Dielectric constant of glasses: first observation of a two-dimensional behavior

TL;DR

This study measures the dielectric constant of glasses at very low temperatures and finds that reducing sample thickness reveals a two-dimensional behavior, challenging existing models and highlighting the importance of interactions.

Contribution

It demonstrates that TLS-TLS interactions cause a two-dimensional behavior in dielectric response when sample thickness is reduced to nanometer scales.

Findings

Suppression of the dielectric constant minimum at small thicknesses.

Two-dimensional behavior observed in thin samples.

Interactions are crucial in understanding dielectric properties.

Abstract

The 1kHz real part $\chi'$ of the dielectric constant of a structural glass was measured at low temperature $T$ down to 14 mK. Reducing the sample thickness $h$ to 10 nm suppresses the usual minimum of $\chi'$ for measuring fields $E<.5 $ MV/m. This contradicts the Two Level System (TLS) model but is well accounted for by including TLS-TLS interactions where excitations delocalize between TLS's through a $E$-induced mechanism recently designed: for small $h$'s this interaction is reduced, which explains the two-dimensional behavior of $\chi'(T)$. Hence, interactions play a key role in standard thick samples.