physics Physics is the natural science that studies matter, its fundamental constituents, its motion and behavior through space and time, and the related entities of energy and force. "Physical science is that department of knowledge which r ...

, polaritons are

quasiparticle In physics, quasiparticles and collective excitations are closely related emergent phenomena arising when a microscopically complicated system such as a solid behaves as if it contained different weakly interacting particles in vacuum. For exam ...

s resulting from strong coupling of

electromagnetic wave In physics, electromagnetic radiation (EMR) consists of waves of the electromagnetic (EM) field, which propagate through space and carry momentum and electromagnetic radiant energy. It includes radio waves, microwaves, infrared, (visib ...

s with an electric or magnetic

dipole In physics, a dipole () is an electromagnetic phenomenon which occurs in two ways: *An electric dipole deals with the separation of the positive and negative electric charges found in any electromagnetic system. A simple example of this system i ...

-carrying excitation. They are an expression of the common

quantum In physics, a quantum (plural quanta) is the minimum amount of any physical entity (physical property) involved in an interaction. The fundamental notion that a physical property can be "quantized" is referred to as "the hypothesis of quantizati ...

phenomenon known as

level repulsion Level repulsion is the quantum mechanical Quantum mechanics is a fundamental theory in physics that provides a description of the physical properties of nature at the scale of atoms and subatomic particles. It is the foundation of all quantu ...

, also known as the avoided crossing principle. Polaritons describe the crossing of the

dispersion Dispersion may refer to: Economics and finance *Dispersion (finance), a measure for the statistical distribution of portfolio returns *Price dispersion, a variation in prices across sellers of the same item *Wage dispersion, the amount of variatio ...

of light with any interacting

resonance Resonance describes the phenomenon of increased amplitude that occurs when the frequency of an applied periodic force (or a Fourier component of it) is equal or close to a natural frequency of the system on which it acts. When an oscillatin ...

. To this extent polaritons can also be thought of as the new

normal modes A normal mode of a dynamical system is a pattern of motion in which all parts of the system move sinusoidally with the same frequency and with a fixed phase relation. The free motion described by the normal modes takes place at fixed frequencies. ...

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

boson In particle physics, a boson ( ) is a subatomic particle whose spin quantum number has an integer value (0,1,2 ...). Bosons form one of the two fundamental classes of subatomic particle, the other being fermions, which have odd half-integer s ...

ic quasiparticle, and should not be confused with the

polaron A polaron is a quasiparticle used in condensed matter physics to understand the interactions between electrons and atoms in a solid material. The polaron concept was proposed by Lev Landau in 1933 and Solomon Pekar in 1946 to describe an electro ...

fermion In particle physics, a fermion is a particle that follows Fermi–Dirac statistics. Generally, it has a half-odd-integer spin: spin , spin , etc. In addition, these particles obey the Pauli exclusion principle. Fermions include all quarks an ...

ic quasiparticle), which is an electron plus an attached

phonon In physics, a phonon is a collective excitation in a periodic, Elasticity (physics), elastic arrangement of atoms or molecules in condensed matter physics, condensed matter, specifically in solids and some liquids. A type of quasiparticle, a phon ...

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 Frequency is the number of occurrences of a repeating event per unit of time. It is also occasionally referred to as ''temporal frequency'' for clarity, and is distinct from ''angular frequency''. Frequency is measured in hertz (Hz) which is eq ...

of the photon. For exciton-polaritons, a wealth of experimental results on various aspects have been gained in the case of

copper(I) oxide Copper(I) oxide or cuprous oxide is the inorganic compound with the formula Cu2O. It is one of the principal oxides of copper, the other being or copper(II) oxide or cupric oxide (CuO). This red-coloured solid is a component of some antifoulin ...

History

Oscillations in ionized gases were observed by

Lewi Tonks Lewi Tonks (1897–1971) was an American quantum physicist noted for his discovery (with Marvin D. Girardeau) of the Tonks–Girardeau gas. Tonks was employed by General Electric for most of his working life, researching microwaves and ferromagne ...

and

Irving Langmuir Irving Langmuir (; January 31, 1881 – August 16, 1957) was an American chemist, physicist, and engineer. He was awarded the Nobel Prize in Chemistry in 1932 for his work in surface chemistry. Langmuir's most famous publication is the 1919 art ...

in 1929. Polaritons were first considered theoretically by

Kirill Borisovich Tolpygo Kirill Borisovich Tolpygo ( uk, Кирилo Борисович Толпиго; russian: Кирилл Борисович Толпыго; 3 May 1916 – 13 May 1994) was a Soviet physicist and a corresponding member of the National Academy of Scienc ...

.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); They were termed light-excitons in Soviet scientific literature. That name was suggested by

Solomon Isaakovich Pekar Solomon Isaakovich Pekar ( uk, Соломон Ісаакович Пекар; russian: Соломон Исаакович Пекар; 16 March 1917 – 8 July 1985) was a Soviet theoretical physicist, born in Kyiv, Ukraine. He was a full Member of ...

