Direct Evidence for a Two-component Tunnelling Mechanism in the Multicomponent Glasses at Low Temperatures

TL;DR

This paper provides direct evidence for a two-component tunneling mechanism in multicomponent glasses at low temperatures, extending the traditional two-level systems model to include multilevel tunneling systems to explain magnetic effects and mixed glass behaviors.

Contribution

The study introduces a generalized tunneling model incorporating multilevel systems to explain low-temperature anomalies and magnetic effects in multicomponent glasses.

Findings

Evidence for multilevel tunneling systems in glasses.

Extension of the tunneling model to account for magnetic effects.

Development of new two-level systems via dilution near SiO4 clusters.

Abstract

The dielectric anomalies of window-type glasses at low temperatures ($T<$ 1 K) are rather successfully explained by the two-level systems (2LS) tunneling model (TM). However, the magnetic effects discovered in the multisilicate glasses in recent times \cite{ref1}-\cite{ref3}, and also some older data from mixed (SiO$_2$)$_{1-x}$(K$_2$O)$_x$ and (SiO$_2$)$_{1-x}$(Na$_2$O)$_x$ glasses \cite{ref4}, indicate the need for a suitable generalization of the 2LS TM. We show that, not only for the magnetic effects \cite{ref3,ref5} but also for the mixed glasses in the absence of a field, the right extension of the 2LS TM is provided by the (anomalous) multilevel tunneling systems approach proposed by one of us. It appears that new 2LS develop via dilution near the hull of the SiO$_4$-percolating clusters in the mixed glasses.