# Elastic Anomaly of Thin Neon Film

## TL;DR

This study investigates the elastic properties of thin neon films adsorbed on porous glass, revealing a temperature-induced crossover from fluidlike to solidlike states and suggesting a universal elastic anomaly in atomic or molecular films.

## Contribution

It provides the first measurement of neon film elasticity at low temperatures and compares its behavior to helium films, highlighting differences in quantum phase transition signatures.

## Key findings

- Neon films exhibit an anomalous increase in shear modulus at low temperatures.
- The dissipation peak temperature remains constant around 5 K, unlike helium films.
- Neon films behave as classical systems without quantum phase transitions.

## Abstract

Adsorbed molecular films provide two-dimensional systems that show various emergent phenomena that are not observed in bulk counterparts. We have measured the elasticity of thin neon films adsorbed on porous glass down to 1 K by the torsional oscillator technique. The shear modulus of a neon film anomalously increases at low temperatures with excess dissipation. This behavior indicates a crossover from a soft (fluidlike) state at high temperatures to a stiff (solidlike) state at low temperatures. The temperature dependence of the anomaly is qualitatively similar to that of the elastic anomaly of helium films found in our recent study. The dissipation peak temperature, however, becomes constant at about 5 K, contrary to the case of helium, in which it decreases to 0 K at a critical coverage of a quantum phase transition between a gapped localized phase and a mobile (superfluid) phase. It is concluded that neon films behave as a classical system that does not show a quantum phase transition or superfluidity, although the films may be strongly supercooled to temperatures much lower than the bulk triple point, 24.6 K. Our results suggest that the elastic anomaly is a universal phenomenon of atomic or molecular films adsorbed on disordered substrates.