Superfluidity of dense 4He in vycor

Area of Science:

• Condensed matter physics
• Quantum fluids

Background:

• Solid 4He confined in porous media like Vycor exhibits unusual superfluid properties.
• Understanding the microscopic structure and dynamics is key to explaining its behavior.

Purpose of the Study:

• To investigate the structural properties and superfluidity of 4He in Vycor using advanced computational methods.
• To elucidate the role of layer-specific atomic arrangements in observed superfluid responses.

Main Methods:

• Path integral Monte Carlo (PIMC) simulations were employed to model 4He within a Vycor matrix.
• Analysis focused on atomic localization, delocalization, and inter-layer exchange processes.

Main Results:

• A distinct layered structure was identified: a localized first layer, a disordered second layer with delocalized atoms responsible for superfluidity, and crystalline higher layers.
• The introduction of a single Helium-3 (3He) atom significantly suppressed superfluidity by disrupting exchange in the second layer.

Conclusions:

• The findings support the persistent liquid-layer model for explaining superfluidity in confined 4He.
• This model may also apply to bulk solid 4He with grain boundaries, offering insights into macroscopic quantum phenomena.