Elementary excitation in the quantum mechanical treatment of vibrations in a crystal lattice. An energy bundle that behaves as a particle of energy hν, with ν the vibration frequency and h the Planck constant.
  1. A phonon can be considered as an acoustic @M03958@ of thermal vibration of a crystal lattice (or liquid helium II).
  2. Every harmonic vibration can be decomposed in phonons, which are the elementary vibrations. The total number of phonons in a system that has internal vibrations (e.g., a crystal) is related to the temperature of the system.
  3. The concept of phonons provides a simplification in the theories of thermal and electrical conduction in solids.
  4. For example, interactions between phonons and electrons are thought to be responsible for such phenomena as 'superconductivity'.
PAC, 2007, 79, 293. 'Glossary of terms used in photochemistry, 3rd edition (IUPAC Recommendations 2006)' on page 382 (