Modifying atom-surface interactions with optical fields

Abstract

The ability to control matter on the nanometer scale is greatly influenced by the van der Waals vdW interaction. Therefore, understanding and manipulating the vdW interaction is of interest to the fields of nanotechnology and atom optics. We show that near-resonant light can significantly modify atom-surface vdW interactions in the nonretarded regime. A theory based on quantized electromagnetic fields is used to calculate 1 the ordinary vdW interaction, 2 corrections to the ordinary vdW interaction due to thermal radiation, and 3 modifications to the ordinary vdW interaction that result from monochromatic laser radiation. Near- resonant laser light with an intensity of 5 W /cm 2 is predicted to double the vdW interaction strength for sodium atoms, and possible experiments to detect this effect are discussed. The strength of the van der Waals vdW interaction be- tween matter is usually determined by the atomic or bulk material properties of a system. Therefore, the vdW force can typically only be altered by changing the atomic constituents of the matter involved in the interaction, limiting the ability to control nanometer scale forces. This circumstance reso- nates with the point of view in which the vdW interaction can be thought of as being caused by the fluctuating dipole moment of a quantum-mechanical atom 1. These fluctuat- ing dipoles can then interact with each other, leading to the vdW force between the atoms. However, there exists an al- ternative perspective in which the origin of the vdW interac- tion is due to electromagnetic-field fluctuations in the vacuum, which in turn induce a fluctuating dipole moment in the atoms 2. This suggests that the vdW interaction can be affected by the radiation environment that the matter resides in, opening the exciting possibility of using light to control or even inhibit the vdW interaction. One way to change the radiation environment of matter is through temperature, which exposes the atoms to a thermal electromagnetic field. In principle, this should modify the vdW or Casimir-Polder interaction. Just such an effect has recently been observed for an atom and a nearby surface in the retarded regime 3, where the atom-surface distance z is much larger than the principle transition wavelength of the atom. However, thermal modifications are predicted to be negligible in the nonretarded regime 4,5, where distances are such that z. This is unfortunate since the ability to change the force between atoms and a surface would have an impact on atom chips, atom optics, and quantum reflection experiments.