Electron-assisted relaxation of tunneling systems in polycrystalline aluminium

摘要

Vibrating reed measurements are presented of pure poly-crystalline Al with a special sample shape that reduces the influence of the clamping. We find significant differences between the sample being normal conducting or superconducting. The overall behaviour in fact resembles very closely that of metallic glasses and clearly demonstrates that also in Al tunneling systems couple to conduction electrons as expected. As a quantitative result we may state that the density of states of tunneling systems in poly-crystalline Al is considerably smaller than in metallic glasses.