Spectral diffusion on ultralong time scales in low temperature glasses

TL;DR

This paper develops a dynamical theory for spectral diffusion in low-temperature glasses over long times, highlighting the role of interacting tunneling centers and proposing experimental tests to validate the theory.

Contribution

It introduces a new dynamical model involving interacting tunneling centers to explain spectral diffusion in glasses near 1 Kelvin, addressing deviations from standard models.

Findings

The theory accounts for non-logarithmic line broadening in spectral diffusion.

Interacting tunneling centers significantly influence spectral hole width.

Proposed experiments can distinguish between competing theories.

Abstract

A dynamical theory is constructed to describe spectral diffusion in glasses in the temperature range near 1 Kelvin on long time scales. The theory invokes interacting tunneling centers (TLS) which provide an excess contribution to the spectral hole width which qualitatively accounts for the deviation from standard logarithmic line broadening observed by Maier et al. [Phys. Rev. Lett. 76, 2085 (1996)]. Alternative explanation schemes of the nonlogarithmic line broadening, avoiding interacting TLS, are discussed. We devise experimental tests which could be used to access the validity of the proposed theories.