Bounds for the Superfluid Fraction from Exact Quantum Monte Carlo Local Densities

TL;DR

This paper uses exact quantum Monte Carlo calculations of local densities to estimate upper bounds for the superfluid fraction in solid helium-4 and p-H2, revealing significant discrepancies with experimental observations.

Contribution

It introduces a method combining flow-energy-minimizing phase functions with Monte Carlo data to calculate superfluid bounds, highlighting the need for improved theoretical models.

Findings

Superfluid fraction bounds are less than 0.20-0.21 at melting pressure for solid 4He.

Calculated bounds are about ten times higher than experimental values.

Current theoretical approaches require substantial improvements.

Abstract

For solid 4He and solid p-H2, using the flow-energy-minimizing one-body phase function and exact T=0 K Monte Carlo calculations of the local density, we have calculated the phase function, the velocity profile and upper bounds for the superfluid fraction f_s. At the melting pressure for solid 4He we find that f_s < 0.20-0.21, about ten times what is observed. This strongly indicates that the theory for the calculation of these upper bounds needs substantial improvements.