Minimum energy state of the one-dimensional Coulomb chain

One-dimensional chains of laser-cooled ions have recently been confined in the fields of electromagnetic traps. This paper considers the minimum energy states of this one-dimensional (1D) form of condensed matter. Molecular dynamics simulations of the minimum energy states are compared to a density functional theory of the inhomogeneous crystal. Unlike 2D and 3D inhomogeneous Coulombic systems, where mean-held theory works well in describing the overall density variation on scales large compared to an interparticle spacing, we show that correlations are essential in determining the density of the 1D Coulomb chain. On the other hand, the long-range interactions that contribute to the mean field must also be kept.