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Polariton Interferometer
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 pr ... [...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 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 principle. Phonon polariton spectra have traditionally been studied using Raman spectroscopy. The recent advances in (scattering-type) 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 only couple with transverse phonons in crystals. Near \mathbf ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 equal to one event per second. The period is the interval of time between events, so the period is the reciprocal of the frequency. For example, if a heart beats at a frequency of 120 times a minute (2 hertz), the period, —the interval at which the beats repeat—is half a second (60 seconds divided by 120 beats). Frequency is an important parameter used in science and engineering to specify the rate of oscillatory and vibratory phenomena, such as mechanical vibrations, audio signals (sound), radio waves, and light. Definitions and units For cyclical phenomena such as oscillations, waves, or for examples of simple harmonic motion, the term ''frequency'' is defined as the number of cycles or vibrations per unit of time. The ... [...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 th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
National Research Council (Italy)
The National Research Council (Italian: ''Consiglio Nazionale delle Ricerche, CNR'') is the largest research council in Italy. As a public organisation, its remit is to support scientific and technological research. Its headquarters are in Rome. History The institution was founded in 1923. The first president was Vito Volterra, succeeded by Guglielmo Marconi. The process of improvement of the national scientific research, through the use of specific laws, (see Law 59/1997), affects many research organisations, and amongst them is CNR, whose "primary function is to carry on, through its own organs, advanced basic and applied research, both to develop and maintain its own scientific competitiveness, and to be ready to take part effectively in a timely manner in the strategic fields defined by the national planning system". On 23 December 1987, CNR registered the first Italian internet domain: cnr.it Reorganisation With the issuing of the legislative decree of 30 January 1999, n ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 in 1930. His first position was as Privatdozent at the University of Freiburg. Due to rising anti-Semitism and the Deutsche Physik movement under Adolf Hitler, and at the invitation of Yakov Frenkel, Fröhlich went to the Soviet Union, in 1933, to work at the Ioffe Physico-Technical Institute in Leningrad. During the Great Purge following the murder of Sergei Kirov, he fled to England in 1935. Except for a short visit to the Netherlands and a brief internment during World War II, he worked in Nevill Francis Mott's department, at the University of Bristol, until 1948, rising to the position of Reader. At the invitation of James Chadwick, he took the Chair for Theoretical Physics at the University of Liverpool. In 1950 Bell Telephone Lab ... [...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 de ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 unorthodox ideas to quantum theory, neuropsychology and the philosophy of mind. Among his many contributions to physics is his causal and deterministic interpretation of quantum theory, now known as De Broglie–Bohm theory. Bohm advanced the view that quantum physics meant that the old Cartesian model of reality—that there are two kinds of substance, the mental and the physical, that somehow interact—was too limited. To complement it, he developed a mathematical and physical theory of "implicate" and "explicate" order.David Bohm: ''Wholeness and the Implicate Order'', Routledge, 1980 (). He also believed that the brain, at the cellular level, works according to the mathematics of some quantum effects, and postulated that thought is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 institutions dedicated to research in and the understanding of emergent phenomena), distinguished professor of physics, University of California, Davis, research professor of physics and professor emeritus of physics and electrical and computer engineering in the Center for Advanced Study, University of Illinois at Urbana–Champaign (UIUC), and a staff member in the office of the Materials, Physics, and Applications Division at the Los Alamos National Laboratory. His seminal contributions to the theory of many-body systems and to theoretical astrophysics were recognized by two Guggenheim Fellowships, the Feenberg Medal, the Edward A. Frieman Prize for Excellence in Graduate Student Research, Dirac and Drucker prizes, and by his election to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 Jiang Zemin in 2001. Born in Beijing, China, in 1919, Huang graduated from Yenching University with a degree in physics. In 1948, he earned his PhD from the H. H. Wills Physics Lab of Bristol University in England and continued his postdoctoral studies at Liverpool University, where he coauthored the book ''Dynamical Theory of Crystal Lattices'' with Max Born between 1949 and 1951. In 1951, Huang returned to China to teach, and became a professor of physics at Peking University. In 1955, he became a founding member of the Chinese Academy of Sciences (CAS). After his retirement in 1983, Huang remained active in the research of semiconductors and was selected as the chairman of the Chinese Society of Physics between 1987 and 1991. He served a ... [...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 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 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 years, he also continued a strong connection with Bell ... [...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 ... [...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] |
