Dimensional Reduction of Helium-4 Inside Argon Plated MCM-41 Nanopores

TL;DR

This study demonstrates a nano-engineering method to confine helium-4 within ultra-narrow pores of MCM-41, enabling exploration of one-dimensional quantum fluids through experimental and simulation techniques.

Contribution

We developed a pre-plating technique with argon to reduce pore size in MCM-41, achieving quasi-one-dimensional helium-4 confinement and validating it with experiments and simulations.

Findings

Argon pre-plating reduces pore diameter to quasi-1D regime.

Experimental adsorption and neutron scattering agree with quantum Monte Carlo simulations.

Confinement potential tunable at angstrom and kelvin scales.

Abstract

The angstrom-scale coherence length describing the superfluid wavefunction of helium-4 at low temperatures has prevented its preparation in a truly one-dimensional geometry. Mesoporous ordered silica-based structures, such as the molecular sieve MCM-41, offer a promising avenue towards physical confinement, but the minimal pore diameters that can be chemically synthesized have proven to be too large to reach the quasi-one-dimensional limit. We present an active nano-engineering approach to this problem by pre-plating MCM-41 with a single, well controlled layer of Ar gas before filling the pores with helium. The structure inside the pore is investigated via experimental adsorption isotherms and neutron scattering measurements that are in agreement with large scale quantum Monte Carlo simulations. The results demonstrate angstrom and kelvin scale tunability of the effective confinement potential experienced by 4He atoms inside the MCM-41, with the Ar layer reducing the diameter of the confining media into a regime where a number of solid layers surround a one-dimensional quantum liquid.