Universal Saturation of Intrinsic Electron Dephasing in Three-dimensional Disordered Metals

We have systematically investigated the low-temperature electron dephasing times τ φ in more than 40 three-dimensional polycrystalline impure metals with distinct material characteristics. In all cases, a saturation of the dephasing time is observed below about a (few) degree(s) Kelvin, depending on samples. The value of the saturated dephasing time τ 0 [≡ τ φ (T → 0 K)] falls basically in the range 0.005 to 0.5 ns for all samples. Particularly, we find that τ 0 scales with the electron diffusion constant D as τ 0 ∼ D −α , with α close to or slightly larger than 1, for over two decades of D from about 0.1 to 10 cm 2 /s. Our observation suggests that the saturation behavior of τ φ is universal and intrinsic in three-dimensional polycrystalline impure metals. A complete theoretical explanation is not yet available.