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A magnet levitating above a high-temperature superconductor, cooled with liquid nitrogen. Persistent electric current flows on the surface of the superconductor, acting to exclude the magnetic field of the magnet (the Meissner effect). This current effectively forms an electromagnet that repels the magnet.

Superconductivity is a phenomenon occurring in certain materials at extremely low temperatures, characterized by exactly zero electrical resistance and the exclusion of the interior magnetic field (the Meissner effect). Image File history File links Emblem-important. ... Image File history File links Metadata Size of this preview: 800 × 572 pixelsFull resolution‎ (2,400 × 1,716 pixels, file size: 465 KB, MIME type: image/jpeg) {{Information |Description={{fr|[[Meissner effect|Effet Meissner: lévitation dun aimant au dessus dun supra-conducteur}} Meissner effect: levitation of a... Image File history File links Metadata Size of this preview: 800 × 572 pixelsFull resolution‎ (2,400 × 1,716 pixels, file size: 465 KB, MIME type: image/jpeg) {{Information |Description={{fr|[[Meissner effect|Effet Meissner: lévitation dun aimant au dessus dun supra-conducteur}} Meissner effect: levitation of a... For other uses, see Magnet (disambiguation). ... Unsolved problems in physics: Why do certain materials exhibit superconductivity at temperatures much higher than 50 kelvins? The term high-temperature superconductor was initially employed to designate the new family of cuprate-perovskite ceramic materials discovered by J.G. Bednorz and K.A. Müller in 1986. ... A tank of liquid nitrogen, used to supply a cryogenic freezer (for storing laboratory samples at a temperature of about -150 Celsius). ... Diagram of the Meissner effect. ... Look up material in Wiktionary, the free dictionary. ... For other uses, see Temperature (disambiguation). ... Electrical resistance is a measure of the degree to which an electrical component opposes the passage of current. ... For the indie-pop band, see The Magnetic Fields. ... Diagram of the Meissner effect. ...

The electrical resistivity of a metallic conductor decreases gradually as the temperature is lowered. However, in ordinary conductors such as copper and silver, impurities and other defects impose a lower limit. Even near absolute zero a real sample of copper shows a non-zero resistance. The resistance of a superconductor, on the other hand, drops abruptly to zero when the material is cooled below its "critical temperature". An electric current flowing in a loop of superconducting wire can persist indefinitely with no power source. Like ferromagnetism and atomic spectral lines, superconductivity is a quantum mechanical phenomenon. It cannot be understood simply as the idealization of "perfect conductivity" in classical physics. Electrical resistivity (also known as specific electrical resistance) is a measure of how strongly a material opposes the flow of electric current. ... In science and engineering, conductors, such as copper or aluminum, are materials with atoms having loosely held valence electrons. ... For other uses, see Copper (disambiguation). ... This article is about the chemical element. ... For other uses, see Absolute Zero (disambiguation). ... This box:      Electric current is the flow (movement) of electric charge. ... Ferromagnetism is the phenomenon by which materials, such as iron, in an external magnetic field become magnetized and remain magnetized for a period after the material is no longer in the field. ... In physics, atomic spectral lines are of two types: An emission line is formed when an electron makes a transition from a particular discrete energy level of an atom, to a lower energy state, emitting a photon of a particular energy and wavelength. ... For a generally accessible and less technical introduction to the topic, see Introduction to quantum mechanics. ... A perfect conductor is an electrical conductor with no resistivity. ...

Superconductivity occurs in a wide variety of materials, including simple elements like tin and aluminium, various metallic alloys and some heavily-doped semiconductors. Superconductivity does not occur in noble metals like gold and silver, nor in most ferromagnetic metals. This article is about the metallic chemical element. ... Aluminum redirects here. ... An alloy is a homogeneous hybrid of two or more elements, at least one of which is a metal, and where the resulting material has metallic properties. ... In semiconductor production, doping refers to the process of intentionally introducing impurities into an extremely pure (also referred to as intrinsic) semiconductor in order to change its electrical properties. ... A semiconductor is a solid material that has electrical conductivity in between that of a conductor and that of an insulator; it can vary over that wide range either permanently or dynamically. ... Noble metals are metals that are resistant to corrosion or oxidation, unlike most base metals. ... GOLD refers to one of the following: GOLD (IEEE) is an IEEE program designed to garner more student members at the university level (Graduates of the Last Decade). ...

