Phys. Rev. Lett. 109, 236806 (2012)

The presence of boundaries leads to measurable manifestations of vacuum fluctuations, such as the attractive Casimir force between two parallel metal plates. This Casimir force could be useful for applications in nano-electromechanical systems, but it is not tunable — or at least not in common materials. Wang-Kong Tse and Allan H. MacDonald predict that things might be different for the Casimir force between two graphene sheets in a strong magnetic field.

Tse and MacDonald studied two parallel graphene sheets that are driven into the quantum Hall regime by a strong perpendicular magnetic field. In this unusual setting, the Casimir energy gains an extra contribution from the Hall current, which results in several unexpected features. When the sheets are separated by large distances, the Casimir force becomes quantized; the force can be either attractive or repulsive depending on the signs of the charge carriers in the two graphene sheets. Moreover, for charge-neutral graphene sheets the Casimir force is strongly suppressed.

These observations, bringing together quantum electrodynamics and Hall physics, hint at the possibility of controlling the Casimir effect.