected by the anisotropy of the superconducting gap.