Casimir-Polder力对左手材料板附近的原子的动力学作用

本文研究了初始处于激发态的两能级原子在左手材料附近运动时Casimir-Polder力对原子动力学的影响. 左手材料有两个的作用: 一是在距离界面波长区域内提供了较强的Casimir-Polder共振力, 二是在这一范围原子的自发辐射受到抑制, 延长了作用时间. 这两种效应使得依靠原子自发辐射这一过程中的Casimir-Polder力能对原子的运动学产生影响, 并将一定初速度的原子排斥远离界面. 由于原子偶极矩的取向会影响Casimir-Polder力的性质, 因此对于某些初始条件(初速度和初始位置), 不同偶极矩取向的原子有不同的运动学结果, 会被吸引到界面或反射出去, 从而对具有不同偶极矩方向的原子进行筛选. 当然由于Casimir-Polder力很小, 能够反射的初速度也很小, 但是已经可以反抗极低温的热涨落, 我们的理论预估值约为15 μupK. 如果和其他约束手段同时作用, 便能对原子的动力学产生更为有利的控制.

Dynamic evolution of an excited atom near the left-handed slab acted by the Casimir-Polder force

Influence of the Casimir-Polder force on a slowly moving atom near a left-handed slab is discussed. We focus on an initially excited atom and its dynamic evolution during the spontaneous decay process. The left-haned slab is adopted based on two factors: (1) It provides a relatively stronger Casimir-Polder force on the excited atom far away from the interface, and (2) it can lead to an inhibited spontaneous decay rate within such a region. Therefore, we can discuss the dynamic evolution of atoms acted only by the Casimir-Polder force. The dynamic evolution discussed here includes both the evolution of atomic population and the atomic displacement. As the Casimir-Polder force depends on the atomic population, while the decay rate is related to the atomic positions, the atomic dynamic evolution is determined by its initial conditions, i.e. its position and volecity. We choose two initial positions for discussion, i.e. (1) the position with the maximum resonant Casimir-Polder force, and (2) the edge of the resonant Casimir-Polder force of the atom with dipole parallel to the interface. Furthermore, we also consider two kinds of orientations of atomic dipole, i. e. parallel and normal to the interface. It is found that the atom can be repulsed away from a surface by the Casimir-Polder force with a proper initial velocity in certain dipole orientaion during the sponatneous decay process. As the atomic dynamics depends on the orientation of the atom dipole momentum, our result can be used as a reference to distinguish atoms with different dipole momenta. Though the force discussed here exists during the spontaneous decay process, it is much different from the recoil force of the atom when it emits a photon during the spontaneous decay. The statistical average of the recoil force is null, but that of the resonant Casimir-Polder force is not. After reasonable estimation, such a Casimir-Polder force can counteract the thermal fluctuation of temperature of 15 μupK during sponatneous decay. If combined with other constraint methods, it is helpful to control the dynamics of an atom more efficiently.