We address the question if the ground state of solid 4He has the number of lattice sites equal to the number of atoms (commensurate state) or if it is different (incommensurate state). We point out that energy computation from simulation as performed by now cannot be used to decide this question and that the presently best variational wave function, a shadow wave function, gives an incommensurate state. We have extended the calculation of the one–body density matrix ρ1 to the exact Shadow Path Integral Ground State method. Calculation of ρ1 at ρ = 0.031 Å-3 shows that Vacancy–Interstitial pair processes are present also in the exact computation but the simulated system size is too small to infer the presence of off–diagonal long range order. Variational simulations of 4He confined in a narrow cylindrical pore are also discussed.
Bose-Einstein condensation in bulk and confined solid helium / L. Reatto, M. Rossi, D.E. Galli. - In: INTERNATIONAL JOURNAL OF MODERN PHYSICS B. - ISSN 0217-9792. - 20:30-31(2006), pp. 5081-5092.
Bose-Einstein condensation in bulk and confined solid helium
L. ReattoPrimo
;M. RossiSecondo
;D.E. GalliUltimo
2006
Abstract
We address the question if the ground state of solid 4He has the number of lattice sites equal to the number of atoms (commensurate state) or if it is different (incommensurate state). We point out that energy computation from simulation as performed by now cannot be used to decide this question and that the presently best variational wave function, a shadow wave function, gives an incommensurate state. We have extended the calculation of the one–body density matrix ρ1 to the exact Shadow Path Integral Ground State method. Calculation of ρ1 at ρ = 0.031 Å-3 shows that Vacancy–Interstitial pair processes are present also in the exact computation but the simulated system size is too small to infer the presence of off–diagonal long range order. Variational simulations of 4He confined in a narrow cylindrical pore are also discussed.Pubblicazioni consigliate
I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.