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Published on: August 2, 2019
Ground-state properties and superfluidity of two- and quasi-two-dimensional solid 4He
C Cazorla1, G E Astrakharchik, J Casulleras
1Department of Chemistry, University College London, London WC1H 0AH, UK. c.silva@ucl.ac.uk
Summary
Researchers explored solid helium-4 (4He) in 2D and quasi-2D forms using diffusion Monte Carlo. They found that 2D helium-4 has negligible superfluid density, but quasi-2D helium-4 exhibits finite superfluidity.
Area of Science:
- Quantum Mechanics
- Condensed Matter Physics
Background:
- Supersolid phases represent exotic quantum states of matter.
- Previous models described supersolid phases using trial wavefunctions.
- Understanding helium-4's behavior in reduced dimensions is crucial for quantum physics.
Purpose of the Study:
- To investigate the properties of solid helium-4 (4He) in two-dimensional (2D) and quasi-two-dimensional (quasi-2D) geometries.
- To determine the superfluid fraction in these geometries using diffusion Monte Carlo methods.
- To explore the coexistence of superfluidity and crystalline order.
Main Methods:
- Utilized the diffusion Monte Carlo (DMC) method.
- Employed a novel trial wavefunction symmetric under particle exchange.
- Calculated ground-state energy, freezing/melting densities, and superfluid fraction (ρ(s)/ρ).
Main Results:
- Results for 2D solid 4He (ground-state energy, freezing/melting densities) align with prior Monte Carlo calculations.
- The superfluid fraction in purely 2D solid 4He was found to be negligible.
- Quasi-2D solid 4He exhibited a finite superfluid density alongside its crystalline structure.
Conclusions:
- Purely 2D solid helium-4 does not display significant superfluidity, similar to defect-free 3D crystals.
- Allowing local atomic motion perpendicular to the 2D plane induces superfluidity in quasi-2D solid helium-4.
- This suggests that reduced dimensionality and atomic mobility influence the emergence of supersolid properties.
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