Dephasing in Metals by Two-Level Systems in the 2-Channel Kondo Regime

We point out a novel, nonuniversal contribution to the dephasing rate 1/τ_φ≡γ_φ of conduction electrons in metallic systems: scattering off nonmagnetic two-level systems (TLSs) having almost degenerate Kondo ground states. In the regime Δᵣₑₙ<T<TK ( Δᵣₑₙ0ex0ex=0ex0exrenormalizedlevelsplitting, TK0ex0ex=0ex0exKondotemperature), such TLSs exhibit non-Fermi-liquid physics that can cause γ_φ, which generally decreases with decreasing T, to seemingly saturate in a limited temperature range before vanishing for T→0. This could explain the saturation of dephasing recently observed in gold wires [Mohanty et al., Phys. Rev. Lett. 78, 3366 (1997)].