Bcc 4^4He as a Coherent Quantum Solid

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 moments. These dipoles arise from the local motion of the atoms in the crystal potential well, and oscillate in synchrony to reduce the dipolar interaction energy. The dipolar ground-state is therefore found to be a coherent state with a well defined global phase and a three-component complex order parameter. The condensation energy of the dipoles in the bcc phase stabilizes it over the hcp phase at finite temperatures. We further show that there can be fermionic excitations of this ground-state and predict that they form an optical-like branch in the (110) direction. A comparison with 'super-solid' models is also discussed.Comment: 12 pages, 8 figure

Variational Monte Carlo study of the ground state properties and vacancy formation energy of solid para-H2 using a shadow wave function

A Shadow Wave Function (SWF) is employed along with Variational Monte Carlo techniques to describe the ground state properties of solid molecular para-hydrogen. The study has been extended to densities below the equilibrium value, to obtain a parameterization of the SWF useful for the description of inhomogeneous phases. We also present an estimate of the vacancy formation energy as a function of the density, and discuss the importance of relaxation effects near the vacant site

QUANTUM THEOREM OF CORRESPONDING STATES AND SPIN-POLARIZED QUANTUM SYSTEM

On donne une revue des propriétés thermodynamiques des systèmes quantiques macroscopiques du point de vue du Théorème Quantique des Etats Correspondants. Ces résultats sont utilisés pour prédire et discuter les propriétés thermodynamiques des systèmes quantiques spin-polarisés.A review of the thermodynamic properties of macroscopic quantum systems is given from the unified point of view provided by the Quantum Theorem of Corresponding States. These results are used to predict and discuss the thermodynamic properties of spin-polarized quantum systems