In 1986 the discovery of a family of cuprate-perovskite ceramic materials known as high-temperature superconductors, with critical temperatures in excess of 90 kelvin, spurred renewed interest and research in superconductivity for several reasons. As a topic of pure research, these materials represented a new phenomenon not explained by the current theory. And, because the superconducting state persists up to more manageable temperatures, past the economically-important boiling point of liquid nitrogen (77 kelvin), more commercial applications are feasible, especially if materials with even higher critical temperatures could be discovered. The term high-temperature superconductor was initially employed to designate the new family of cuprate-perovskite ceramic materials discovered by J.G. Bednorz and K.A. Mueller in 1986. ... Perovskite (calcium titanium oxide, CaTiO3) is a relatively rare mineral occurring in orthorhombic (pseudocubic) crystals. ... This article is about ceramic materials. ... The term high-temperature superconductor was initially employed to designate the new family of cuprate-perovskite ceramic materials discovered by J.G. Bednorz and K.A. Mueller in 1986. ... Italic text This article is about the boiling point of liquids. ... A tank of liquid nitrogen, used to supply a cryogenic freezer (for storing laboratory samples at a temperature of about -150 Celsius). ...

Elementary properties of superconductors

Most of the physical properties of superconductors vary from material to material, such as the heat capacity and the critical temperature at which superconductivity is destroyed. On the other hand, there is a class of properties that are independent of the underlying material. For instance, all superconductors have exactly zero resistivity to low applied currents when there is no magnetic field present. The existence of these "universal" properties implies that superconductivity is a thermodynamic phase, and thus possess certain distinguishing properties which are largely independent of microscopic details. To meet Wikipedias quality standards, this article or section may require cleanup. ... In the physical sciences, a phase is a set of states of a macroscopic physical system that have relatively uniform chemical composition and physical properties (i. ...

Zero electrical "dc" resistance

Electric cables for accelerators at CERN: top, regular cables for LEP; bottom, superconducting cables for the LHC.

The simplest method to measure the electrical resistance of a sample of some material is to place it in an electrical circuit in series with a current source I and measure the resulting voltage V across the sample. The resistance of the sample is given by Ohm's law as . If the voltage is zero, this means that the resistance is zero and that the sample is in the superconducting state. Image File history File links Download high resolution version (2560x1920, 680 KB) Work by Rama File links The following pages link to this file: Superconductivity ... Image File history File links Download high resolution version (2560x1920, 680 KB) Work by Rama File links The following pages link to this file: Superconductivity ... CERN logo The European Organization for Nuclear Research (French: ), commonly known as CERN (see Naming), pronounced (or in French), is the worlds largest particle physics laboratory, situated just northwest of Geneva on the border between France and Switzerland. ... The Large Electron-Positron Collider (usually called LEP for short. ... , The Large Hadron Collider (LHC) is a particle accelerator and Hadron collider located at CERN, near Geneva, Switzerland. ... An electrical network or electrical circuit is an interconnection of analog electrical elements such as resistors, inductors, capacitors, diodes, switches and transistors. ... International safety symbol Caution, risk of electric shock (ISO 3864), colloquially known as high voltage symbol. ... This article is about the law related to electricity. ...

Superconductors are also able to maintain a current with no applied voltage whatsoever, a property exploited in superconducting electromagnets such as those found in MRI machines. Experiments have demonstrated that currents in superconducting coils can persist for years without any measurable degradation. Experimental evidence points to a current lifetime of at least 100,000 years, and theoretical estimates for the lifetime of a persistent current exceed the estimated lifetime of the universe. An electromagnet is a type of magnet in which the magnetic field is produced by the flow of an electric current. ... MRI redirects here. ... For other uses, see Universe (disambiguation). ...

In a normal conductor, an electrical current may be visualized as a fluid of electrons moving across a heavy ionic lattice. The electrons are constantly colliding with the ions in the lattice, and during each collision some of the energy carried by the current is absorbed by the lattice and converted into heat, which is essentially the vibrational kinetic energy of the lattice ions. As a result, the energy carried by the current is constantly being dissipated. This is the phenomenon of electrical resistance. For other uses, see Electron (disambiguation). ... This article is about the electrically charged particle. ... For other uses, see Heat (disambiguation) In physics, heat, symbolized by Q, is energy transferred from one body or system to another due to a difference in temperature. ... The cars of a roller coaster reach their maximum kinetic energy when at the bottom of their path. ...

