Intrinsic phase-decoherence of electrons by two-level systems

TL;DR

This paper investigates how two-level systems (TLSs) in disordered mesoscopic systems influence electron phase coherence at very low temperatures, highlighting the role of incoherent tunneling and interactions among TLSs.

Contribution

It introduces a model where incoherent tunneling of TLSs and their interactions affect electron phase decoherence, providing a new perspective on phase saturation at low temperatures.

Findings

Inelastic scattering from TLSs dominates at T→0.

Incoherent tunneling impacts electron phase shifts.

Competition between T-dependent effects governs phase coherence.

Abstract

The fundamental problem of phase saturation of electrons in a disordered mesoscopic system at very low temperatures is addressed. The disorder in the medium has both static and dynamic components, the latter being in the form of two-level systems (TLSs), which becomes just about the only source of inelastic scattering in the limit $T\to 0$. We propose that besides the inelastic nature of scattering from the TLSs, the phase-shift of the electrons is also affected by the nature of tunneling in the TLSs. The tunneling becomes incoherent as $T$ decreases due to increasing long-range interactions among TLSs and affects the phase coherence of electrons scattering from them. The competition between this effect, which increases as $\sim T^{-1}$, and that of the scattering rate $\tau_{e-TLS}^{-1}$ behaving as $\sim T$ apparently governs the phase-shift of electrons.