Plasmons go quantum

摘要

Just as water ripples travel along the surface of a pond after a stone is thrown into it, collective oscillations of conduction electrons called plasmons can be produced in a metal and propagate along its surface. Like pond ripples, plasmons can generally be explained in terms of a classical theory - elec-tromagnetism. But if the metal structure on which they reside is very small (less than about 10nanometres across), quantum-mechanical effects emerge and become relevant, changing the plasmons' oscillation frequency and lifetime. Such changes have so far been poorly understood, particularly on the experimental front.