BOSE–EINSTEIN CONDENSATION IN BULK AND CONFINED SOLID HELIUM

2006 ◽  
Vol 20 (30n31) ◽  
pp. 5081-5092 ◽  
Author(s):  
L. REATTO ◽  
M. ROSSI ◽  
D. E. GALLI
Keyword(s):  
Wave Function ◽  
Ground State ◽  
Solid Helium ◽  
System Size ◽  
Einstein Condensation ◽  
Cylindrical Pore ◽  
Simulated System ◽  
The One ◽  
Bose Einstein ◽  
Energy Computation

We address the question if the ground state of solid 4 He 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 4 He confined in a narrow cylindrical pore are also discussed.

BOSE–EINSTEIN CONDENSATION AND EXCITATIONS IN SOLID 4He WITH VACANCIES

2003 ◽  
Vol 17 (28) ◽  
pp. 5243-5253
Author(s):  
D. E. GALLI ◽  
L. REATTO
Keyword(s):  
Wave Function ◽  
Ground State ◽  
Perfect Crystal ◽  
Function Technique ◽  
Einstein Condensation ◽  
Solid 4He ◽  
Bose Einstein Condensation ◽  
Finite Concentration ◽  
Bose Einstein ◽  
First Time

We have studied the ground state and excited state properties of solid 4 He on the basis of the variational shadow wave function technique (SWF), which allows for relaxation and delocalisation of vacancies. We have found that a finite concentration of vacancies, if present, induces Bose-Einstein condensation (BEC) of the atoms at density close to the T=0 K melting where vacancies are delocalised. No BEC is present in a perfect crystal or in a defected solid at higher densities. We have extended this technique to study longitudinal phonons in solid 4 He and to study the vacancy excitation at a finite momentum; we have been able to compute for the first time the vacancy excitation spectrum in solid 4 He at density close to melting. Our results give a band width of about 8 K.

scholarly journals APPLICATIONS OF DENSITY MATRICES IN A TRAPPED BOSE GAS

2006 ◽  
Vol 20 (15) ◽  
pp. 2189-2221 ◽  
Author(s):  
K. CH. CHATZISAVVAS ◽  
S. E. MASSEN ◽  
CH. C. MOUSTAKIDIS ◽  
C. P. PANOS
Keyword(s):  
Quantum Information ◽  
Bose Gas ◽  
Einstein Condensation ◽  
Density Distributions ◽  
Occupation Numbers ◽  
The One ◽  
Bose Einstein ◽  
Jensen Shannon Divergence ◽  
Analytical Expressions ◽  
Short Range Correlations

An overview of the Bose–Einstein condensation of correlated atoms in a trap is presented by examining the effect of interparticle correlations to one- and two-body properties of the above systems at zero temperature in the framework of the lowest order cluster expansion. Analytical expressions for the one- and two-body properties of the Bose gas are derived using Jastrow-type correlation function. In addition numerical calculations of the natural orbitals and natural occupation numbers are also carried out. Special effort is devoted for the calculation of various quantum information properties including Shannon entropy, Onicescu informational energy, Kullback–Leibler relative entropy and the recently proposed Jensen–Shannon divergence entropy. The above quantities are calculated for the trapped Bose gases by comparing the correlated and uncorrelated cases as a function of the strength of the short-range correlations. The Gross–Piatevskii equation is solved, giving the density distributions in position and momentum space, which are employed to calculate quantum information properties of the Bose gas.

MODULATION OF ORDER PARAMETER OF EXCITON BOSE-EINSTEIN CONDENSATE IN A RING

2004 ◽  
Vol 18 (27n29) ◽  
pp. 3797-3802 ◽  
Author(s):  
S.-R. ERIC YANG ◽  
Q-HAN PARK ◽  
J. YEO
Keyword(s):  
Ground State ◽  
Order Parameter ◽  
Weak Magnetic Field ◽  
Random Potential ◽  
Einstein Condensate ◽  
Einstein Condensation ◽  
Random Potentials ◽  
Bose Einstein Condensate ◽  
The Mean ◽  
Bose Einstein

We have studied theoretically the Bose-Einstein condensation (BEC) of two-dimensional excitons in a ring with a random variation of the effective exciton potential along the circumference. We derive a nonlinear Gross-Pitaevkii equation (GPE) for such a condensate, which is valid even in the presence of a weak magnetic field. For several types of the random potentials our numerical solution of the ground state of the GPE displays a necklace-like structure. This is a consequence of the interplay between the random potential and a strong nonlinear repulsive term of the GPE. We have investigated how the mean distance between modulation peaks depends on properties of the random potentials.

A Possible Mechanism of Superconductivity Based on Wigner Crystal and BEC

1999 ◽  
Vol 13 (29n31) ◽  
pp. 3499-3504 ◽  
Author(s):  
JiXin Dai ◽  
Wen Tao ◽  
Peiherng Hor ◽  
Dai XianXi
Keyword(s):  
Ground State ◽  
Wigner Crystal ◽  
Einstein Condensation ◽  
Bose Einstein Condensation ◽  
Mechanism Of Superconductivity ◽  
Bose Einstein

A new possible mechanism is suggested based on the Wigner crystal and Bose–Einstein condensation. Our previous studies on the singular states that Loudon's singular ground state is rejected by the orthogonality criteria. It is shown that 2D Wigner crystal can exist and to be a possible mechanism for HTS.

Possible Bose-Einstein Condensation of Polygonal Clusters in 2D-Materials

2019 ◽  
Vol 297 ◽  
pp. 204-208
Author(s):  
Abid Boudiar
Keyword(s):  
Free Energy ◽  
Critical Temperature ◽  
Ground State ◽  
Low Temperatures ◽  
2D Materials ◽  
Equilibrium Structure ◽  
Einstein Condensation ◽  
Bose Einstein Condensation ◽  
Exchange Approximation ◽  
Bose Einstein

This study investigates the possibility of Bose-Einstein condensation (BEC) in 2D-nanoclusters. A ground state equilibrium structure involves the single phonon exchange approximation. At critical temperature, the specific heat, entropy, and free energy of the system can be determined. The results support the existence of BEC in nanoclusters, and they lead to predictions of the behaviour of 2Dmaterials at low temperatures.

On Bose-Einstein condensation in one-dimensional lattices of delta functions

2020 ◽  
Vol 35 (03) ◽  
pp. 2040005 ◽  
Author(s):  
M. Bordag
Keyword(s):  
Dimensional Case ◽  
Einstein Condensation ◽  
Periodic Lattice ◽  
Spectral Functions ◽  
One Dimensional ◽  
Bose Einstein Condensation ◽  
Free Case ◽  
Delta Functions ◽  
The One ◽  
Bose Einstein

We investigate Bose-Einstein condensation of a gas of non-interacting Bose particles moving in the background of a periodic lattice of delta functions. In the one-dimensional case, where one has no condensation in the free case, we showed that this property persist also in the presence of the lattice. In addition we formulated some conditions on the spectral functions which would allow for condensation.

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