ABSTRACT
Generally speaking, a plasmon is a quantum of a plasma oscillation,
namely, a fast oscillation of a free electron cloud (or gas) in a
conducting medium. Metals are the most common materials that
can sustain plasmons; in fact, they can be seen as a plasma of
positive ions (i.e., the nuclei and the core electrons) dressed by free
electrons in the conduction band (gas or cloud of free electrons).
Two categories of plasmons can be individuated: volume plasmon (see Section 7.1.1) and surface plasmon.
