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A phonon is a collective excitation in a periodic, elastic arrangement of atoms or molecules in condensed matter, specifically in solids and some liquids.A type of quasiparticle in physics, [1] a phonon is an excited state in the quantum mechanical quantization of the modes of vibrations for elastic structures of interacting particles.
The separation between LO and TO phonon frequencies near the Γ-point (small wave vectors) is described by the LST relation. Note this plot shows much higher wavevectors than considered below, and the scale cannot not show the hybridization of the TO branch with light (which would be confined extremely close to Γ).
Phonons take on both labels such that transverse acoustic and optical phonons are denoted TA and TO, respectively; likewise, longitudinal acoustic and optical phonons are denoted LA and LO. The type of surface phonon can be characterized by its dispersion in relation to the bulk phonon modes of the crystal.
A polariton is the result of the combination of a photon with a polar excitation in a material. The following are types of polaritons: Phonon polaritons result from coupling of an infrared photon with an optical phonon
The line shape of the phonon side band is that of a Poisson distribution as it expresses a discrete number of events, electronic transitions with phonons, during a period of time. At higher temperatures, or when the chromophore interacts strongly with the matrix, the probability of multiphonon is high and the phonon side band approximates a ...
In other words, we need to calculate the energies (or frequencies ) of the phonons as a function of their wave vector's k. The relationship between frequency ω and wave vector k is called phonon dispersion. Light and sound are similar in various ways. They both can be thought of in terms of waves, and they both come in quantum mechanical units.
Optical phonons, by contrast, have a non-zero angular frequency at = and have a negative slope, which is also much smaller in magnitude to that of photons. This will result in the crossing of the optical phonon branch and the photon dispersion, leading to their coupling and the forming of a phonon polariton.
Google Dictionary is an online dictionary service of Google that can be accessed with the "define" operator and other similar phrases [note 1] in Google Search. [2] It is also available in Google Translate and as a Google Chrome extension. The dictionary content is licensed from Oxford University Press's Oxford Languages. [3]