Evidence for a disorder driven phase transition in the condensation of 4He in aerogels

TL;DR

This study investigates how disorder influences the phase transition of helium-4 condensation in silica aerogels, revealing a disorder-driven transition in certain microstructures consistent with theoretical models.

Contribution

It provides experimental evidence for a disorder-driven phase transition in helium-4 condensation within silica aerogels, supporting recent theoretical predictions.

Findings

Disorder affects the shape of adsorption isotherms.

A disorder-driven transition is observed in base-catalysed aerogels.

No transition is observed in neutral-catalysed aerogels.

Abstract

We report on thermodynamic and optical measurements of the condensation process of $^4$He in three silica aerogels of different microstructures. For the two base-catalysed aerogels, the temperature dependence of the shape of adsorption isotherms and of the morphology of the condensation process show evidence of a disorder driven transition, in agreement with recent theoretical predictions. This transition is not observed for a neutral-catalysed aerogel, which we interpret as due to a larger disorder in this case.