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Topic: Superconductivity


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  Superconductivity - Wikipedia, the free encyclopedia
Superconductivity is a phenomenon occurring in certain materials at low temperatures, characterized by exactly zero electrical resistance and the exclusion of the interior magnetic field (the Meissner effect).
Superconductivity was discovered in 1911 by Heike Kamerlingh Onnes, who was studying the resistivity of solid mercury at cryogenic temperatures using the recently-discovered liquid helium as a refrigerant.
In 1950, the phenomenological Ginzburg-Landau theory of superconductivity was devised by Landau and Ginzburg.
en.wikipedia.org /wiki/Superconductivity   (2804 words)

  
 Superconductivity - Wikipedia
Superconductivity occurs in a wide variety of materials, including simple elements like tin and aluminum, various metallic alloys, and certain ceramic compounds containing planes of copper and oxygen atoms.
The onset of superconductivity is accompanied by abrupt abrupt changes in various physical properties, which is the hallmark of a phase transition.
Superconductivity was discovered in 1911 by Onnes, who was studying the resistivity of solid mercury at cryogenic temperatures using the recently-discovered liquid helium as a refrigerant.
wikipedia.findthelinks.com /su/Superconductivity.html   (1760 words)

  
 Superconductivity   (Site not responding. Last check: 2007-10-21)
The understanding of superconductivity was advanced in 1957 by three American physicists-John Bardeen, Leon Cooper, and John Schrieffer, through their Theories of Superconductivity, know as the BCS Theory.
Josephson discovered that if two superconducting metals were separated by a thin insulating barrier such as an oxide layer 10 to 20 angstroms thick, it is possible for electron pairs to pass through the barrier without resistance.
A large scale shift to superconductivity technology depends on whether wires can be prepared from the brittle ceramics that retain their superconductivity at 77 K while supporting large current densities.
www.rare-earth-magnets.com /magnet_university/superconductivity.htm   (4648 words)

  
 Superconductivity
A new era in the study of superconductivity began in 1986 with the discovery of high critical temperature superconductors.
The variations on barium-copper-oxide ceramics which achieved the superconducting state at much higher temperatures are often just referred to as high temperature superconductors and form a class of their own.
The superconductivity in Type I superconductors is modeled well by the BCS theory which relies upon electron pairs coupled by lattice vibration interactions.
hyperphysics.phy-astr.gsu.edu /hbase/solids/scond.html   (619 words)

  
 Superconductivity   (Site not responding. Last check: 2007-10-21)
The materials that exhibited superconductive behavior only did so if they were cooled to within a few degrees of absolute zero, which limited their use to highly specialized applications.
Interest in superconductivity skyrocketed in the late 1980s when materials were discovered that remained superconductive at relatively high temperatures, but after the initial excitement wore off, development of practical applications proved painfully slow.
There were also the problems of connecting the three-millivolt logic levels of the superconducting circuitry to conventional logic in the non-cryogenic parts of the computer, and of thermally isolating the superconducting CPU from the hot outside world, while still providing connection to low speed devices like disks and I/O interfaces.
www.vectorsite.net /ttspcon.html   (4459 words)

  
 Howstuffworks "What is superconductivity?"
Superconductivity is a phenomenon observed in several metals and ceramic materials.
Superconducting loops of wire have been shown to carry electrical currents for several years with no measurable loss.
Another property of a superconductor is that once the transition from the normal state to the superconducting state occurs, external magnetic fields can't penetrate it.
science.howstuffworks.com /question610.htm   (600 words)

  
 Hole superconductivity   (Site not responding. Last check: 2007-10-21)
Superconductivity occurs due to pairing of hole carriers, and is driven by the fact that paired holes can propagate more easily (have a smaller effective mass) than single holes.
If the theory is correct it implies that the electron-phonon interaction is irrelevant to superconductivity, that BCS theory is incorrect and that London theory is incorrect.
71) Electron-hole asymmetry and superconductivity, cond-mat/0211643, Phys.Rev.B 68, 012510 (2003).
physics.ucsd.edu /~jorge/hole.html   (1462 words)

  
 EERE: Power - Superconductivity   (Site not responding. Last check: 2007-10-21)
The capacity of superconducting materials to handle large amounts of current with no resistance and extremely low energy losses can be applied to electric devices such as motors and generators, and to electricity transmission in power lines.
A superconducting power system would meet the growing demand for electricity with fewer power plants and transmission lines than would otherwise be needed.
Superconducting materials that must be cooled to around -269°C have been used by utilities in superconducting magnetic energy storage devices that provide backup power and protect power quality.
www.eere.energy.gov /EE/power_superconductivity.html   (311 words)

  
 Superconductivity   (Site not responding. Last check: 2007-10-21)
This phenomenon was called superconductivity, and the temperature at which it occurred is called its critical temperature.
Lead is a Type I superconductor with a critical temperature of 7.2 K. Although such superconductors can conduct currents with zero resistance, their usefulness is limited because of low critical magnetic fields.
The evidence for an energy gap was one of the steps which led to the BCS theory of superconductivity.
hyperphysics.phy-astr.gsu.edu /hbase/solids/scdis.html   (275 words)

  
 Superconductivity (Science Tracer Bullet - Science Reference Services, Library of Congress)
Superconductivity is the flow of electric current without any resistance.
Superconducting applications of niobium: containing papers presented at the TMS Symposium on Niobium and Niobium Alloys in Superconducting Applications, February 24-27, 1987.
Superconductivity and band structure of BCC zirconium using the linear muffin-tin orbital method.
www.loc.gov /rr/scitech/tracer-bullets/superconducttb.html   (1314 words)

