Phonon
A quantized collective vibrational wave excitation traveling through the periodic atomic or molecular lattice of a solid.
Governing formula
E = (n + ½) ℏ ω, p_crystal = ℏ q
SI unit
eV or J (Phonon Energy)
In depth
Phonons behave as Bosonic quasiparticles carrying quantized vibrational energy and crystal momentum. Acoustic phonons conduct heat and sound in solids, while optical phonons interact strongly with light.
Examples in the real world
Lattice phonons governing thermal conductivity in electrical insulators and mediating electron Cooper pairing in superconductors.