, but the term ''polariton,'' proposed by

John Hopfield John Joseph Hopfield (born July 15, 1933) is an American scientist most widely known for his invention of an associative neural network in 1982. It is now more commonly known as the Hopfield network. Biography Hopfield was born in 1933 to Pol ...

, 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 and, independently, by

Huang Kun Huang Kun (; September 2, 1919 – July 6, 2005) was a Chinese physicist and an academician of the Chinese Academy of Sciences. He was awarded the State Preeminent Science and Technology Award (the highest science award in China) by President Jia ...

in 1951. Collective interactions were published by

David Pines David Pines (June 8, 1924 May 3, 2018) was the founding director of the Institute for Complex Adaptive Matter (ICAM) and the International Institute for Complex Adaptive Matter (I2CAM) (respectively, United States-wide and international instit ...

and

David Bohm David Joseph Bohm (; 20 December 1917 – 27 October 1992) was an American-Brazilian-British scientist who has been described as one of the most significant theoretical physicists of the 20th centuryPeat 1997, pp. 316-317 and who contributed u ...

in 1952, and

plasmon In physics, a plasmon is a quantum of plasma oscillation. Just as light (an optical oscillation) consists of photons, the plasma oscillation consists of plasmons. The plasmon can be considered as a quasiparticle since it arises from the quantiz ...

s were described in silver by

Herbert Fröhlich Herbert Fröhlich (9 December 1905 – 23 January 1991) FRS was a German-born British physicist. Career In 1927, Fröhlich entered Ludwig-Maximilians University in Munich to study physics, and received his doctorate under Arnold Sommerfeld ...

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. 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. In February 2018, scientists reported the discovery of a new three-photon form of

light Light or visible light is electromagnetic radiation that can be perceived by the human eye. Visible light is usually defined as having wavelengths in the range of 400–700 nanometres (nm), corresponding to frequencies of 750–420 tera ...

, which may involve polaritons, that could be useful in the development of

quantum computer Quantum computing is a type of computation whose operations can harness the phenomena of quantum mechanics, such as superposition, interference, and entanglement. Devices that perform quantum computations are known as quantum computers. Though ...

Types

A polariton is the result of the combination of a

photon A photon () is an elementary particle that is a quantum of the electromagnetic field, including electromagnetic radiation such as light and radio waves, and the force carrier for the electromagnetic force. Photons are massless, so they always ...

with a polar excitation in a material. The following are types of polaritons: *

Phonon polaritons Phonon polaritons are a type of quasiparticle that can form in a diatomic ionic crystal due to coupling of transverse optical phonons and photons. They are particular type of polariton, which behave like bosons. Phonon polaritons occur in the r ...

result from coupling of an

infrared Infrared (IR), sometimes called infrared light, is electromagnetic radiation (EMR) with wavelengths longer than those of visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from around ...

photon with an optical

; * Exciton polaritons result from coupling of

visible light Light or visible light is electromagnetic radiation that can be perceived by the human eye. Visible light is usually defined as having wavelengths in the range of 400–700 nanometres (nm), corresponding to frequencies of 750–420 te ...

with an

exciton An exciton is a bound state of an electron and an electron hole which are attracted to each other by the electrostatic Coulomb force. It is an electrically neutral quasiparticle that exists in insulators, semiconductors and some liquids. The ...

; *

Intersubband polariton Intersubband transitions (also known as intraband transitions) are dipolar allowed optical excitations between the quantized electronic energy levels within the conduction band of semiconductor heterostructures. Intersubband transitions when cou ...

s result from coupling of an

or terahertz photon with an intersubband excitation; *

Surface plasmon polaritons Surface plasmon polaritons (SPPs) are electromagnetic waves that travel along a metal–dielectric or metal–air interface, practically in the infrared or visible-frequency. The term "surface plasmon polariton" explains that the wave involves b ...

result from coupling of

surface plasmon Surface plasmons (SPs) are coherent delocalized electron oscillations that exist at the interface between any two materials where the real part of the dielectric function changes sign across the interface (e.g. a metal-dielectric interface, such ...

s with light (the wavelength depends on the substance and its geometry); * Bragg polaritons ("Braggoritons") result from coupling of Bragg photon modes with bulk

s; *

Plexciton Plexcitons are polaritonic modes that result from coherently coupled plasmons and excitons. Plexcitons aid direct energy flows in exciton energy transfer (EET). Plexcitons travel for 20 μm, similar to the width of a human hair. History Plas ...

s result from coupling

s with excitons; * Magnon polaritons result from coupling of

magnon A magnon is a quasiparticle, a collective excitation of the electrons' spin structure in a crystal lattice. In the equivalent wave picture of quantum mechanics, a magnon can be viewed as a quantized spin wave. Magnons carry a fixed amount of e ...

with light; * pi-tons result from coupling of alternating charge or spin fluctuations with light, distinctly different from magnon or exciton polaritons; * Cavity polaritons.

References

External links

YouTube animation explaining what is polariton in a semiconductor micro-resonator.

Description of the experimental research on polariton fluids at the Institute of Nanotechnologies.
{{Authority control Quasiparticles

History

Types

See also

References

Further reading

External links