This article has multiple issues. Please help improve it or discuss these issues on the talk page. (Learn how and when to remove these template messages)

Excitonpolariton is a type of polariton; a hybrid light and matter quasiparticle arising from the strong coupling of the electromagnetic dipolar oscillations of excitons (either in bulk or quantum wells) and photons.^{[1]}
Theory
The coupling of the two oscillators, photons modes in the semiconductor optical microcavity and excitons of the quantum wells, results in the energy anticrossing of the bare oscillators, giving rise to the two new normal modes for the system, known as the upper and lower polariton resonances (or branches). The energy shift is proportional to the coupling strength (dependent, e.g., on the field and polarization overlaps). The higher energy or upper mode (UPB, upper polariton branch) is characterized by the photonic and exciton fields oscillating inphase, while the LPB (lower polariton branch) mode is characterized by them oscillating with phaseopposition. Microcavity excitonpolaritons inherit some properties from both of their roots, such as a light effective mass (from the photons) and a capacity to interact with each other (from the strong exciton nonlinearities) and with the environment (including the internal phonons, which provide thermalization, and the outcoupling by radiative losses). In most cases the interactions are repulsive, at least between polariton quasiparticles of the same spin type (intraspin interactions) and the nonlinearity term is positive (increase of total energy, or blueshift, upon increasing density).^{[2]}
Recently, researchers measured the longrange transport in organic materials coupled to optical microcavities and showed that excitonpolaritons propagate over several microns.^{[3]}
Other features
Polaritons are also characterized by nonparabolic energymomentum dispersion relations, which limit the validity of the parabolic effectivemass approximation to a small range of momenta .^{[4]} They also have a spin degreeoffreedom, making them spinorial fluids able to sustain different polarization textures. Excitonpolaritons are composite bosons which can be observed to form BoseEinstein condensates,^{[5]}^{[6]}^{[7]}^{[8]} and sustain polariton superfluidity and quantum vortices^{[9]} and are prospected for emerging technological applications.^{[10]} Many experimental works currently focus on polariton lasers,^{[11]} optically addressed transistors,^{[12]} nonlinear states such as solitons and shock waves, longrange coherence properties and phase transitions, quantum vortices and spinorial patterns. Modelization of excitonpolariton fluids mainly rely on the use of GPE (Gross–Pitaevskii equations) which are in the form of nonlinear Schrödinger equations.^{[13]}
See also
 Polariton
 Polariton superfluid
 BoseEinstein condensation of polaritons
 BoseEinstein condensation of quasiparticles
References
 ^ S.I. Pekar (1958). "Theory of electromagnetic waves in a crystal with excitons". Journal of Physics and Chemistry of Solids. 5 (1–2): 11–22. Bibcode:1958JPCS....5...11P. doi:10.1016/00223697(58)901276.
 ^ Vladimirova, M; et al. (2010). "Polaritonpolariton interaction constants in microcavities". Physical Review B. 82 (7): 075301. Bibcode:2010PhRvB..82g5301V. doi:10.1103/PhysRevB.82.075301.
 ^ Georgi Gary Rozenman; Katherine Akulov; Adina Golombek; Tal Schwartz (2018). "LongRange Transport of Organic ExcitonPolaritons Revealed by Ultrafast Microscopy". ACS Photonics. 5 (1): 105–110. doi:10.1021/acsphotonics.7b01332.
 ^ Pinsker, F.; Ruan, X.; Alexander, T. (2017). "Effects of the nonparabolic kinetic energy on nonequilibrium polariton condensates". Scientific Reports. 7 (1891): 1891. arXiv:1606.02130. Bibcode:2017NatSR...7.1891P. doi:10.1038/s41598017011138. PMC 5432531. PMID 28507290.
 ^ Deng, H (2002). "Condensation of semiconductor microcavity exciton polaritons". Science. 298 (5591): 199–202. Bibcode:2002Sci...298..199D. doi:10.1126/science.1074464. PMID 12364801. S2CID 21366048.
 ^ Kasprzak, J (2006). "Bose–Einstein condensation of exciton polaritons". Nature. 443 (7110): 409–14. Bibcode:2006Natur.443..409K. doi:10.1038/nature05131. PMID 17006506.
 ^ Deng, H (2010). "Excitonpolariton BoseEinstein condensation". Reviews of Modern Physics. 82 (2): 1489–1537. Bibcode:2010RvMP...82.1489D. doi:10.1103/RevModPhys.82.1489. S2CID 122733835.
 ^ Byrnes, T.; Kim, N. Y.; Yamamoto, Y. (2014). "Exciton–polariton condensates". Nature Physics. 10 (11): 803. arXiv:1411.6822. Bibcode:2014NatPh..10..803B. doi:10.1038/nphys3143.
 ^ Dominici, L; Dagvadorj, G; Fellows, JM; et al. (2015). "Vortex and halfvortex dynamics in a nonlinear spinor quantum fluid" (PDF). Science Advances. 1 (11): e1500807. arXiv:1403.0487. Bibcode:2015SciA....1E0807D. doi:10.1126/sciadv.1500807. PMC 4672757. PMID 26665174.
 ^ Sanvitto, D.; KénaCohen, S. (2016). "The road towards polaritonic devices". Nature Materials. 15 (10): 1061–73. Bibcode:2016NatMa..15.1061S. doi:10.1038/nmat4668. PMID 27429208.
 ^ Schneider, C.; RahimiIman, A.; Kim, N. Y.; et al. (2013). "An electrically pumped polariton laser". Nature. 497 (7449): 348–352. Bibcode:2013Natur.497..348S. doi:10.1038/nature12036. PMID 23676752.
 ^ Ballarini, D.; De Giorgi, M.; Cancellieri, E.; et al. (2013). "Alloptical polariton transistor". Nature Communications. 4 (2013): 1778. arXiv:1201.4071. Bibcode:2013NatCo...4E1778B. doi:10.1038/ncomms2734. PMID 23653190.
 ^ Moxley, Frederick Ira; Byrnes, Tim; Ma, Baoling; Yan, Yun; Dai, Weizhong (2015). "A GFDTD scheme for solving multidimensional open dissipative Gross–Pitaevskii equations". Journal of Computational Physics. 282: 303–316. Bibcode:2015JCoPh.282..303M. doi:10.1016/j.jcp.2014.11.021. ISSN 00219991.