When in Surface Science the interface between a solid and the vacuum is studied, attention is typically focussed on the properties of the first. We argument, that the properties of the vacuum need to be considered too!
The quantum mechanical nature of (empty) space has far-reaching consequences in many branches of physics, ranging from (sub-)atomic physics to cosmology. In particular, the existence of electromagnetic vacuum fluctuations manifests itself most impressively in the Casimir force, a stochastic and feeble force, so hard to measure properly, that it was considered to be solely of academic interest for a long time. With the current revolution in nano-technology, however, there is a rising, yet even economic need for a quantitative understanding of this QED effect.
I will present an experiment, in which the Casimir-Polder force between a single atom and the surface of a solid is determined quantitatively to the percent level. It is based on the Atomic Beam Spin Echo method developed in Heidelberg, an atom interferometry method, in which we combine the exclusive surface sensitivity of thermal atom scattering with the resolution of in-beam magnetic resonance techniques. This technique will be introduced and its high resolving power (down to sub-neV) shown in some simple scattering experiments.
Utilizing quantum reflection as a tool, which depends very sensitively on the long range details of the attractive atom-surface interaction, we have been able to clearly identify the Casimir and the van der Waals branches for a variety of surfaces. Finally, I will show on-going measurements focussing on the dependency of the working of the vacuum fluctuations on temperature, geometry and spectral properties of the solid. Our data for example show that the Casimir interaction can be significantly altered by heating the surface. In particular in view of nano-technology, I will discuss how we may put the quantum field to use by specifically modifying the interaction via the topology of surfaces. Our latest data show a significant change in the Casimir force, when using nano-structured substrates instead of flat ones. |