Figure 3

(a) Sketches of the ion crystal configurations; (b) Structural phase transitions of 10 and 13 ions with respect to the anisotropic parameter α of the trapping potential, where with the center-to-center distance of two outermost ions in x(z)-axis. From the left to right, the abrupt raising occurs at the phase transitions from the linear to zigzag (α < 0.15), from the zigzag to the ellipse encircling a single ion or an ion string (0.2 < α < 0.3) and then to more complicated configurations with the concentric ellipses (α > 0.5), respectively. The simulation curves are plotted based on .