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Polariton
In physics, polaritons 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 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. The polariton is a bosonic quasiparticle, and should not be confused with the polaron (a fermionic quasiparticle), which is an electron plus an attached phonon 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 propag ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phonon Polaritons
Phonon polaritons are a type of quasiparticle that can form in a diatomic ionic crystal due to coupling of Phonon, transverse optical phonons and photons. They are particular type of polariton, which behave like bosons. Phonon polaritons occur in the region where the wavelength and energy of phonons and photons are similar, as to adhere to the Avoided crossing, avoided crossing principle. Phonon polariton spectra have traditionally been studied using Raman spectroscopy. The recent advances in (scattering-type) Near-field scanning optical microscope, scanning near-field optical microscopy((s-)SNOM) and atomic force microscopy(AFM) have made it possible to observe the polaritons in a more direct way. Theory Phonon polaritons only result from coupling of transverse optical phonons, this is due to the particular form of the dispersion relation of the phonon and photon and their interaction. Photons consist of electromagnetic waves, which are always transverse. Therefore, they can ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 the Ukrainian Academy of Sciences and is known for his fundamental contributions to condensed matter physics, especially for introducing and advancing the concept of polaron as a charge carrier in solids. Career In 1941 Pekar submitted his Candidate of Science thesis on nonlinear theory of semiconductor rectifiers for which he was awarded Doctor of Science Degree, this work was strongly approved by Lev Landau. In 1946, Pekar developed a concept of a polaron and coined this term. The model developed in this paper is macroscopic and based on electrostatic coupling of an electron to polar optical phonons. This coupling results in dressing of the electron by a cloud of virtual phonons and renormalization of its energy spectrum. In the s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 Sciences of Ukraine. He was recognized for his works on condensed matter theory; the theory of phonon spectra in crystals; electronic structure and defects in insulators and semiconductors; and biophysics. He created the Department of Theoretical Physics and the Department of Biophysics at Donetsk National University. Tolpygo was a teacher, mentor and scientific adviser to graduate students. Tolpygo was awarded the Order of the Great Patriotic War (2nd Degree). Early life Tolpygo was born during WWI in Kyiv, Ukraine, then part of the Russian Empire. His father, Boris Nikolaevich Tolpygo (1889 – 1958) was a jurist who received the Order of St. Stanislaus for his services to the Russian army during World War I. Tolpygo's mother, Tatiana B. B ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 quantization of plasma oscillations, just like phonons are quantizations of mechanical vibrations. Thus, plasmons are collective (a discrete number) oscillations of the free electron gas density. For example, at optical frequencies, plasmons can couple with a photon to create another quasiparticle called a plasmon polariton. Derivation The plasmon was initially proposed in 1952 by David Pines and David Bohm and was shown to arise from a Hamiltonian for the long-range electron-electron correlations. Since plasmons are the quantization of classical plasma oscillations, most of their properties can be derived directly from Maxwell's equations. Explanation Plasmons can be described in the classical picture as an oscillation of electron densit ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 example, as an electron travels through a semiconductor, its motion is disturbed in a complex way by its interactions with other electrons and with atomic nucleus, atomic nuclei. The electron behaves as though it has a different effective mass (solid-state physics), effective mass travelling unperturbed in vacuum. Such an electron is called an ''electron quasiparticle''. In another example, the aggregate motion of electrons in the valence band of a semiconductor or a hole band in a metal behave as though the material instead contained positively charged quasiparticles called ''electron holes''. Other quasiparticles or collective excitations include the ''phonon'', a quasiparticle derived from the vibrations of atoms in a solid, and the ''plasmo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 antifouling paints. The compound can appear either yellow or red, depending on the size of the particles. Copper(I) oxide is found as the reddish mineral cuprite. Preparation Copper(I) oxide may be produced by several methods. Most straightforwardly, it arises via the oxidation of copper metal: : 4 Cu + O2 → 2 Cu2O Additives such as water and acids affect the rate of this process as well as the further oxidation to copper(II) oxides. It is also produced commercially by reduction of copper(II) solutions with sulfur dioxide. Reactions