Polariton

{{Short description|Quasiparticles arising from EM wave coupling}} {{Distinguish|Polaron}} {{too technical|date=April 2018}} [[Image:Phonon polaritons.svg|thumb|270px|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).]] {{Condensed matter physics}} In physics, '''polaritons''' {{IPAc-en|p|ə|ˈ|l|ær|ᵻ|t|ɒ|n|z|,_|p|oʊ|-}}{{refn|{{Cite dictionary |url=http://www.lexico.com/definition/Polariton |archive-url=https://web.archive.org/web/20210117083254/https://www.lexico.com/definition/polariton |url-status=dead |archive-date=2021-01-17 |title=Polariton |dictionary=Lexico UK English Dictionary |publisher=Oxford University Press}} }} are bosonic quasiparticles resulting from strong coupling of electromagnetic waves (photon) with an electric or magnetic dipole-carrying excitation (state) of solid or liquid matter (such as a phonon, plasmon, or an exciton).{{example needed|date=April 2018}} Polaritons describe the crossing of the dispersion of light with any interacting resonance.

They are an expression of level repulsion (quantum phenomenon), also known as the avoided crossing principle. To this extent polaritons can 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. Bosonic quasiparticles are distinct from polarons (fermionic quasiparticle), which is an electron plus an attached phonon cloud.

Polaritons violate the weak coupling limit and the associated photons do not propagate freely in crystals. Instead, propagation speed depends strongly on the frequency of the photon.

Significant experimental results on various aspects of exciton-polaritons have been gained in the case of copper(I) oxide.

== History == Oscillations in ionized gases were observed by Lewi Tonks and Irving Langmuir in 1929.<ref>{{Cite journal|last1=Tonks|first1=Lewi|last2=Langmuir|first2=Irving|date=1929-02-01|title=Oscillations in Ionized Gases|journal=Physical Review|volume=33|issue=2|pages=195–210|doi=10.1103/PhysRev.33.195|pmid=16587379 |bibcode=1929PhRv...33..195T|pmc=1085653}}</ref> Polaritons were first considered theoretically by Kirill Borisovich Tolpygo.<ref name=":1" /><ref name=":0">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); {{cite web |url=http://ujp.bitp.kiev.ua/files/journals/53/si/53SI21p.pdf |title=Archived copy |access-date=2015-10-15 |url-status=dead |archive-url=https://web.archive.org/web/20151208052530/http://ujp.bitp.kiev.ua/files/journals/53/si/53SI21p.pdf |archive-date=2015-12-08 }}</ref> They were termed light-excitons in Soviet scientific literature. That name was suggested by Solomon Isaakovich Pekar, but the term ''polariton,'' proposed by John 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 Kirill Tolpygo in 1950<ref name=":1">{{Cite journal|title = Physical properties of a rock salt lattice made up of deformable ions|last = Tolpygo|first = K.B.|date = 1950|journal = Zhurnal Eksperimentalnoi I Teoreticheskoi Fiziki (J. Exp. Theor. Phys.)|volume = 20|issue = 6|pages = 497–509, in Russian}}</ref><ref name=":0" /> and independently by Huang Kun in 1951.<ref>{{Cite journal|title = Lattice vibrations and optical waves in ionic crystals|last = Huang|first = Kun|date = 1951|journal = Nature|doi = 10.1038/167779b0|volume = 167|issue = 4254|pages = 779–780|bibcode = 1951Natur.167..779H |s2cid = 30926099}}</ref><ref>{{Cite journal|title = On the interaction between the radiation field and ionic crystals|last = Huang|first = Kun|date = 1951|journal = Proceedings of the Royal Society of London|doi = 10.1098/rspa.1951.0166|volume = 208|issue = 1094|pages = 352–365|bibcode = 1951RSPSA.208..352H|s2cid = 97746500}}</ref> Collective interactions were published by David Pines and David Bohm in 1952, and plasmons were described in silver by Herbert Fröhlich and H. Pelzer in 1955.

