Effects of superconducting gap anisotropy on the flux flow resistivity   in Y(Ni_{1-x}Pt_x)_2B_2C
  The microwave complex surface impedance Z_s of Y(Ni_{1-x}Pt_x)_2B_2C was measured at 0.5 K under magnetic fields H up to 7T. In nominally pure YNi_2B_2C, which is a strongly anisotropic s-wave superconductor, the flux flow resistivity \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 \rho_f is reduced and \rho_f approaches to the conventional behavior. These results indicate that energy dissipation in the vortex core is strongly affected by the anisotropy of the superconducting gap. 
K. Takaki, A. Koizumi, T. Hanaguri, M. Nohara, H. Takagi, K. Kitazawa,   Y. Kato, Y. Tsuchiya, H. Kitano and A. Maeda