The situation is different in a superconductor. In a conventional superconductor, the electronic fluid cannot be resolved into individual electrons. Instead, it consists of bound pairs of electrons known as Cooper pairs. This pairing is caused by an attractive force between electrons from the exchange of phonons. Due to quantum mechanics, the energy spectrum of this Cooper pair fluid possesses an energy gap, meaning there is a minimum amount of energy ΔE that must be supplied in order to excite the fluid. Therefore, if ΔE is larger than the thermal energy of the lattice, given by kT, where k is Boltzmann's constant and T is the temperature, the fluid will not be scattered by the lattice. The Cooper pair fluid is thus a superfluid, meaning it can flow without energy dissipation. A Cooper pair is the name given to electrons that are bound together in a certain manner first described by Leon Cooper. ... Normal modes of vibration progression through a crystal. ... For a generally accessible and less technical introduction to the topic, see Introduction to quantum mechanics. ... This article needs to be cleaned up to conform to a higher standard of quality. ... In solid state physics and related applied fields, the band gap (or energy gap) is the energy difference between the top of the valence band and the bottom of the conduction band in insulators and semiconductors. ... In thermal physics, thermal energy is the energy portion of a system that increases with its temperature. ... The Boltzmann constant (k or kB) is the physical constant relating temperature to energy. ... For other uses, see Temperature (disambiguation). ... Helium II will creep along surfaces in order to find its own level - after a short while, the levels in the two containers will equalize. ...

In a class of superconductors known as Type II superconductors, including all known high-temperature superconductors, an extremely small amount of resistivity appears at temperatures not too far below the nominal superconducting transition when an electrical current is applied in conjunction with a strong magnetic field, which may be caused by the electrical current. This is due to the motion of vortices in the electronic superfluid, which dissipates some of the energy carried by the current. If the current is sufficiently small, the vortices are stationary, and the resistivity vanishes. The resistance due to this effect is tiny compared with that of non-superconducting materials, but must be taken into account in sensitive experiments. However, as the temperature decreases far enough below the nominal superconducting transition, these vortices can become frozen into a disordered but stationary phase known as a "vortex glass". Below this vortex glass transition temperature, the resistance of the material becomes truly zero. Unsolved problems in physics: Why do certain materials exhibit superconductivity at temperatures much higher than 50 kelvins? The term high-temperature superconductor was initially employed to designate the new family of cuprate-perovskite ceramic materials discovered by J.G. Bednorz and K.A. Müller in 1986. ...

Superconducting phase transition

Behavior of heat capacity (c_v, blue) and resistivity (ρ, green) at the superconducting phase transition

In superconducting materials, the characteristics of superconductivity appear when the temperature T is lowered below a critical temperature T_c. The value of this critical temperature varies from material to material. Conventional superconductors usually have critical temperatures ranging from around 20 K (Kelvin) to less than 1 K. Solid mercury, for example, has a critical temperature of 4.2 K. As of 2001, the highest critical temperature found for a conventional superconductor is 39 K for magnesium diboride (MgB₂), although this material displays enough exotic properties that there is doubt about classifying it as a "conventional" superconductor. Cuprate superconductors can have much higher critical temperatures: YBa₂Cu₃O₇, one of the first cuprate superconductors to be discovered, has a critical temperature of 92 K, and mercury-based cuprates have been found with critical temperatures in excess of 130 K. The explanation for these high critical temperatures remains unknown. Electron pairing due to phonon exchanges explains superconductivity in conventional superconductors, but it does not explain superconductivity in the newer superconductors that have a very high critical temperature. Image File history File links Download high resolution version (792x612, 13 KB) Summary Resistivity and specific heat in zero applied magnetic field for a typical superconductor. ... Image File history File links Download high resolution version (792x612, 13 KB) Summary Resistivity and specific heat in zero applied magnetic field for a typical superconductor. ... For other uses, see Temperature (disambiguation). ... For other uses, see Kelvin (disambiguation). ... This article is about the element. ... This article is about the year. ... Magnesium diboride (MgB2) is an inexpensive and simple superconductor that can be synthesized by high temperature reaction between boron and magnesium (in the liquid or gaseous state). ... The term high-temperature superconductor was initially employed to designate the new family of cuprate-perovskite ceramic materials discovered by J.G. Bednorz and K.A. Mueller in 1986. ... Yttrium barium copper oxide, or YBCO, chemical formula YBa2Cu3O7-δ, is a high-temperature superconductor with a superconducting temperature of 94K. Its discovery by C.W. Chu in 1987 launched the era of high-temperature superconductors. ... Normal modes of vibration progression through a crystal. ...

The onset of superconductivity is accompanied by abrupt changes in various physical properties, which is the hallmark of a phase transition. For example, the electronic heat capacity is proportional to the temperature in the normal (non-superconducting) regime. At the superconducting transition, it suffers a discontinuous jump and thereafter ceases to be linear. At low temperatures, it varies instead as e^{−α /T} for some constant α. This exponential behavior is one of the pieces of evidence for the existence of the energy gap. This diagram shows the nomenclature for the different phase transitions. ... To meet Wikipedias quality standards, this article or section may require cleanup. ... In solid state physics and related applied fields, the band gap (or energy gap) is the energy difference between the top of the valence band and the bottom of the conduction band in insulators and semiconductors. ...