R.H. Ritchie predicted surface plasmons in 1957, then Ritchie and H.B. Eldridge published experiments and predictions of emitted photons from irradiated metal foils in 1962. Otto first published on surface plasmon-polaritons in 1968.<ref>{{Cite journal|title = Excitation of nonradiative surface plasma waves in silver by the method of frustrated total reflection|last = Otto|first = A.|date = 1968|journal = Z. Phys.|doi = 10.1007/BF01391532|volume = 216|issue = 4|pages = 398–410|bibcode = 1968ZPhy..216..398O |s2cid = 119934323}}</ref> Room-temperature superfluidity of polaritons was observed 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.<ref>{{Cite journal|title = Room-temperature superfluidity in a polariton condensate|last1 = Lerario|first1 = Giovanni|first2 = Antonio|last2 = Fieramosca|first3 = Fábio|last3 = Barachati|first4 = Dario|last4 = Ballarini|first5 = Konstantinos S.|last5 = Daskalakis|first6 = Lorenzo|last6 = Dominici|first7 = Milena|last7 = De Giorgi|first8 = Stefan A.|last8 = Maier|first9 = Giuseppe|last9 = Gigli|first10 = Stéphane|last10 = Kéna-Cohen|first11 = Daniele|last11 = Sanvitto|year = 2017|journal = Nature Physics|doi = 10.1038/nphys4147|volume =13|issue = 9|pages = 837–841|bibcode =2017NatPh..13..837L |arxiv = 1609.03153|s2cid = 119298251}}</ref>

In 2018, scientists reported the discovery of a new three-photon form of light, which may involve polaritons and could be useful in quantum computers.<ref name="NW-20180216">{{cite web |last=Hignett |first=Katherine |title=Physics Creates New Form Of Light That Could Drive The Quantum Computing Revolution |url=http://www.newsweek.com/photons-light-physics-808862 |date=16 February 2018 |work=Newsweek |access-date=17 February 2018 }}</ref><ref name="SCI-20180216">{{cite journal |author=Liang, Qi-Yu|display-authors=etal|title=Observation of three-photon bound states in a quantum nonlinear medium |date=16 February 2018 |journal=Science |volume=359 |issue=6377 |pages=783–786 |doi=10.1126/science.aao7293 |arxiv=1709.01478 |bibcode=2018Sci...359..783L |pmid=29449489 |pmc=6467536 }}</ref>

In 2024 researchers reported ultrastrong coupling of the PEPI layer in a Fabry-Pérot microcavity consisting of two partially reflective mirrors. The PEPI layer is a two-dimensional perovskite made of (PEA)2PbI4 (phenethylammonium lead iodide). Placing a PEPI layer within a Fabry-Pérot microcavity forms polaritons and allows control of exciton-exciton annihilation, increasing solar cell efficiency and ED intensity.<ref>{{Cite web |last=Daugherty |first=Justin |date=2024-08-09 |title=Stronger Together: Coupling Excitons to Polaritons for Better Solar Cells & Higher Intensity LEDs |url=https://cleantechnica.com/2024/08/08/stronger-together-coupling-excitons-to-polaritons-for-better-solar-cells-higher-intensity-leds/ |access-date=2024-10-12 |website=CleanTechnica |publisher=US Department of Energy National Renewable Energy Laboratory |language=en-US}}</ref>

