Thermodynamic Evidence for Nanoscale Bose-Einstein Condensation in ^4He Confined in Nanoporous Media

TL;DR

This study provides thermodynamic evidence for nanoscale Bose-Einstein condensation of helium-4 confined in nanoporous media, revealing localized condensates through heat capacity measurements.

Contribution

It demonstrates the formation of localized Bose-Einstein condensates in nanoporous media via heat capacity analysis, a novel thermodynamic approach.

Findings

Heat capacity peak indicates LBEC formation

Heat capacity matches phonon and roton excitation models

Supports existence of localized BEC on nanometer scales

Abstract

We report the measurements of the heat capacity of ^4He confined in nanoporous Gelsil glass that has nanopores of 2.5-nm diameter at pressures up to 5.3 MPa. The heat capacity has a broad peak at a temperature much higher than the superfluid transition temperature obtained using the torsional oscillator technique. The peak provides a definite thermodynamic evidence for the formation of localized Bose-Einstein condensates (LBECs) on nanometer length scales. The temperature dependence of heat capacity is well described by the excitations of phonons and rotons, supporting the existence of LBEC.