Comment on ``Point-Contact Study of Fast and Slow Two-Level Fluctuators in Metallic Glasses'' by Keijsers, Shklyarevskii and van Kempen

TL;DR

This paper critiques a recent experiment on metallic glass point contacts, highlighting that it measures individual two-level systems' conductance contributions and comparing theoretical models with experimental data.

Contribution

It clarifies the experimental measurement of individual TLS conductance and evaluates the accuracy of different theoretical models against recent data.

Findings

Vladar-Zawadowski theory aligns better with experimental results.

The experiment effectively measures conductance of single TLSs.

Differences between theoretical predictions are highlighted.

Abstract

We point out that a recent experiment by Keijsers, Shklyarevskii and van Kempen [Phys. Rev. Lett. 77, 3411 (1996)] on metallic glass point contacts containing two-level systems (TLS) effectively measures for the first time the conductance contributions of individual TLSs (previous experiments averaged over a distribution of TLSs). For this case the predictions of the Kozub-Kulik theory for the TLS-electron interaction differ from those of the Vladar-Zawadowski theory, the latter giving much better agreement with experiment.