==Types== 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 * Exciton polaritons result from coupling of visible light with an exciton<ref> {{cite book |last=Fox |first=Mark |page=107 |date=2010 |title=Optical Properties of Solids |edition=2 |url=https://global.oup.com/academic/product/optical-properties-of-solids-9780199573370?lang=en&cc=no |publisher=Oxford University Press |isbn=978-0199573370 }} </ref> * Intersubband polaritons result from coupling of an infrared or terahertz photon with an intersubband excitation * Surface plasmon polaritons result from coupling of surface plasmons with light (the wavelength depends on the substance and its geometry) * Bragg polaritons ("Braggoritons") result from coupling of Bragg photon modes with bulk excitons<ref name="eradat">{{cite journal | last1 = Eradat | first1 = N. | display-authors = etal | year = 2002 | title = Evidence for braggoriton excitations in opal photonic crystals infiltrated with highly polarizable dyes | journal = Appl. Phys. Lett. | volume = 80 | issue = 19| page = 3491 | doi=10.1063/1.1479197| arxiv = cond-mat/0105205 | bibcode = 2002ApPhL..80.3491E | s2cid = 119077076 }}</ref> * Plexcitons result from coupling plasmons with excitons<ref>{{Cite journal|last1=Yuen-Zhou|first1=Joel|last2=Saikin|first2=Semion K.|last3=Zhu|first3=Tony|last4=Onbasli|first4=Mehmet C.|last5=Ross|first5=Caroline A.|last6=Bulovic|first6=Vladimir|last7=Baldo|first7=Marc A.|date=2016-06-09|title=Plexciton Dirac points and topological modes|journal=Nature Communications|language=en|volume=7|article-number=11783|doi=10.1038/ncomms11783|issn=2041-1723|pmc=4906226|pmid=27278258|arxiv=1509.03687|bibcode=2016NatCo...711783Y}}</ref> * Magnon polaritons result from coupling of magnon with light * Pi-tons result from coupling of alternating charge or spin fluctuations with light, distinctly different from magnon or exciton polaritons<ref name="kauch">{{cite journal | last1 = Kauch | first1 = A. | display-authors = etal | year = 2020 | title = Generic Optical Excitations of Correlated Systems: pi-tons| journal = Phys. Rev. Lett. | volume = 124 | issue = 4| article-number = 047401 | doi=10.1103/PhysRevLett.124.047401 | pmid = 32058776 | arxiv = 1902.09342 | bibcode = 2020PhRvL.124d7401K | s2cid = 119215630 }}</ref> * Cavity polaritons<ref> {{cite book |last= Klingshirn |first=Claus F. |date= 2012-07-06|title=Semiconductor Optics |edition=4 |url=https://www.springer.com/us/book/9783642283611 |publisher=Springer |page=105 |isbn=978-364228362-8 }} </ref>

== References == {{Reflist|2}}

==Further reading== *{{cite journal|title=The Interaction of Radio-Frequency Fields With Dielectric Materials at Macroscopic to Mesoscopic Scales|first=J.|last=Baker-Jarvis|journal=Journal of Research of the National Institute of Standards and Technology|volume=117|publisher=National Institute of Science and Technology|year=2012|pages=1–60|doi=10.6028/jres.117.001|pmc=4553869|pmid=26900513|author-link1=James Baker-Jarvis}} *{{cite journal |last=Fano |first=U. |year=1956 |title=Atomic Theory of Electromagnetic Interactions in Dense Materials |journal=Physical Review |volume=103 |issue=5 |pages=1202–1218 |doi=10.1103/PhysRev.103.1202 |bibcode = 1956PhRv..103.1202F }} *{{cite journal |last=Hopfield |first=J. J. |year=1958 |title=Theory of the Contribution of Excitons to the Complex Dielectric Constant of Crystals |journal=Physical Review |volume=112 |issue=5 |pages=1555–1567 |doi=10.1103/PhysRev.112.1555 |bibcode = 1958PhRv..112.1555H }} *{{cite news|title=New type of supercomputer could be based on 'magic dust' combination of light and matter |url=http://www.cam.ac.uk/research/news/new-type-of-supercomputer-could-be-based-on-magic-dust-combination-of-light-and-matter|access-date=28 September 2017|publisher=University of Cambridge|date=25 September 2017|language=en}}

==External links== * [https://www.youtube.com/watch?v=sWmvZ0IGrsU YouTube animation explaining what is polariton in a semiconductor micro-resonator.] * [https://polaritonics.nanotec.cnr.it/ Description of the experimental research on polariton fluids at the Institute of Nanotechnologies.]

Category:Quasiparticles *