It is pointed out that the simulation computation of energy performed so far cannot be used to decide if the ground state of solid He-4 has the number of lattice sites equal to the number of atoms (commensurate state) or if it is different (incommensurate state). The best variational wave function, a shadow wave function, gives an incommensurate state, but the equilibrium concentration of vacancies remains to be determined. We have computed the one-body density matrix in solid He-4 for the incommensurate state by means of an exact ground state projector method in which incommensurability occurs spontaneously. We find a vacancy induced Bose-Einstein condensation of about 0.23 atoms per vacancy at a pressure of 54 bar. This means that bulk solid He-4 is supersolid at low enough temperature if the exact ground state is incommensurate.
Bose-Einstein condensation of incommensurate solid He-4 / D.E. Galli, L. Reatto. - In: PHYSICAL REVIEW LETTERS. - ISSN 0031-9007. - 96:16(2006), pp. 165301.165301_1-165301.165301_4.
Bose-Einstein condensation of incommensurate solid He-4
D.E. GalliPrimo
;L. ReattoUltimo
2006
Abstract
It is pointed out that the simulation computation of energy performed so far cannot be used to decide if the ground state of solid He-4 has the number of lattice sites equal to the number of atoms (commensurate state) or if it is different (incommensurate state). The best variational wave function, a shadow wave function, gives an incommensurate state, but the equilibrium concentration of vacancies remains to be determined. We have computed the one-body density matrix in solid He-4 for the incommensurate state by means of an exact ground state projector method in which incommensurability occurs spontaneously. We find a vacancy induced Bose-Einstein condensation of about 0.23 atoms per vacancy at a pressure of 54 bar. This means that bulk solid He-4 is supersolid at low enough temperature if the exact ground state is incommensurate.Pubblicazioni consigliate
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