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Short description: Quasiparticles arising from EM wave coupling
Dispersion relation of phonon polaritons in GaP. Red curves are the uncoupled phonon and photon dispersion relations, black curves are the result of coupling (from top to bottom: upper polariton, LO phonon, lower polariton).

In physics, polaritons /pəˈlærɪtɒnz, p-/[1] are quasiparticles resulting from strong coupling of electromagnetic waves with an electric or magnetic dipole-carrying excitation. They are an expression of the common quantum phenomenon known as level repulsion, also known as the avoided crossing principle. Polaritons describe the crossing of the dispersion of light with any interacting resonance. To this extent polaritons can also be thought of as the new normal modes of a given material or structure arising from the strong coupling of the bare modes, which are the photon and the dipolar oscillation. The polariton is a bosonic quasiparticle, and should not be confused with the polaron (a fermionic quasiparticle), which is an electron plus an attached phonon cloud.

Whenever the polariton picture is valid (i.e., when the weak coupling limit is an invalid approximation), the model of photons propagating freely in crystals is insufficient. A major feature of polaritons is a strong dependency of the propagation speed of light through the crystal on the frequency of the photon. For exciton-polaritons, a wealth of experimental results on various aspects have been gained in the case of copper(I) oxide.


Oscillations in ionized gases were observed by Tonks and Langmuir in 1929.[2] Polaritons were first considered theoretically by Tolpygo.[3][4] They were termed light-excitons in Soviet scientific literature. That name was suggested by Pekar, but the term polariton, proposed by Hopfield, was adopted. Coupled states of electromagnetic waves and phonons in ionic crystals and their dispersion relation, now known as phonon polaritons, were obtained by Tolpygo in 1950[3][4] and, independently, by Huang in 1951.[5][6] Collective interactions were published by Pines and Bohm in 1952, and plasmons were described in silver by Fröhlich and Pelzer in 1955. Ritchie predicted surface plasmons in 1957, then Ritchie and Eldridge published experiments and predictions of emitted photons from irradiated metal foils in 1962. Otto first published on surface plasmon-polaritons in 1968.[7] Room-temperature superfluidity of polaritons was observed[8] in 2016 by Giovanni Lerario et al., at CNR NANOTEC Institute of Nanotechnology, using an organic microcavity supporting stable Frenkel exciton-polaritons at room temperature. In February 2018, scientists reported the discovery of a new three-photon form of light, which may involve polaritons, that could be useful in the development of quantum computers.[9][10]


A polariton is the result of the combination of a photon with a polar excitation in a material. The following are types of polaritons:

See also


  1. "Polariton". Polariton. Oxford University Press. 
  2. Tonks, Lewi; Langmuir, Irving (1929-02-01). "Oscillations in Ionized Gases". Physical Review 33 (2): 195–210. doi:10.1103/PhysRev.33.195. Bibcode1929PhRv...33..195T. 
  3. 3.0 3.1 Tolpygo, K.B. (1950). "Physical properties of a rock salt lattice made up of deformable ions". Zhurnal Eksperimentalnoi I Teoreticheskoi Fiziki (J. Exp. Theor. Phys.) 20 (6): 497–509, in Russian. 
  4. 4.0 4.1 K.B. Tolpygo, "Physical properties of a rock salt lattice made up of deformable ions," Zh. Eks.Teor. Fiz. vol. 20, No. 6, pp. 497–509 (1950), English translation: Ukrainian Journal of Physics, vol. 53, special issue (2008); "Archived copy". 
  5. Huang, Kun (1951). "Lattice vibrations and optical waves in ionic crystals". Nature 167 (4254): 779–780. doi:10.1038/167779b0. Bibcode1951Natur.167..779H. 
  6. Huang, Kun (1951). "On the interaction between the radiation field and ionic crystals". Proceedings of the Royal Society of London. A 208 (1094): 352–365. doi:10.1098/rspa.1951.0166. Bibcode1951RSPSA.208..352H. 
  7. Otto, A. (1968). "Excitation of nonradiative surface plasma waves in silver by the method of frustrated total reflection". Z. Phys. 216 (4): 398–410. doi:10.1007/BF01391532. Bibcode1968ZPhy..216..398O. 
  8. Lerario, Giovanni; Fieramosca, Antonio; Barachati, Fábio; Ballarini, Dario; Daskalakis, Konstantinos S.; Dominici, Lorenzo; De Giorgi, Milena; Maier, Stefan A. et al. (2017). "Room-temperature superfluidity in a polariton condensate". Nature Physics 13 (9): 837–841. doi:10.1038/nphys4147. Bibcode2017NatPh..13..837L. 
  9. Hignett, Katherine (16 February 2018). "Physics Creates New Form Of Light That Could Drive The Quantum Computing Revolution". Newsweek. 
  10. Liang, Qi-Yu (16 February 2018). "Observation of three-photon bound states in a quantum nonlinear medium". Science 359 (6377): 783–786. doi:10.1126/science.aao7293. PMID 29449489. Bibcode2018Sci...359..783L. 
  11. Fox, Mark (2010). Optical Properties of Solids (2 ed.). Oxford University Press. p. 107. ISBN 978-0199573370. 
  12. Eradat, N. (2002). "Evidence for braggoriton excitations in opal photonic crystals infiltrated with highly polarizable dyes". Appl. Phys. Lett. 80 (19): 3491. doi:10.1063/1.1479197. Bibcode2002ApPhL..80.3491E. 
  13. Yuen-Zhou, Joel; Saikin, Semion K.; Zhu, Tony; Onbasli, Mehmet C.; Ross, Caroline A.; Bulovic, Vladimir; Baldo, Marc A. (2016-06-09). "Plexciton Dirac points and topological modes" (in en). Nature Communications 7: 11783. doi:10.1038/ncomms11783. ISSN 2041-1723. PMID 27278258. Bibcode2016NatCo...711783Y. 
  14. Kauch, A. (2020). "Generic Optical Excitations of Correlated Systems: pi-tons". Phys. Rev. Lett. 124 (4): 047401. doi:10.1103/PhysRevLett.124.047401. PMID 32058776. Bibcode2020PhRvL.124d7401K. 
  15. Klingshirn, Claus F. (2012-07-06). Semiconductor Optics (4 ed.). Springer. p. 105. ISBN 978-364228362-8. 

Further reading

External links