Aqueous cuprous chloride solutions react with base to give the same material. In all cases, the color is highly sensitive to the procedural details. Formation of copper(I) oxide is the basis of the F ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 exciton is regarded as an elementary excitation of condensed matter that can transport energy without transporting net electric charge. An exciton can form when a material absorbs a photon of higher energy than its bandgap. This excites an electron from the valence band into the conduction band. In turn, this leaves behind a positively charged electron hole (an abstraction for the location from which an electron was moved). The electron in the conduction band is then less attracted to this localized hole due to the repulsive Coulomb forces from large numbers of electrons surrounding the hole and excited electron. These repulsive forces provide a stabilizing energy balance. Consequently, the exciton has slightly less energy than the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 electron moving in a dielectric crystal where the atoms displace from their equilibrium positions to effectively screen the charge of an electron, known as a phonon cloud. This lowers the electron mobility and increases the electron's effective mass. The general concept of a polaron has been extended to describe other interactions between the electrons and ions in metals that result in a bound state, or a lowering of energy compared to the non-interacting system. Major theoretical work has focused on solving Fröhlich and Holstein Hamiltonians. This is still an active field of research to find exact numerical solutions to the case of one or two electrons in a large crystal lattice, and to study the case of many interacting electrons. Experime ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 Polish physicist John J. Hopfield (spectroscopist), John Joseph Hopfield and physicist Helen Hopfield. Helen was the older Hopfield's second wife. He is the sixth of Hopfield's children and has three children and six grandchildren of his own. He received his Bachelor of Arts, A.B. from Swarthmore College in 1954, and a Ph.D. in physics from Cornell University in 1958 (supervised by Albert Overhauser). He spent two years in the theory group at Bell Laboratories, and subsequently was a faculty member at University of California, Berkeley (physics), Princeton University (physics), California Institute of Technology (Chemistry and Biology) and again at Princeton, where he is the Howard A. Prior Professor of Molecular Biology, Emeritus. For 35 yea ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 terahertz, between the infrared (with longer wavelengths) and the ultraviolet (with shorter wavelengths). In physics, the term "light" may refer more broadly to electromagnetic radiation of any wavelength, whether visible or not. In this sense, gamma rays, X-rays, microwaves and radio waves are also light. The primary properties of light are intensity, propagation direction, frequency or wavelength spectrum and polarization. Its speed in a vacuum, 299 792 458 metres a second (m/s), is one of the fundamental constants of nature. Like all types of electromagnetic radiation, visible light propagates by massless elementary particles called photons that represents the quanta of electromagnetic field, and can be analyzed as both waves and par ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Level Repulsion
Level repulsion is the quantum mechanical equivalent to a repulsion effect in oscillators. A system of two coupled oscillators has two natural frequencies. As the coupling strength between the oscillators increases, the lower frequency decreases and the higher increases. See also * Avoided crossing * Intersubband polariton * Wigner–Ville distribution The Wigner quasiprobability distribution (also called the Wigner function or the Wigner–Ville distribution, after Eugene Wigner and Jean-André Ville) is a quasiprobability distribution. It was introduced by Eugene Wigner in 1932 to study qua ... References Quantum mechanics {{Quantum-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dispersion (optics)
In optics, and by analogy other branches of physics dealing with wave propagation, dispersion is the phenomenon in which the phase velocity of a wave depends on its frequency; sometimes the term chromatic dispersion is used for specificity to optics in particular. A medium having this common property may be termed a dispersive medium (plural ''dispersive media''). Although the term is used in the field of optics to describe light and other electromagnetic waves, dispersion in the same sense can apply to any sort of wave motion such as acoustic dispersion in the case of sound and seismic waves, and in gravity waves (ocean waves). Within optics, dispersion is a property of telecommunication signals along transmission lines (such as microwaves in coaxial cable) or the pulses of light in optical fiber. Physically, dispersion translates in a loss of kinetic energy through absorption. In optics, one important and familiar consequence of dispersion is the change in the angle of refra ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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