Upper Critical Field of Granular SnGe Samples Near the Superconductor-to-Insulator Transition

P. J. Lin；S. Y. Hsu

Chinese Journal of Physics

43卷3S期（2005 / 06 / 01）

662 - 665

英文

We have measured the upper critical field, Hc2(T ), in granular SnGe samples with normal state resistivities, ρN, that range from 0.3 mΩ cm to 0.5 Ω cm. The samples demonstrate an evolution from superconducting to insulating in transport with increasing disorder. The temperature dependence of Hc2 shows a clear change in curvature between high ρN and intermediate ρN samples differing from the experimental results by Deutscher et al.. Our data is analyzed in terms of Ginzburg-Landau theory and grain structure induced disorder effect. The result is similar to the observation in high Tc superconductors that anisotropy induced fluctuation effect play an important role.