phonon

/foh"non/, n. Physics.

a quantum of sound or vibratory elastic energy, being the analogue of a photon of electromagnetic energy.

[1930-35; PHON- + -ON¹]

* * *

In solid-state physics, a quantum of lattice vibrational energy.

In analogy to a photon (a quantum of light), a phonon is viewed as a wave packet with particlelike properties (see wave-particle duality). The way phonons behave determines or affects various properties of solids. Thermal conductivity, for instance, is explained by phonon interactions. Phonons also provide the basis for understanding superconductivity in certain metals.

* * *

▪ physics

      in solid-state physics, a quantized particle-like unit of vibrational energy arising from the oscillations of the atoms within a crystal. Any solid crystal, such as ordinary table salt ( sodium chloride), consists of atoms bound into a specific repeating three-dimensional spatial pattern called a lattice. Because the atoms have thermal energy, the lattice vibrates in response to applied forces and generates mechanical waves that carry heat and sound through the crystal. In quantum mechanics a packet of these waves constitutes a phonon, which travels within the crystal with particle-like properties. A phonon is a quantum of vibrational mechanical energy, just as a photon is a quantum of light energy.

      In addition to their importance in the thermal and acoustic properties of solids, phonons are essential in the phenomenon of superconductivity—a process in which certain metals such as lead and aluminum lose all of their electrical resistance at temperatures near absolute zero (−273.15 °C; −459.67 °F). Ordinarily, electrons (electron) collide with impurities as they move through a metal, which results in a frictional loss of energy. In superconducting metals at sufficiently low temperatures, however, electrons interact with each other through the intermediate effect of phonons. The result is that the electrons move through the material as a coherent group and no longer lose energy through individual collisions or scatterings. Once this superconducting state has been achieved, any flow of electrical current will persist indefinitely. See also low-temperature phenomena.

* * *