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

Abstract

We point out a novel, non-universal contribution to the dephasing rate 1/τ_ϕ\equiv γ_ϕof conduction electrons in metallic systems: scattering off non-magnetic two-level systems (TLSs) having almost degenerate Kondo ground states. In the regime Δ_{ren} < T < T_K (Δ_{ren} = renormalized level splitting, T_K = Kondo temperature), 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 \to 0. This could explain the saturation of dephasing recently observed in gold wires [Mohanty et al. Phys. Rev. Lett. 78, 3366 (1997)].