CASIMIR EFFECTS

This subsection of our group is concerned with the investigation of quantum electrodynamical phenomena such as the Casimir effect, which is an attractive force between uncharged parallel metallic plates. This effect is a manifestation of quantum mechanical vacuum fluctuations, i.e. the zero-point energy of the electromagnetic field, and can be altered by changing the boundary conditions imposed on these fields. This engineering of vacuum fluctuations can be used to modify the Casimir force for specific applications and could lead to new phenomena, e.g. QED torques, repulsive vacuum forces, and others.

Graduate students: Jeremy N. Munday and Mark B. Romanowsky
Undergraduates: Limor Spector

QED torque

The boundary conditions imposed on the fluctuating electromagnetic fields modify the zero point energy of the vacuum. If the boundary conditions have an angular dependence (e.g. for birefringent materials), the zero point energy will also have an angular dependence. Therefore, there should exist a QED torque which will cause one birefringent plate to rotate with respect to a second nearby plate in order to minimize its energy. We are currently exploring this phenomenon experimentally.

Casimir force with superconductors

High-temperature cuprate superconductors are the subject of very intense research effort, with a large number of properties that are not yet well understood. We are exploring how these materials influence the Casimir force in their normal and superconducting states, with an eye to how these measurements may provide information about the cuprate superconductors that is not provided easily by other methods.

In collaboration with Richard Schalek (Harvard University), and Genda Gu and Qiang Li (Brookhaven National Laboratory).

Repulsive QED forces

Many studies in recent years have explored the Casimir force to high precision between metallic surfaces. We are also exploring the more general case, developed by E.M. Lifshitz, which describes the QED fluctuations between materials of arbitrary (but isotropic) dielectric properties. This leads to both attractive and repulsive QED forces.

Mems technology and the Casimir force

Our first studies of the Casimir force were done using Micro-Electro-Mechanical Systems (MEMS). Since then, we have shown that the Casimir force can be incorporated into the design of MEMS and used for their actuation. We have also used these devices to study the effect of the skin depth of thin films on the Casimir force, and how hydrogen switchable mirrors (materials whose reflectivity depends on hydrogen concentration of the atmosphere) modify the Casimir force.