  
 Talks - Hole superconductivity   (Site not responding. Last check: 2007-10-21)
We propose that both superconductivity and ferromagnetism in metals are driven by quasiparticle 'undressing', i.e., that the correlations between quasiparticles that give rise to the collective state are associated with an increase in $z$ and a corresponding decrease in $m^*$ of the carriers.
In contrast, in conventional descriptions of superconductivity and ferromagnetism the transitions to these collective states result in $increase$ in kinetic energy of the carriers and are driven by lowering of potential energy and exchange energy respectively.
Superconductivity occurs predominantly in materials where the charge carriers in the normal state are holes rather than electrons.
physics.ucsd.edu /~jorge/talks.html   (3163 words)

  
 Superconductivity   (Site not responding. Last check: 2007-10-21)
Superconductivity is a phenomenon which occurs in certain materials and is characterized by the absence of electrical resistivity.
Properties of superconducting materials are altered locally by the presence of defects in the materials.
A fluxoid encompassing or adjacent to such a defect in the material has its energy altered and its free motion through the superconductor is inhibited.
www.americanmagnetics.com /tutorial/supercon.html   (559 words)

  
 Superconductivity
The removal of the iron teeth in the armature not only makes superconducting motors lighter (with lower inertia), it also leaves more room for armature copper, which lowers the electrical losses and also improves machine efficiency.
The temperature at which a metal becomes superconducting varies inversely as the square root of its molecular weight.
Superconductivity at 93 K in a new mixed-phase Yb-Ba-Cu-O compound system at ambient pressure.
hypertextbook.com /physics/modern/superconductivity/index.shtml   (1578 words)

  
 Superconductivity
A two-dimensional macroscopic model for superconductivity in thin films having variable thickness is derived through an averaging process across the film thickness.
A formal asymptotic expansion is used to simplify the Ginzburg-Landau model of superconductivity in the limit of large values of the Ginzburg-Landau parameter and high applied magnetic field strengths.
A model for superconductivity in thin films having variable thickness is derived through an averaging process across the film.
orion.math.iastate.edu /research/super/homepage.html   (3284 words)

  
 Ghost of Superconductivity on a Fall Day
The results reinforce other experiments suggesting that a "shadow" of the superconducting state exists even when the material appears normal and may give clues about the underlying causes of the HTS phenomenon.
When the field is applied to a superconducting sample, the vortices can't form "in place" but must shoulder their way in from the edges.
The team suggests that even at higher temperatures something resembling superconductivity may be present in small regions, as the stripes model suggests.
focus.aps.org /story/v13/st19   (669 words)

  
 Souped-up Superconductivity
Between the dots this external field cancelled the field from the dots themselves, allowing the superconductivity to switch on and the film to carry electricity without resistance.
Of course, directly under the dots, the external field reinforced the one that was already there and further suppressed the superconductivity, leaving little islands where current was inhibited.
The magnetic dots might someday be incorporated into superconducting wires to counter the fields the wires themselves produce and thus increase the amount of current they can carry, Moshchalkov says.
focus.aps.org /story/v11/st21   (630 words)

  
 Superconductivity
Superconductivity is infinitely more than a physics phenomena of the first order.
The diamagnetism of the superconducting state is extraordinary in that it expels from its interior any external magnetic field(s) -- up to a limiting critical magnetic field strength.
The critical elements in reaching the superconducting state are for conduction electrons to somehow form Cooper pairs, which then in turn automatically condense into a coherent flow, the “coherent” aspect being similar to that of a laser, i.e.
www.halexandria.org /dward156.htm   (3628 words)

  
 2004 GRC on Superconductivity
The aim of this conference is to present a forum for discussion of superconductivity in cuprates, cobaltates, alkalides, C60, actinides, borides, heavy fermion materials, etc. The conference will focus on the physical properties and materials aspects of superconductivity, such phase as diagrams, electronic structure, spectroscopic properties, to mention just a few.
The mechanisms causing superconductivity may be quite different from case to case, which is an important aspect which we seek to highlight during this conference.
We strongly encourage the participation of scientists in the initial stages of their career, by their active participation in informal discussion groups and poster sessions.
www.grc.uri.edu /programs/2004/supercon.htm   (354 words)

  
 superconductivity
Classical superconductivity (superconductivity at temperatures near absolute zero) is displayed by some metals, including zinc, magnesium, lead, gray tin, aluminum, mercury, and cadmium.
An interesting aspect of the phenomenon is the continued flow of current in a superconducting circuit after the source of current has been shut off: for example, if a lead ring is immersed in liquid helium, an electric current that is induced magnetically will continue to flow after the removal of the magnetic field.
Superconductivity glimpsed near 300 K. (superconductivity at room temperature)
www.infoplease.com /ce6/sci/A0847256.html   (472 words)

  
 Physics Encyclopedia: Superconductivity and Superfluidity
Superconductivity - site includes introduction, theories, uses, quiz etc..
Superconductivity - an article from Suite101, by J. Winkler.
High Temperature Superconductivity - cond-mat/9802202; overview of current status of research.
members.tripod.com /~IgorIvanov/physics/super.html   (130 words)

  
 Awards Process - IEEE Technical Council on Superconductivity
DESCRIPTION: The Council on Superconductivity of the Institute of Electrical and Electronics Engineers (IEEE) has established two awards, approved by the IEEE, to recognize researchers, engineers and managers, who during their professional careers, have made outstanding contributions to the field of applied superconductivity.
His office funded the majority of the programs in the US on superconducting materials and large-scale applications of superconductivity other than those funded by the Department of Energy.
The nomination letter and the letters of endorsement must be received by the Chair of the Awards Committee no later than 5 PM (local time) on 28 February of the year in which an applied superconductivity conference is held.
www.ewh.ieee.org /tc/csc/awardProcess.html   (439 words)

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