The order of the superconducting phase transition was long a matter of debate. Experiments indicate that the transition is second-order, meaning there is no latent heat. Calculations in the 1970s suggested that it may actually be weakly first-order due to the effect of long-range fluctuations in the electromagnetic field. Only recently it was shown theoretically with the help of a disorder field theory, in which the vortex lines of the superconductor play a major role, that the transition is of second order within the type II regime and of first order (i.e., latent heat) within the type I regime, and that the two regions are separated by a tricritical point. This diagram shows the nomenclature for the different phase transitions. ... In thermochemistry, latent heat is the amount of energy in the form of heat released or absorbed by a substance during a change of phase (i. ... Vorticity is a mathematical concept used in fluid dynamics. ... In thermochemistry, latent heat is the amount of energy in the form of heat released or absorbed by a substance during a change of phase (i. ...

Meissner effect

When a superconductor is placed in a weak external magnetic field H, the field penetrates the superconductor for only a short distance λ, called the London penetration depth, after which it decays rapidly to zero. This is called the Meissner effect, and is a defining characteristic of superconductivity. For most superconductors, the London penetration depth is on the order of 100 nm. For the indie-pop band, see The Magnetic Fields. ... In superconductivity, London penetration depth (usually denoted as or ) characterizes the typical distance on which weak magnetic field penetrates into a superconductor. ... Diagram of the Meissner effect. ...

The Meissner effect is sometimes confused with the kind of diamagnetism one would expect in a perfect electrical conductor: according to Lenz's law, when a changing magnetic field is applied to a conductor, it will induce an electrical current in the conductor that creates an opposing magnetic field. In a perfect conductor, an arbitrarily large current can be induced, and the resulting magnetic field exactly cancels the applied field. Levitating pyrolytic carbon Diamagnetism is a form of magnetism that is only exhibited by a substance in the presence of an externally applied magnetic field. ... Lenzs law (pronounced (IPA) ) gives the direction of the induced electromotive force (emf) and current resulting from electromagnetic induction. ...

The Meissner effect is distinct from this because a superconductor expels all magnetic fields, not just those that are changing. Suppose we have a material in its normal state, containing a constant internal magnetic field. When the material is cooled below the critical temperature, we would observe the abrupt expulsion of the internal magnetic field, which we would not expect based on Lenz's law.

The Meissner effect was explained by the brothers Fritz and Heinz London, who showed that the electromagnetic free energy in a superconductor is minimized provided Fritz Wolfgang London (March 7, 1900–March 30, 1954) was a German-born American physicist for whom the London force is named. ... The thermodynamic free energy is a measure of the amount of mechanical (or other) work that can be extracted from a system, and is helpful in engineering applications. ...

where H is the magnetic field and λ is the London penetration depth.

This equation, which is known as the London equation, predicts that the magnetic field in a superconductor decays exponentially from whatever value it possesses at the surface. This article or section does not cite its references or sources. ... A quantity is said to be subject to exponential decay if it decreases at a rate proportional to its value. ...

The Meissner effect breaks down when the applied magnetic field is too large. Superconductors can be divided into two classes according to how this breakdown occurs. In Type I superconductors, superconductivity is abruptly destroyed when the strength of the applied field rises above a critical value H_c. Depending on the geometry of the sample, one may obtain an intermediate state consisting of regions of normal material carrying a magnetic field mixed with regions of superconducting material containing no field. In Type II superconductors, raising the applied field past a critical value H_c1 leads to a mixed state in which an increasing amount of magnetic flux penetrates the material, but there remains no resistance to the flow of electrical current as long as the current is not too large. At a second critical field strength H_c2, superconductivity is destroyed. The mixed state is actually caused by vortices in the electronic superfluid, sometimes called fluxons because the flux carried by these vortices is quantized. Most pure elemental superconductors, except niobium, technetium, vanadium and carbon nanotubes, are Type I, while almost all impure and compound superconductors are Type II. Magnetic flux, represented by the Greek letter Φ (phi), is a measure of quantity of magnetism, taking account of the strength and the extent of a magnetic field. ... Wikipedia does not have an article with this exact name. ... In physics, a quantum (plural: quanta) is an indivisible entity of energy. ... The periodic table of the chemical elements A chemical element, or element, is a type of atom that is distinguished by its atomic number; that is, by the number of protons in its nucleus. ... General Name, Symbol, Number niobium, Nb, 41 Chemical series transition metals Group, Period, Block 5, 5, d Appearance gray metallic Standard atomic weight 92. ... General Name, Symbol, Number technetium, Tc, 43 Chemical series transition metals Group, Period, Block 7, 5, d Appearance silvery gray metal Standard atomic weight [98](0) g·mol−1 Electron configuration [Kr] 4d5 5s2 Electrons per shell 2, 8, 18, 13, 2 Physical properties Phase solid Density (near r. ... General Name, symbol, number vanadium, V, 23 Chemical series transition metals Group, period, block 5, 4, d Appearance silver-grey metal Standard atomic weight 50. ... // 3D model of three types of single-walled carbon nanotubes. ...

