All-optical nanotraps for atoms atop flat metamaterial lenses: a theoretical study.

We propose a novel setup for optically trapping neutral atoms based upon the focusing properties of metamaterials. The optical trap is created at the focal point of an inverted-opal crystal when the latter is illuminated by a localized light source. The trap is located away from the surface of the inverted-opal lens, rendering the Casimir-Polder attraction exerted by the lens on the atom negligible. The key properties of the proposed optical trap are its subwavelength dimensions, the tunability of the trapping frequency, the facile translation of the trap without moving the lens, and the potential for creating an array of traps. We also study the ground state of a cesium Bose-Einstein condensate formed within the proposed trap by solving the corresponding time-independent Gross-Pitaevskii equation.