Fig. 2.

Comparison of voltage fluctuation C₀(r_s,a) using different screening approximations. The RPA is the main approximation used in the present work. The Thomas–Fermi result was derived in ref. 30 and the “complete screening” result valid for r_sa ≫ 1, was obtained in ref. 29. All three approximations agree in the large-density limit, but disagree for small density. Shown in dashed lines are small-density analytic asymptotes for the Thomas–Fermi and RPA and squares show the numerical evaluation of Eq. 7 by using the exact dielectric function reported in ref. 41.