Related papers: Microscopic approach to the bcc phase of solid 4He
The thermodynamics of solid (hcp) He-4 is studied theoretically by means of unbiased Monte Carlo simulations at finite temperature, in a wide range of density. This study complements and extends previous theoretical work, mainly by…
The lattice dynamics of hcp crystalline 4He is studied at zero temperature and for two different densities (near and far from melting), using a ground-state path-integral quantum Monte Carlo technique. The complete phonon dispersion is…
Solid helium (3He and 4He) in the hcp and fcc phases has been studied by path-integral Monte Carlo. Simulations were carried out in the isothermal-isobaric (NPT) ensemble at pressures up to 52 GPa. This allows one to study the temperature…
The kinetics of HCP-BCC structure phase transition is studied by precise pressure measurement technique in 4He crystals of different quality. An anomalous pressure behavior in bad quality crystals under constant volume conditions is…
We report neutron diffraction studies of low density bcc and hcp solid 4He. In the bcc phase, we observed a continuous dynamical behaviour involving macroscopic structural changes of the solid. The dynamical behaviour takes place in a cell…
Using Path Integral Monte Carlo and the Maximum Entropy method, we calculate the dynamic structure factor of solid $^4$He in the bcc phase at a finite temperature of T = 1.6 K and a molar volume of 21 cm$^3$. Both the single-phonon…
Displacements of atoms and molecules away from lattice sites in helium and parahydrogen solids at low temperature have been studied by means of Quantum Monte Carlo simulations. In the bcc phases of He-3 and He-4, atomic displacements are…
Using Path Integral Monte Carlo we calculate exchange frequencies in bulk hcp 4He as atoms undergo ring exchange. We fit the frequencies to a lattice model and examine whether such atoms could become a supersolid, that is have a…
The elastic constants of hcp $^{4}$He are computed using the path-integral Monte Carlo (PIMC) method. The stiffness coefficients are obtained by imposing different distortions to a periodic cell containing 180 atoms, followed by measurement…
In this work we investigate the quantum nature of bcc $^{4}$He. We show that it is a solid phase with an Off-Diagonal Long Range Order of coherently oscillating local electric dipole moments. These dipoles arise from the correlated…
We study the elasticity of perfect 4He at zero-temperature using the diffusion Monte Carlo method and a realistic semi-empirical pairwise potential to describe the He-He interactions. Specifically, we calculate the value of the elastic…
Lattice-switch Monte Carlo is an efficient method for calculating the free energy difference between two solid phases, or a solid and a fluid phase. Here, we provide a brief introduction to the method, and list its applications since its…
We perform calculations of the momentum distribution n(k) in solid \^4\He by means of path integral Monte Carlo methods. We see that, in perfect crystal, n(k) does not depend on temperature T and that is different from the classical…
The ground state of solid $^4$He is studied using the diffusion Monte Carlo method and a new trial wave function able to describe the supersolid. The new wave function is symmetric under the exchange of particles and reproduces the…
In this work we investigate implications of the quantum nature of bcc $^{4}$% He. We show that it is a unique solid phase with both a lattice structure and an Off-Diagonal Long Range Order of coherently oscillating local electric dipole…
The compressibility of solid helium (3He and 4He) in the hcp and fcc phases has been studied by path-integral Monte Carlo. Simulations were carried out in both canonical (NVT) and isothermal-isobaric (NPT) ensembles at temperatures between…
We have investigated the ground state properties of solid $^4$He with the Shadow Path Integral Ground State method. This exact T=0 K projector method allows to describes quantum solids without introducing any a priori equilibrium position.…
By use of a novel experimental design, one that provides for superfluid helium in contact with bulk hcp 4He off the melting curve, we have observed the DC transport of mass through a cell filled with solid 4He in the hcp region of the phase…
In a recent study we have reported a new type of trial wave function symmetric under the exchange of particles and which is able to describe a supersolid phase. In this work, we use the diffusion Monte Carlo method and this model wave…
Recently there have been experimental indications that solid 4He might be a supersolid. We discuss the relation of supersolid behavior to ring exchange. The tunnelling frequencies for ring exchanges in quantum solids are calculated using…