Theories of superconductivity

Since the discovery of superconductivity, great efforts have been devoted to finding out how and why it works. During the 1950s, theoretical condensed matter physicists arrived at a solid understanding of "conventional" superconductivity, through a pair of remarkable and important theories: the phenomenological Ginzburg-Landau theory (1950) and the microscopic BCS theory (1957). Generalizations of these theories form the basis for understanding the closely related phenomenon of superfluidity, because they fall into the Lambda transition universality class, but the extent to which similar generalizations can be applied to unconventional superconductors as well is still controversial. The four-dimensional extension of the Ginzburg-Landau theory, the Coleman-Weinberg model, is important in quantum field theory and cosmology. Condensed matter physics is the field of physics that deals with the macroscopic physical properties of matter. ... In physics, Ginzburg-Landau theory is a mathematical theory used to model superconductivity. ... BCS theory (named for its creators, Bardeen, Cooper, and Schrieffer) successfully explains conventional superconductivity, the ability of certain metals at low temperatures to conduct electricity without resistance. ... Superfluidity is a phase of matter characterised by the complete absence of viscosity. ... // Introduction Background Many macroscopic phenomena may be grouped into a small set of universality classes. ... Unconventional superconductors are materials that display superconductivity but that do not conform to BCS theory or its extensions. ... In physics, Ginzburg-Landau theory is a mathematical theory used to model superconductivity. ... The Coleman-Weinberg model represents quantum electrodynamics of a scalar field in four-dimensions. ... Quantum field theory (QFT) is the quantum theory of fields. ... Cosmology, from the Greek: κοσμολογία (cosmologia, κόσμος (cosmos) order + λογια (logia) discourse) is the study of the Universe in its totality, and by extension, humanitys place in it. ...

History of superconductivity

Main article: History of superconductivity

Superconductivity was discovered in 1911 by Heike Kamerlingh Onnes, who was studying the resistance of solid mercury at cryogenic temperatures using the recently-discovered liquid helium as a refrigerant. At the temperature of 4.2 K, he observed that the resistance abruptly disappeared.^[1] In subsequent decades, superconductivity was found in several other materials. In 1913, lead was found to superconduct at 7 K, and in 1941 niobium nitride was found to superconduct at 16 K. The history of superconductivity, the property exhibited by certain substances of lacking electrical resistance at temperatures close to absolute zero, began at the end of the 19th century and culminated in Heike Kamerlingh Onness 1911 discovery. ... Heike Kamerlingh Onnes (September 21, 1853 – February 21, 1926) was a Dutch physicist. ... This article is about the element. ... Cryogenics is the study of very low temperatures or the production of the same, and is often confused with cryobiology, the study of the effect of low temperatures on organisms, or the study of cryopreservation. ... General Name, symbol, number helium, He, 2 Chemical series noble gases Group, period, block 18, 1, s Appearance colorless Standard atomic weight 4. ... A refrigerant is a compound used in a heat cycle that undergoes a phase change from a gas to a liquid and back. ... General Name, Symbol, Number lead, Pb, 82 Chemical series Post-transition metals or poor metals Group, Period, Block 14, 6, p Appearance bluish gray Standard atomic weight 207. ...

The next important step in understanding superconductivity occurred in 1933, when Meissner and Ochsenfeld discovered that superconductors expelled applied magnetic fields, a phenomenon which has come to be known as the Meissner effect.^[2] In 1935, F. and H. London showed that the Meissner effect was a consequence of the minimization of the electromagnetic free energy carried by superconducting current.^[3] Walter Meißner was born in Berlin in 1882, where he studied machine construction and physics, promoting with Max Planck. ... Robert Ochsenfeld was a German physicist born on 18 May 1901 in Helberhausen. ... Diagram of the Meissner effect. ... The thermodynamic free energy is a measure of the amount of mechanical (or other) work that can be extracted from a system, and is helpful in engineering applications. ...

