polariton superfluid

Polariton superfluid is predicted to be a state of the exciton-polaritons system that combines the characteristics of lasers with those of excellent electrical conductors.

{{Cite journal|title = Exciton–polariton condensates|year = 2014|journal = Nature Physics|doi = 10.1038/nphys3143|arxiv = 1411.6822 |bibcode = 2014NatPh..10..803B |volume=10 |issue = 11|pages=803–813|vauthors=Byrnes T, Kim NY, Yamamoto Y |title-link = Bose-Einstein condensation of polaritons|s2cid = 118545281}}

{{cite journal|title = The road towards polaritonic devices |year = 2016|journal=Nature Materials|doi = 10.1038/nmat4668|volume=15|issue=10|pages=1061–1073|pmid=27429208|vauthors=Sanvitto D, Kéna-Cohen S |bibcode=2016NatMa..15.1061S}}

Researchers look for this state in a solid state optical microcavity coupled with quantum well excitons. The idea is to create an ensemble of particles known as exciton-polaritons and trap them.

{{Cite journal

| author = R. Balili

| display-authors = etal

| date = 2007

| title = Bose-Einstein Condensation of Microcavity Polaritons in a Trap

| journal = Science

| volume = 316 | issue = 5827

| pages = 1007–10

| doi = 10.1126/science.1140990

| pmid = 17510360

| bibcode = 2007Sci...316.1007B| s2cid = 2682022

}}

Wave behavior in this state results in a light beam similar to that from a laser but possibly more energy efficient.

Unlike traditional superfluids that need temperatures of approximately ~4 K, the polariton superfluid could in principle be stable at much higher temperatures, and might soon be demonstrable at room temperature.{{Cite web

|author=Morgan Kelly

|title=Pitt Researchers Create New Form of Matter

|url=http://mac10.umc.pitt.edu/m/FMPro?-db=ma&-lay=a&-format=d.html&id=2936&-Find

|publisher=University of Pittsburgh

|access-date=2007-05-31

|archive-url=https://web.archive.org/web/20070525033906/http://mac10.umc.pitt.edu/m/FMPro?-db=ma&-lay=a&-format=d.html&id=2936&-Find

|archive-date=2007-05-25

|url-status=dead

}} Evidence for polariton superfluidity was reported in by Alberto Amo and coworkers,{{cite journal | last1=Amo | first1=Alberto | last2=Lefrère | first2=Jérôme | last3=Pigeon | first3=Simon | last4=Adrados | first4=Claire | last5=Ciuti | first5=Cristiano | last6=Carusotto | first6=Iacopo | last7=Houdré | first7=Romuald | last8=Giacobino | first8=Elisabeth | last9=Bramati | first9=Alberto |display-authors=5| title=Superfluidity of polaritons in semiconductor microcavities | journal=Nature Physics | volume=5 | issue=11 | date=2009-09-20 | issn=1745-2473 | doi=10.1038/nphys1364 | pages=805–810| arxiv=0812.2748 | bibcode=2009NatPh...5..805A | doi-access=free }} based on the suppressed scattering of the polaritons during their motion.

Although several other researchers are working in the same field,

{{cite web

| author = Jacek Kasprzak

| year = 2006

| title = Condensation of exciton polaritons

| url = http://tel.archives-ouvertes.fr/docs/00/11/83/16/PDF/Kasprzak_Jacek.pdf

| publisher = Université Joseph Fourier - Grenoble I

}}{{cite web

| author = Hui Deng

| title = Dynamic Condensation of Semiconductor Microcavity Polaritons

| url = http://www.stanford.edu/group/yamamotogroup/Thesis/HDthesis.pdf

| publisher = Stanford University

| year = 2006

| access-date = 2007-10-15

| archive-date = 2007-03-08

| archive-url = https://web.archive.org/web/20070308042141/http://www.stanford.edu/group/yamamotogroup/Thesis/HDthesis.pdf

| url-status = dead

}} the terminology and conclusions are not completely shared by the different groups. In particular, important properties of superfluids, such as zero viscosity, and of lasers, such as perfect optical coherence, are a matter of debate.

{{Cite journal |title=Superflow of resonantly driven polaritons against a defect |author1=Cancellieri, E.|author2=Marchetti, F. M.| author3=Szymańska, M. H.|author4=Tejedor, C. |journal=Phys. Rev. B |volume=82 |issue=224512 |pages=224512 |year=2010 |doi=10.1103/PhysRevB.82.224512 |arxiv=1009.3120 |bibcode=2010PhRvB..82v4512C|s2cid=118458289}}

{{Cite journal |title=Beyond superfluidity in non-equilibrium Bose–Einstein condensates |author1=Pinsker, F. |journal=New Journal of Physics |volume=19 |issue=113046 |pages=113046 |year=2017 |doi=10.1088/1367-2630/aa9561 |arxiv=1611.03430 |bibcode=2017NJPh...19k3046P |s2cid=119076087 }}

Although, there is clear indication of quantized vortices when the pump beam has orbital angular momentum.

{{Cite journal

| author = D. Sanvitto

| display-authors = etal

| date = 2010

| title = Persistent currents and quantized vortices in a polariton superfluid

| journal = Nature Physics

| volume = 6 | issue = 7 | pages = 527–533

| doi = 10.1038/nphys1668

|bibcode = 2010NatPh...6..527S |arxiv = 0907.2371 | s2cid = 119278255

}}

Furthermore, clear evidence has been demonstrated also for superfluid motion of polaritons, in terms of the Landau criterion and the suppression of scattering from defects when the flow velocity is slower than the speed of sound in the fluid.

{{Cite journal

| author = A. Amo

| display-authors = etal

| date = 2009

| title = Superfluidity of polaritons in semiconductor microcavities

| journal = Nature Physics

| volume = 5 | issue = 11

| pages = 805–810

| doi = 10.1038/nphys1364

| arxiv = 0812.2748

| bibcode = 2009NatPh...5..805A

| s2cid = 56339602

}}

The same phenomena have been demonstrated in an organic exciton polariton fluid, representing the first achievement of room-temperature superfluidity of a hybrid fluid of photons and excitons.

{{Cite journal

| author = G. Lerario

| display-authors = etal

| date = 2017

| title = Room-temperature superfluidity in a polariton condensate

| journal = Nature Physics

| volume = online ed. | issue = 9

| pages = 837–841

| doi = 10.1038/nphys4147

| arxiv = 1609.03153| bibcode = 2017NatPh..13..837L| s2cid = 119298251

}}