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.

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.

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.

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.

Cooper Pairing and Ladder Correlations in a BCS Ground State

2003 ◽  
Vol 17 (18n20) ◽  
pp. 3304-3309
Author(s):  
V. C. Aguilera-Navarro ◽  
M. Fortes ◽  
M. de Llano
Keyword(s):  
Ground State ◽  
Center Of Mass ◽  
Two Dimensions ◽  
Einstein Condensation ◽  
Positive Energy ◽  
Cooper Pairs ◽  
Linear Dispersion ◽  
Bose Einstein Condensation ◽  
Leading Term ◽  
Bose Einstein

A Bethe–Salpeter treatment of Cooper pairs (CPs) based on an ideal Fermi gas (IFG) "sea" produces unstable CPs if holes are not ignored. Stable CPs with damping emerge when the BCS ground state replaces the IFG, and are positive-energy, finite-lifetime resonances for nonzero center-of-mass momentum with a linear dispersion leading term. Bose–Einstein condensation of such pairs may thus occur in exactly two dimensions as it cannot with quadratic dispersion.

Bose-Einstein Condensation in a Dilute Gas: Measurement of Energy and Ground-State Occupation

1996 ◽  
Vol 77 (25) ◽  
pp. 4984-4987 ◽  
Author(s):  
J. R. Ensher ◽  
D. S. Jin ◽  
M. R. Matthews ◽  
C. E. Wieman ◽  
E. A. Cornell
Keyword(s):  
Ground State ◽  
Einstein Condensation ◽  
Bose Einstein Condensation ◽  
Dilute Gas ◽  
Gas Measurement ◽  
Bose Einstein

An experiment to detect vacancies and their possible Bose-Einstein condensation in solid 4He

1992 ◽  
Vol 86 (5-6) ◽  
pp. 349-362 ◽  
Author(s):  
P. G. van de Haar ◽  
C. M. C. M. van Woerkens ◽  
M. W. Meisel ◽  
G. Frossati
Keyword(s):  
Einstein Condensation ◽  
Solid 4He ◽  
Bose Einstein Condensation ◽  
Bose Einstein
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