# Structure of inert layer 4He adsorbed on a mesoporous silica

## TL;DR

This study investigates the structure and phase behavior of inert layer 4He adsorbed on mesoporous silica, revealing coexistence of localized solid and excited fluid phases and suggesting solidification near superfluid transition density.

## Contribution

It provides a detailed analysis of the phase coexistence and structural properties of 4He adsorbed on mesoporous silica using vapor pressure and heat capacity measurements.

## Key findings

- Heat capacity exhibits a Schottky-like peak indicating localized solid to fluid excitation.
- Localized solid and excited fluid coexist at high temperatures.
- Inert layer likely solidifies just below the superfluid transition density.

## Abstract

We have studied the structure of inert layer 4He adsorbed on mesoporous silica (FSM-16), by the vapor pressure and heat capacity measurements. The heat capacity shows a Schottky-like peak due to the excitation of a part of localized solid to fluid. We analyzed the heat capacity over a wide temperature region based on the model including the contribution of the localized solid and excited fluid and clarified that the excited fluid coexists with the localized solid at high temperature. As the areal density approaches the value at which superfluid appears (n_C), the fluid amount is likely to go to zero, suggesting a possibility that the inert layer is solidified just below n_C.