Monte Carlo simulations of the charged boson fluid atT=0

Abstract

The diffusion Monte Carlo ͑DMC͒ method is used to analyze various properties of the three-dimensional plasma of charged bosons in the homogeneous fluid regime, over the density range 1рr s р160 extending from the so-called uniform limit (r s Ͻ1) to the crystalline phase (r s Ͼ160). The data on the static density response function (k) extend to intermediate and high wave number k the work of Sugiyama, Bowen, and Alder ͓Phys. Rev. B 46, 13 042 ͑1992͔͒ and allow us to extract the static local-field factor G(k) for exchange and correlation. The DMC results for the momentum distribution n(k) show that the condensate fraction decreases with increasing coupling strength from 83% at r s ϭ1 to less than 1% at r s ϭ160. We also present results for the ground-state energy E g (r s ) and for the structure factor S(k). The results for E g (r s ), n(k), and (k) are summarized in analytic interpolation formulas embodying the known asymptotic behaviors. A rigorous upper bound on the plasmon dispersion curve is obtained from the DMC data through a sum-rule argument.

Quasicondensate and superfluid fraction in the two-dimensional charged boson gas at finite temperature

“…for n 0 /n close to unity, in line of principle). This statement is quantitatively tested in Table I, where we compare our results for n 0 /n at T = 0 with the DMC data of Moroni et al 25 over the whole fluid range up to Wigner crystallization. It is clear from Table I that, rather surprisingly, the Bogoliubov approach is almost fully quantitative up to r s ≃ 5, i.e.…”

“…By comparison of results on the 3D fluid with diffusion Monte Carlo data 25 we have found that the Bogoliubov approach may yield quantitatively useful predictions over a surprisingly wide range of coupling strengths and of deviations of the condensate fraction from unity. At finite temperature the behaviour of the charged 2D gas is qualitatively wholly similar to that of its better known neutral analogue: well below the Kosterlitz-Thouless transition a slow power-law decay is seen in the one-body density matrix, heralding extended-range correlations in phase fluctuations and the formation of a condensate over regions of finite size.…”

“…(20) ρ(r) →ñ 0 (r/L) −α (25) with the value of the exponent given by Figure 2 (bottom panels) evidentiates the power-law decay of the density matrix by plotting the curves in log-log scale, as compared with the aympotic behaviour predicted by Eqs. (25) and (26) (dots in the Figure).…”

“…Both variational calculations based on Jastrow-Feenberg wave functions [13][14][15][16][17][18] and self-consistent treatments of correlations [19][20][21] have subsequently been used to evaluate the intermediate and strong coupling regime. Quantal Monte Carlo studies of the 3D-CBF 16,[22][23][24][25] have covered the whole range of coupling strength up to the regime of Wigner crystallization driven by the Coulomb repulsions. Extensive data on the condensate fraction and the momentum distribution in dependence of the coupling strength have become available through the diffusion Monte Carlo (DMC) work of Moroni et al 25 .…”

“…Quantal Monte Carlo studies of the 3D-CBF 16,[22][23][24][25] have covered the whole range of coupling strength up to the regime of Wigner crystallization driven by the Coulomb repulsions. Extensive data on the condensate fraction and the momentum distribution in dependence of the coupling strength have become available through the diffusion Monte Carlo (DMC) work of Moroni et al 25 .…”