Static dielectric response of charged bosons

Abstract

The dielectric function of a charged Bose gas is determined from the response to an imposed static sinusoidal electric field. Variational and diffusion quantum Monte Carlo simulations are used to calculate the ground-state properties of the system with trial wave functions containing a parameter dependent on the amplitude and wavelength of the perturbation. The induced charge is most efficiently extracted from the difference in ground-state energies at different magnitudes of the external field, rather than directly from the expectation value of the density fluctuation operator. Results are compared to the random-phase approximation for the weakly coupled fluid and to classical lattice values at low densities where the system forms a Wigner crystal. The dielectric function is also calculated at intermediate fluid densities and the transition from positive to negative response is found to occur in the metallic regime.

Monte Carlo simulations of the charged boson fluid atT=0

“…Size effects on the energy difference between the homogeneous and the modulated system have been shown to be very small in Ref. 18.…”

“…The calculation of the static dielectric response ⑀(k,0) follows a somewhat different procedure. 25, 18 We obtain ⑀(k,0) from the static linear density response function (k) via the relationship 1/⑀(k,0)ϭ1ϩv c (k)(k), where v c (k)ϭ4e 2 /k 2 is the Coulomb coupling. In evaluating (k) one perturbs the otherwise homogeneous many-body system with a static external potential v ext ͑ r͒ϭ2v k cos͑k•r͒.…”

“…18 Data on the pair distribution function g(r) are also available. 19 The main purpose of this work is to present extensive results on the static dielectric function, which has been studied earlier in a very limited range of wave numbers, and on the momentum distribution, for which the only published results have come from variational Monte Carlo.…”

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

“…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 .…”

Quantum Monte Carlo study of the dipole moment of CO

“…At present an alternative treatment using stochastic methods is hampered by technical difficulties inherent in the quantum Monte Carlo ͑QMC͒ method. Despite successes in calculating static response properties for homogeneous systems [4][5][6][7] there are only few applications to atoms and molecules. These include the static dipole polarizabilities of He and H 2 , 8 as well as the dipole moment of LiH.…”