Quasi-one-dimensional $^4$He in nanopores

TL;DR

This study uses Quantum Monte Carlo simulations to explore the low-temperature structural and superfluid properties of helium-4 confined in nanopores, revealing persistent one-dimensional behavior regardless of pore size or shell formation.

Contribution

It demonstrates that helium-4 in nanopores exhibits robust one-dimensional behavior, challenging previous claims of dimensional crossover in such systems.

Findings

Helium-4 forms either a single channel or concentric shells inside nanopores.

The system maintains one-dimensional physics even with shell formation.

No dimensional crossover occurs above certain pore sizes.

Abstract

Low temperature structural and superfluid properties of $^4$He confined in cylindrical nanopores are theoretically investigated by means of first principle Quantum Monte Carlo (QMC) simulations. We vary the density of $^4$He inside the pore, as well as the pore diameter and the potential describing the interaction of each $^4$He atom with the pore surface. Accordingly, the $^4$He fluid inside the pore forms either a single channel along the axis, or a series of concentric cylindrical shells, with varying degrees of shell overlap. In the limit of pore length greatly exceeding its radius, the $^4$He fluid always displays markedly one-dimensional behavior, with no "dimensional crossover" above some specific pore radius and/or as multiple concentric shells form, in contrast to what recently claimed by other authors [Phys. Rev. B 101, 104505 (2020)]. Indeed, the predicted robustness of one-dimensional physics suggests that this system may offer a broadly viable pathway to the experimental observation of exotic behavior of, e.g., junctions of interacting Tomonaga-Luttinger liquids, in an appropriately designed network of nanopores.