In 1950, the phenomenological Ginzburg-Landau theory of superconductivity was devised by Landau and Ginzburg.^[4]This theory, which combined Landau's theory of second-order phase transitions with a Schrödinger-like wave equation, had great success in explaining the macroscopic properties of superconductors. In particular, Abrikosov showed that Ginzburg-Landau theory predicts the division of superconductors into the two categories now referred to as Type I and Type II. Abrikosov and Ginzburg were awarded the 2003 Nobel Prize for their work (Landau having died in 1968). The term phenomenology in modern science, especially in physics, is used to describe a body of knowledge which relates several different empirical observations of phenomena to each other, in a way which is consistent with fundamental theory, but is not directly derived from theory. ... In physics, Ginzburg-Landau theory is a mathematical theory used to model superconductivity. ... Lev Davidovich Landau (Ле́в Дави́дович Ланда́у) (January 22, 1908 – April 1, 1968) was a prominent Soviet physicist and winner of the Nobel Prize for Physics whose broad field of work included the theory of superconductivity and superfluidity, quantum electrodynamics, nuclear physics and particle physics. ... Vitaly Lazarevich Ginzburg (Виталий Лазаревич Гинзбург) (born October 4, 1916 in Moscow) is a Soviet/Russian theoretical physicist and astrophysicist, a member of the Academy of Sciences of the former Soviet Union, and the successor to Igor Tamm as head of the Academys physics institute (FIAN). ... This diagram shows the nomenclature for the different phase transitions. ... This box:      For a non-technical introduction to the topic, please see Introduction to quantum mechanics. ... Alexei Alexeevich Abrikosov (Алексей Алексеевич Абрикосов) (born June 25, 1928, in Moscow, Russian SFSR, USSR.) is a Russian theoretical physicist whose main contributions are in the field of condensed matter physics. ... The Nobel Prize (Swedish: ) was established in Alfred Nobels will in 1895, and it was first awarded in Physics, Chemistry, Physiology or Medicine, Literature, and Peace in 1901. ...

Also in 1950, Maxwell and Reynolds et al. found that the critical temperature of a superconductor depends on the isotopic mass of the constituent element.^{[5] [6]} This important discovery pointed to the electron-phonon interaction as the microscopic mechanism responsible for superconductivity. For other uses, see Isotope (disambiguation). ... The periodic table of the chemical elements A chemical element, or element, is a type of atom that is distinguished by its atomic number; that is, by the number of protons in its nucleus. ... For other uses, see Electron (disambiguation). ... Normal modes of vibration progression through a crystal. ...

The complete microscopic theory of superconductivity was finally proposed in 1957 by Bardeen, Cooper, and Schrieffer.^[7] Independently, the superconductivity phenomenon was explained by Nikolay Bogolyubov. This BCS theory explained the superconducting current as a superfluid of Cooper pairs, pairs of electrons interacting through the exchange of phonons. For this work, the authors were awarded the Nobel Prize in 1972. John Bardeen (May 23, 1908 – January 30, 1991) was an American physicist and electrical engineer, who won the Nobel Prize in Physics twice: first in 1956 with William Shockley and Walter Brattain for the invention of the transistor; and again in 1972 with Leon Neil Cooper and John Robert Schrieffer... Leon Neil Cooper (born February 28, 1930) is an American physicist and winner of the 1972 Nobel Prize for Physics, along with John Bardeen and John Robert Schrieffer, for his role in developing the BCS theory (named for their initials) of superconductivity. ... John Robert Schrieffer (born May 31, 1931) is an American physicist and winner, with John Bardeen and Leon Neil Cooper, of the 1972 Nobel Prize for Physics for developing the BCS theory (for their initials), the first successful microscopic theory of superconductivity. ... Nikolai Nikolaevich Bogoliubov (21 August 1909 – 13 February 1992) was a Russian-Ukrainian mathematician and theoretical physicist known for his work in statistical field theory and dynamical systems. ... BCS theory (named for its creators, Bardeen, Cooper, and Schrieffer) successfully explains conventional superconductivity, the ability of certain metals at low temperatures to conduct electricity without resistance. ... A Cooper pair is the name given to electrons that are bound together in a certain manner first described by Leon Cooper. ...

The BCS theory was set on a firmer footing in 1958, when Bogoliubov showed that the BCS wavefunction, which had originally been derived from a variational argument, could be obtained using a canonical transformation of the electronic Hamiltonian.^[8] In 1959, Lev Gor'kov showed that the BCS theory reduced to the Ginzburg-Landau theory close to the critical temperature.^[9] The quantum Hamiltonian is the physical state of a system, which may be characterized as a ray in an abstract Hilbert space (or, in the case of ensembles, as a trace class operator with trace 1). ... Lev Gorkov is an American research physicist who is internationally known for his pioneering work in the field of superconductivity. ...

