Temperature and Frequency Dependence of the Surface Resistance in the Vortex State of Type-II Superconductors

The temperature and frequency dependence of surface-resistance data obtained in the vortex state of superconducting Pb-In alloys are analyzed. Measurements near $H_{c2\mathrm{}}$ indicate the normalized slope $s\frac{1}{2}=\left(\frac{H_{c2\mathrm{}}}{R_n}\right)\frac{\partial R}{\partial H}{|}_{H_{c2\mathrm{}}}$ tends to go to zero as the critical temperature is approached. The data are accounted for qualitatively if the frequency dependence of the fluxflow conductivity (dynamical fluctuations) is retained in the expression for the microwave current. There is no exact quantitative agreement, and the possibility of a strong-coupling correction is suggested.