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

TL;DR

This paper explores how non-magnetic two-level systems in metals, exhibiting non-Fermi-liquid behavior in the 2-channel Kondo regime, can cause apparent saturation of electron dephasing rates at low temperatures, explaining recent experimental observations.

Contribution

It identifies a novel non-universal dephasing mechanism involving TLSs with Kondo physics, expanding understanding of electron coherence in metals.

Findings

TLSs cause dephasing saturation in gold wires

Non-Fermi-liquid effects influence dephasing rates

Dephasing vanishes as temperature approaches zero

Abstract

We point out a novel, non-universal contribution to the dephasing rate 1/\tau_\phi \equiv \gamma_\phi of conduction electrons in metallic systems: scattering off non-magnetic two-level systems (TLSs) having almost degenerate Kondo ground states. In the regime \Delta_{ren} < T < T_K (\Delta_{ren} = renormalized level splitting, T_K = Kondo temperature), such TLSs exhibit non-Fermi-liquid physics that can cause \gamma_\phi, 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)].