In 1962, the first commercial superconducting wire, a niobium-titanium alloy, was developed by researchers at Westinghouse. In the same year, Josephson made the important theoretical prediction that a supercurrent can flow between two pieces of superconductor separated by a thin layer of insulator.^[10] This phenomenon, now called the Josephson effect, is exploited by superconducting devices such as SQUIDs. It is used in the most accurate available measurements of the magnetic flux quantum , and thus (coupled with the quantum Hall resistivity) for Planck's constant h. Josephson was awarded the Nobel Prize for this work in 1973. Westinghouse logo (designed by Paul Rand) The Westinghouse Electric Company, headquartered in Monroeville, Pennsylvania, is an organization founded by George Westinghouse in 1886. ... Brian David Josephson (born Cardiff, Wales, UK, January 4, 1940) is a British physicist whose discovery of the Josephson effect as a 22-year-old graduate student won him the 1973 Nobel Prize for Physics, which he shared with Leo Esaki and Ivar Giaever. ... The Josephson effect is the phenomenon of current flow across two weakly coupled superconductors, separated by a very thin insulating barrier. ... For other uses, see Squid (disambiguation). ... The magnetic flux quantum Φ0 is the quantum of magnetic flux passing through a superconductor. ... The quantum Hall effect is a quantum-mechanical version of the Hall effect, observed in two-dimensional electron systems subjected to low temperatures and strong magnetic fields, in which the Hall conductance takes on the quantized values where is the elementary charge and is Plancks constant. ... A commemoration plaque for Max Planck on his discovery of Plancks constant, in front of Humboldt University, Berlin. ...

Until 1986, physicists had believed that BCS theory forbade superconductivity at temperatures above about 30 K. In that year, Bednorz and Müller discovered superconductivity in a lanthanum-based cuprate perovskite material, which had a transition temperature of 35 K (Nobel Prize in Physics, 1987).^[11] It was shortly found by Paul C. W. Chu of the University of Houston and M.K. Wu at the University of Alabama in Huntsville that replacing the lanthanum with yttrium, i.e. making YBCO, raised the critical temperature to 92 K, which was important because liquid nitrogen could then be used as a refrigerant (at atmospheric pressure, the boiling point of nitrogen is 77 K.)^[12] This is important commercially because liquid nitrogen can be produced cheaply on-site with no raw materials, and is not prone to some of the problems (solid air plugs, et cetera) of helium in piping. Many other cuprate superconductors have since been discovered, and the theory of superconductivity in these materials is one of the major outstanding challenges of theoretical condensed matter physics. Johannes Georg Bednorz (born May 16, 1950) is a German physicist who, along with Karl Alex Muller, was awarded the 1987 Nobel Prize for Physics for their joint discovery of superconductivity in certain substances at temperatures higher than had previously been thought attainable. ... Karl Alexander Müller (born April 20, 1927) is a Swiss physicist who, along with J. Georg Bednorz, was awarded the 1987 Nobel Prize for Physics for their joint discovery of superconductivity in certain substances at higher temperatures than had previously been thought attainable. ... General Name, Symbol, Number lanthanum, La, 57 Chemical series lanthanides Group, Period, Block 3, 6, f Appearance silvery white Atomic mass 138. ... Paul Chu Professor Paul Chu (Ching-Wu Chu, 朱經武; pinyin: ZhÅ« JÄ«ngwÇ”), born in Hunan, China in 1941, received his Bachelor of Science degree from Cheng-Kung University in Taiwan in 1962. ... For other system schools, see University of Houston System. ... The University of Alabama in Huntsville is a state-supported, public, coeducational university, accredited by the Southern Association of Colleges and Schools to award baccalaureate, masters and doctoral degrees. ... General Name, Symbol, Number yttrium, Y, 39 Chemical series transition metals Group, Period, Block 3, 5, d Appearance silvery white Standard atomic weight 88. ... Yttrium barium copper oxide, or YBCO, chemical formula YBa2Cu3O7-δ, is a high-temperature superconductor with a superconducting temperature of 94K. Its discovery by C.W. Chu in 1987 launched the era of high-temperature superconductors. ... A tank of liquid nitrogen, used to supply a cryogenic freezer (for storing laboratory samples at a temperature of about -150 Celsius). ... Helium exists in liquid form only at very low temperatures. ... Condensed matter physics is the field of physics that deals with the macroscopic physical properties of matter. ...

As of October 2007, the highest temperature superconductor is a ceramic material consisting of thallium, mercury, copper, barium, calcium, and oxygen, with T_c=138 K.^[13] October 2007 is the tenth month of that year. ...

In February, 2008, another different family of high temperature superconductors was discovered.^[14] Hideo Hosono of the Tokyo Institute of Technology and colleagues found that lanthanum oxygen fluorine iron arsenide (LaO_1-xF_xFeAs) becomes a superconductor at 26 kelvin. Other researchers quickly found other materials in the same family that have transition temperatures as high as 55K. Experts hope that having another family to study will simplify the task of explaining how these materials work.

