Saturation of electron dephasing in three-dimensional polycrystalline 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 τ₀ [≡τ_ϕ(T→0 K)] falls basically in the range 0.005 to 0.5 ns for all samples. Particularly, we find that τ₀ scales with the electron diffusion constant D as τ₀~D^-α, with α close to or slightly larger than 1, for over two decades of D from about 0.1 to 10 cm² s^-1. Our observation implies an essentially constant saturated dephasing length of (Dτ₀)^1/2~ 1000 Å in three-dimensional polycrystalline disordered metals. A complete theoretical explanation is not yet available.