Polariton

In physics, polaritons /pəˈlærɪtɒnz, poʊ-/[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 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 one), which is an electron plus an attached phonon cloud.

Not to be confused with Polaron.
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).

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, rich experimental results on various aspects have been gained in copper(I) oxide.

History

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]

Types

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

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See also

References
  1. "Polariton". Oxford Dictionaries UK Dictionary. Oxford University Press. Retrieved 2016-01-21.
  2. Tonks, Lewi; Langmuir, Irving (1929-02-01). "Oscillations in Ionized Gases". Physical Review. 33 (2): 195–210. Bibcode:1929PhRv...33..195T. doi:10.1103/PhysRev.33.195.
  3. 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. 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" (PDF). Archived from the original (PDF) on 2015-12-08. Retrieved 2015-10-15.CS1 maint: archived copy as title (link)
  5. Huang, Kun (1951). "Lattice vibrations and optical waves in ionic crystals". Nature. 167 (4254): 779–780. Bibcode:1951Natur.167..779H. doi:10.1038/167779b0.
  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.
  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. Bibcode:1968ZPhy..216..398O. doi:10.1007/BF01391532.
  8. Lerario, Giovanni; Fieramosca, Antonio; Barachati, Fábio; Ballarini, Dario; Daskalakis, Konstantinos S.; Dominici, Lorenzo; De Giorgi, Milena; Maier, Stefan A.; Gigli, Giuseppe; Kéna-Cohen, Stéphane; Sanvitto, Daniele (2017). "Room-temperature superfluidity in a polariton condensate". Nature Physics. 13 (9): 837–841. arXiv:1609.03153. Bibcode:2017NatPh..13..837L. doi:10.1038/nphys4147.
  9. Hignett, Katherine (16 February 2018). "Physics Creates New Form Of Light That Could Drive The Quantum Computing Revolution". Newsweek. Retrieved 17 February 2018.
  10. Liang, Qi-Yu; et al. (16 February 2018). "Observation of three-photon bound states in a quantum nonlinear medium". Science. 359 (6377): 783–786. arXiv:1709.01478. Bibcode:2018Sci...359..783L. doi:10.1126/science.aao7293. PMC 6467536. PMID 29449489.
  11. Fox, Mark (2010). Optical Properties of Solids (2 ed.). Oxford University Press. p. 107. ISBN 978-0199573370.
  12. Eradat, N.; et al. (2002). "Evidence for braggoriton excitations in opal photonic crystals infiltrated with highly polarizable dyes". Appl. Phys. Lett. 80 (19): 3491. arXiv:cond-mat/0105205. doi:10.1063/1.1479197.
  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". Nature Communications. 7: 11783. arXiv:1509.03687. Bibcode:2016NatCo...711783Y. doi:10.1038/ncomms11783. ISSN 2041-1723. PMC 4906226. PMID 27278258.
  14. Klingshirn, Claus F. (2012-07-06). Semiconductor Optics (4 ed.). Springer. p. 105. ISBN 978-364228362-8.

Further reading
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