 Collective excitation

A collective excitation is a disturbance involving coordinated motion or a coordinated change of many microscopic constituents. It can behave as an effective mode with a well-defined energy and momentum even though no single constituent carries the whole pattern.

A phonon represents a quantized lattice vibration; a magnon represents a spin-wave excitation. Their dispersion and interactions encode material properties. The usefulness of the quasiparticle description depends on whether the excitation persists long enough to have a meaningful mode identity.