Related papers: Microscopic studies of solid 4He with Path Integra…
We calculate properties of a model of $^4$He in Vycor using the Path Integral Monte Carlo method. We find that $^4$He forms a distinct layered structure with a highly localized first layer, a disordered second layer with some atoms…
The path-integral formulation of the statistical mechanics of quantum many-body systems is described, with the purpose of introducing practicaltechniques for the simulation of solids. Monte Carlo and molecular dynamics methods for…
Path-integral Monte Carlo calculations were performed to study the adsorption of $^4$He atoms on $\alpha$-graphyne. We find that one $^4$He atom can be embedded onto the in-plane center of each hexagon of the graphyne. In the first $^4$He…
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…
Using quantum Monte Carlo we have studied the superfluid density of the first layer of $^4$He and H$_2$ adsorbed on graphene and graphite. Our main focus has been on the equilibrium ground state of the system, which corresponds to a…
The temperature dependence of the one-body density matrix in 4He crystals presenting vacancies is computed with Path Integral Monte Carlo. The main purpose of this study is to estimate the onset temperature T_0 of Bose-Einstein condensation…
We present a first-principles computational study of solid 4He at T=0K and pressures up to 160GPa. Our computational strategy consists in using van der Waals density functional theory (DFT-vdW) to describe the electronic degrees of freedom…
We investigate strongly correlated many-body systems composed of bosons and fermions with a fully quantum treatment using the path-integral ground state method, PIGS. To account for the Fermi-Dirac statistics, we implement the fixed-node…
We are investigating the properties of vacancies in solid 4He with the exact zero temperature SPIGS method. Our aim is to study the possibility of phase--separation between vacancies and the perfect crystal. We find a significant…
This study aims to construct a theoretical formulation of a nonequilibrium process for a system of Bose--Einstein condensate associated with a spontaneous symmetry breakdown. For this, Thermo Field Dynamics is used. We then describe the…
Combining first-principles calculations with a technique for many-body problems, we investigate properties of the transition metal oxide ${\rm Sr_{2}VO_{4}}$ from the microscopic point of view. By using the local density approximation…
By using the diffusion Monte Carlo method, we obtained the full phase diagram of $^3$He on top of graphite preplated with a solid layer of $^4$He. All the $^4$He atoms of the substrate were explicitly considered and allowed to move during…
We present precision neutron scattering measurements of the Bose-Einstein condensate fraction, n0(T), and the atomic momentum distribution, n\star(k), of liquid 4He at pressure p =24 bar. Both the temperature dependence of n0(T) and of the…
The structure and energetics of the free surface of superfluid $^4$He are studied using the diffusion Monte Carlo method. Extending a previous calculation by Vall\'es and Schmidt, which used the Green's function Monte Carlo method, we study…
Path Integral Monte Carlo was used to calculate the Bose-Einstein condensate fraction at the surface of a helium film at $T=0.77 K$, as a function of density. Moving from the center of the slab to the surface, the condensate fraction was…
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…
We analytically investigate the ground-state properties of two-component Bose-Einstein condensates with few ⁸⁷Rb atoms inside a high-quality cavity quantum electrodynamics. In the SU(2) representation for atom, this quantum…
We present results of a theoretical study of 4He films adsorbed on graphite, based on the continuous space worm algorithm. In the first layer, we find a domain-wall phase and a (7/16) registered structure between the commensurate (1/3) and…
The behavior of quantum fluids (4He and H2) within nanopores is explored in various regimes, using several different methods. A focus is the evolution of each fluid's behavior as pore radius R is increased. Results are derived with the path…
Generally ``exact'' Quantum Monte Carlo computations for the ground state of many Bosons make use of importance sampling. The importance sampling is based, either on a guiding function or on an initial variational wave function. Here we…