Can an Electrically Neutral Surface Repel Electric Charges?

In a paper just accepted in “Physical Review Letters” Dr. Primoz Rebernik Ribic, member of the lab of Prof. Giorgio Margaritondo (X-Ray Physics Laboratory), show that a charged object moving at high speeds can be repelled by an electrically neutral surface - a result in apparent contrast with textbook electromagnetism. Everyone is familiar with the phenomenon of electrostatic induction. When a balloon is rubbed it will gain negative charge. If placed close to a wall it will stick to it due to an attractive force between the wall and the balloon. This is a consequence of redistribution of charges in the (neutral) wall. The phenomenon, of course, has a microscopic equivalent. A point charge placed outside a solid will always be attracted to its surface, even if the charge moves at relativistic (comparable to the speed of light) speeds parallel to the surface. If, however, the point charge is replaced by a finite-size object, with a width greater than its length, and this object moves in the direction of its length and parallel to the surface, then above a certain speed the object will be repelled by the surface. This counter-intuitive result can, however, be explained with classical electrodynamics. The origin of the repulsion are electromagnetic waves that are excited by the charged object in the solid. The waves produce a recoil, which results in a repulsive force. The result is interesting from the fundamental viewpoint and may also have practical implications in, e.g. accelerator physics.

Primož Rebernik Ribič, Can a metal surface repel electric charges? Phys. Rev. Lett. (2012)

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