Dynamics of Tunneling Centers in Metallic Systems

TL;DR

This paper investigates the dynamics of tunneling centers in metals using bosonization, revealing how electron-assisted tunneling affects relaxation rates and could be observed experimentally at low temperatures.

Contribution

It introduces a detailed analysis of electron-assisted tunneling in metallic systems, extending previous models to include this process and its impact on tunneling dynamics.

Findings

Relaxation rate per temperature increases steeply at low temperatures.

Electron-assisted tunneling alters the renormalized tunneling frequency.

Predicted observable effects in low-temperature experiments.

Abstract

Dynamics of tunneling centers (TC) in metallic systems is studied, using the technique of bosonization. The interaction of the TC with the conduction electrons of the metal involves two processes, namely, the screening of the TC by electrons, and the so-called electron assisted tunneling. The presence of the latter process leads to a different form of the renormalized tunneling frequency of the TC, and the tunneling motion is damped with a temperature dependent relaxation rate. As the temperature is lowered, the relaxation rate per temperature shows a steep rise as opposed to that in the absence of electron assisted process. It is expected that this behavior should be observed at very low temperatures in a careful experiment. The present work thus tries to go beyond the existing work on the {\it dynamics} of a two-level system in metals, by treating the electron assisted process.