Casimir-Polder force on a two-level atom in a structure containing metamaterials

Abstract

We study the Casimir-Polder (CP) force on an excited cold two-level atom in structures containing metamaterials. We adopt two kinds of metamaterials: left-handed materials (LHMs) and zero-index materials (ZIMs). The CP force on an excited atom can be divided into two parts: the dispersive force that responds to all frequencies of the electromagnetic mode and the resonant force, which is determined by the frequency at the atomic transition. Left-handed materials and ZIMs can significantly modify the resonant part of the CP force due to their unique character. It is found here that the presence of LHMs can enhance the force on the atom far away from the surface due to its phase compensation, while the presence of ZIMs can lead to a force that is independent of dipole orientation. The Casimir effect within the combination of LHMs and ZIMs leads us to realize a potential well that is insensitive to the orientation of atomic dipole. Due to the spontaneous decay, the resonant part of the CP force disappears eventually; however, the decay at the position with maximum force is inhibited. Therefore, during the time evolution, there are special positions (focuses) at which the force is significant for a longer time. Our results show the trap effect that can work on an atom with arbitrary dipole orientation. This provides a method to either trap or reflect an atom in a position far away from surface. © 2014 American Physical Society.