Applications

Main article: Technological applications of superconductivity

Superconducting magnets are some of the most powerful electromagnets known. They are used in maglev trains, MRI and NMR machines and the beam-steering magnets used in particle accelerators. They can also be used for magnetic separation, where weakly magnetic particles are extracted from a background of less or non-magnetic particles, as in the pigment industries. Some technological innovations benefiting from the discovery of superconductivity include sensitive magnetometers based on SQUIDs, digital circuits (including those based on Josephson junctions and rapid single flux quantum technology), Magnetic Resonance Imaging, beam-steering magnets in particle accelerators, power cables, and microwave filters (e. ... Superconducting magnets are electromagnets that are built using superconducting coils. ... An electromagnet is a type of magnet in which the magnetic field is produced by the flow of an electric current. ... Transrapid at the Emsland test facility Transrapid maglev in Shanghai Magnetic levitation transport, or maglev, is a radically new form of transportation that suspends, guides and propels vehicles via electro-magnetic energy. ... MRI redirects here. ... NMR may refer to: Nuclear magnetic resonance, a phenomenon involving the interaction of atomic nuclei and external magnetic fields Nielsen Media Research, a U.S. company which measures TV, radio and newspaper audiences This is a disambiguation page — a navigational aid which lists other pages that might otherwise share the... Atom Smasher redirects here. ... Natural Ultramarine pigment in powdered form. ...

Superconductors have also been used to make digital circuits (e.g. based on the Rapid Single Flux Quantum technology) and RF and microwave filters for mobile phone base stations. Digital circuits are electric circuits based on a number of discrete voltage levels. ... In electronics, rapid single flux quantum (RSFQ) is a digital electronics technology that relies on quantum effects in superconducting materials to switch signals, instead of transistors. ... High-Temperature Superconductivity (HTS) RF and Microwave Filters operate in the cryogenic temperature range, about 77K (-196C, room temperature is about 300K). ...

Superconductors are used to build Josephson junctions which are the building blocks of SQUIDs (superconducting quantum interference devices), the most sensitive magnetometers known. Series of Josephson devices are used to define the SI volt. Depending on the particular mode of operation, a Josephson junction can be used as photon detector or as mixer. The large resistance change at the transition from the normal- to the superconducting state is used to build thermometers in cryogenic micro-calorimeter photon detectors. Josephson junctions, first postulated by B. D. Josephson and first made by John Rowell and Philip Anderson, are quantum-mechanical circuit elements of superconducting devices. ... For other uses, see Squid (disambiguation). ... A magnetometer is a scientific instrument used to measure the strength and/or direction of the magnetic field in the vicinity of the instrument. ... Josephson junction array chip developed by NIST as a standard volt. ... Josephson junctions, first postulated by B. D. Josephson and first made by John Rowell and Philip Anderson, are quantum-mechanical circuit elements of superconducting devices. ... A detector is a device that detects or measures some phenomenon or stimulus, and produces some signal in response. ... In telecommunications a mixer is a frequency mixer. ... A calorimeter is a device used for calorimetry, the science of measuring the heat of chemical reactions or physical changes as well as heat capacity. ... A detector is a device that detects or measures some phenomenon or stimulus, and produces some signal in response. ...

Other early markets are arising where the relative efficiency, size and weight advantages of devices based on HTS outweigh the additional costs involved.

Promising future applications include high-performance transformers, power storage devices, electric power transmission, electric motors (e.g. for vehicle propulsion, as in vactrains or maglev trains), magnetic levitation devices, and Fault Current Limiters. However superconductivity is sensitive to moving magnetic fields so applications that use alternating current (e.g. transformers) will be more difficult to develop than those that rely upon direct current. For other uses, see Transformer (disambiguation). ... Superconducting Magnetic Energy Storage (SMES) uses the ability of certain materials to conduct electricity without resistance (superconductivity) to store electrical power. ... Power line redirects here. ... For other kinds of motors, see motor. ... A vactrain is an exotic, as-yet-unbuilt proposal for future high-speed railroad transportation. ... Transrapid Shanghai Maglev Train stopping at terminus Longyang Road station Transrapid Shanghai Maglev Train Inside the Shanghai Transrapid maglev Inside the Shanghai Transrapid maglev VIP section Magnetic levitation transport, or maglev, is a form of transportation that suspends, guides and propels vehicles (especially trains) using electromagnetic force. ... Magnetic levitation is the process by which an object is suspended above another object with no other support but magnetic fields. ... A Fault Current Limiter (FCL) is a device which limits the prospective Fault current when a fault occurs. ... City lights viewed in a motion blurred exposure. ... Direct current (DC or continuous current) is the continuous flow of electricity through a conductor such as a wire from high to low potential. ...

References

The University of Arizona (UA or U of A) is a land-grant and space-grant public institution of higher education and research located in Tucson, Arizona, United States. ... Hagen Kleinert, Photo taken in 2006 Hagen Kleinert is Professor of Theoretical Physics at the Free University of Berlin, Germany, and Honorary Member of the Russian Academy of Creative Endeavors. ...

See also

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