Effect of strong surface pinning on the surface impedance of a superconductor in a mixed state

The field and frequency dependences of the surface impedance of a type-II s uperconductor in a mixed state in a constant magnetic field perpendicular t o the surface are calculated taking account of the nonlocality of the elast ic moduli of the vortex lattice. It is shown that if there is no surface pi nning, a correct analysis of the elastic properties of the vortex ensemble results in the Coffey-Clem model with small corrections. For strong surface pinning, the surface resistance is predicted to decrease substantially at low frequencies. It is shown that the results obtained when dispersion is t aken into account by renormalizing the elastic moduli [E. B. Sonin, A. K. T agantsev, and K. B. Traito, Phys. Rev. B 46, 5830 (1992)] are incorrect. (C ) 2001 American Institute of Physics.