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Topic: High temperature superconductors

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	08.16.2004 - Vibrations in crystal lattice plays big role in high temperature superconductors
		High temperature superconductors are almost always some type of copper oxide (cuprate) ceramic doped with a variety of elements, from bismuth, yttrium and lanthanum to strontium and calcium.
		The complex crystal structure of Bi-2212, a typical cuprate ceramic high temperature superconductor, showing two distinct alternating layers: the copper oxide layer (purple is copper, brown is oxygen) and the bismuth oxide layer (green is bismuth), interspersed with atoms of calcium (pink) and strontium (orange).
		According to many of these theories, high temperature superconductivity arises from quantum voids or "holes," which are created by depleting electrons from the sample, moving on top of a background of magnetic moments.
	www.berkeley.edu /news/media/releases/2004/08/16_Lanzara.shtml (1185 words)

	High Temperature Superconductors
		Its critical temperature of 30 K was the highest which had been measured to date, but their discovery started a surge of activity which discovered superconducting behavior as high as 125 K. Click on any of the compound formuli for further details.
		Illustrative of the complexity of the high-temperature superconductor materials is this phase diagram which applies to the cuprate materials.
		The high temperature superconductors are ceramic materials with layers of copper-oxide spaced by layers containing barium and other atoms.
	hyperphysics.phy-astr.gsu.edu /hbase/solids/hitc.html (358 words)

	High Temperature Superconductors (Site not responding. Last check: 2007-10-07)
		Its critical temperature of 30 K was the highest which had been measured to date, but their discovery started a surge of activity which discovered superconducting behavior as high as 125 K. Click on any of the compound formuli for further details.
		high temperature superconductors are ceramic materials with layers of copper-oxide spaced by layers containing barium and other atoms.
		The yttrium compound is often called the 1-2-3 superconductor because of the ratios of its constituents.
	sina.sharif.edu /~varahram/hts-course/hitc.htm (313 words)

	Superconductivity: High Temperature Superconductivity
		The general view point (determined by "majority vote") seems to be that low temperature superconductors are phonon mediated whereas high Tc ones are somehow "unconventional" and anisotropic, although the origin of the anisotropy remains controversial.
		Discovered in 1987, high temperature superconductivity in the copper oxide ceramics continues to be the most nettling problems in modern solid state physics.
		The complexity and difficulties with high temperature superconductivity is well illustrated by the Buddhist parable of the blind men trying to describe “experimentally” an elephant.
	www.lycos.com /info/superconductivity--high-temperature-superconductivity.html (755 words)

	Applications of high temperature superconductors
		Other important superconductor properties were discovered during the course of the last century, such as the exclusion of magnetic flux lines (the Meissner effect), which is responsible for magnetic levitation, as shown in Fig.
		Below the critical temperature the bosons in a superconductor can all gather together in the lowest possible energy state to form the condensate, and the greater the number that have accumulated, the harder it is for one of them to leave.
		The critical temperature is 39 K, but research on this compound has just begun, and it is not clear whether it is simply an LTS type II superconductor with an unusually high critical temperature or represents a whole new superconductor family.
	www.europhysicsnews.com /full/09/article2/article2.html (3508 words)

	"High-Temperature Superconductors" by Edward Willett
		Superconductors repel magnetic fields—and can also be used to make super-powerful magnets.
		Superconductors in the special track repel superconductor-based magnets in the train, making the train actually float above the surface of the track.
		In 1962 Brian D. Josephson of England predicted that if two superconductors were brought close toegther but not allowed to touch, electrons could jump the gap and current could flow as if the two conductors were touching.
	www.edwardwillett.com /Columns/hightempsuperconductors.htm (742 words)

	High-temperature superconductivity - Wikipedia, the free encyclopedia
		High-temperature superconductors are generally considered to be those that demonstrate superconductivity at or above the temperature of liquid nitrogen, or −196 °C (77 K), since this is the most easily attainable cryogenic temperature.
		A "high-temperature" superconductor levitates a magnet (with boiling liquid nitrogen underneath) demonstrating the Meissner effect, one of the hallmark properties of superconductivity.
		Their discovery of the first high-temperature superconductor LBCO, with a transition temperature of 35 K, generated much excitement because it was previously widely assumed to be impossible for superconductivity to occur at such "high" temperatures.
	en.wikipedia.org /wiki/High-temperature_superconductor (472 words)

	Physics Research: High Temperature Superconductors
		When a current is applied to a type II superconductor (blue rectangular box) in the mixed state, the magnetic vortices (blue cylinders) feel a force (Lorentz force) that pushes the vortices at right angles to the current flow.
		However, within the family of high-temperature superconductors, the vortices have been found to be capable of forming a number of exotic new phases of matter besides the triangular lattice.
		The weak pinning of the flux lines of high-temperature superconductors gives rise to energy dissipation in these materials at finite currents, which limits the maximum value of the critical current (the current required to destroy superconductivity) and, hence, a variety of applications of the high-temperature superconductors.
	phys.kent.edu /pages/cep.htm (489 words)

	PR-BNL-07-3
		As a material becomes a superconductor, some of the holes lower their energy by falling into a superconducting state that allows them to flow without resistance.
		Superconductors also have energy gaps, but in the cuprates these gaps have different energies in different directions with respect to the copper-oxygen chemical bonds.
		Achieving this high barium concentration is extremely difficult and is the reason many scientists previously opted to use different but related materials for their research on superconducting stripes and other properties, Gu said.
	www.lightsources.org /cms/?pid=1001990 (1296 words)

	High Temperature Superconductivity (Site not responding. Last check: 2007-10-07)
		The complexity and difficulties with high temperature superconductivity is well illustrated by the Buddhist parable of the blind men trying to describe “experimentally” an elephant.
		Much of the research in High Tc superconductivity has spilled over to other areas of research where complex materials play an important role such as magnetism in the manganites, complex oxides, two and one dimensional magnets, etc. Applications could greatly benefit from the discovery of new superconductors which are more robust and allow easier manufacturing.
		The general view point (determined by "majority vote") seems to be that low temperature superconductors are phonon mediated whereas high Tc ones are somehow "unconventional" and anisotropic, although the origin of the anisotropy remains controversial.
	www-physics.ucsd.edu /~iksgrp/HighTemp.html (1807 words)

	Making High-Temperature Superconductors
		If the temperature sensor in your furnace is at the same level as the material being fired, the maximum indicated temperature should never be allowed to exceed 980 degrees Celsius.
		If the sensor for the temperature indicator is high in the chamber, the actual temperature at the bottom of the chamber may be much cooler.
		With superconductors made with the techniques described here, we have levitiated 1" neodymium bar magnets and 1/2" neodymium disk magnets, sometimes getting a levitation that was barely noticeable, and other times getting a levitation that was quite spectacular.
	www.webcom.com /cfsc/scpart1.html (4396 words)

	Are Superconductors the Future? - Chapter 5 - High Temperature Superconductors
		If there were room temperature superconductors we could replace the conductors in our homes and cities with superconductors, thus saving billions of dollars.
		High temperature superconductivity began in 1986 when Johannes Georg Bednorz and Karl Alexander Müller in IBM Research Laboratories in Zurich, Switzerland discovered a compound of barium, lanthanum, copper, and oxygen superconductor.
		1-2-3 superconductor for its relative atomic proportions of yttrium, barium, and copper.
	www.eapen.com /jacob/superconductors/chapter5.html (523 words)

	New insights into high-temperature superconductors
		In this study, we found that by substituting oxygen-16 with its heavier sibling oxygen-18, the transition temperature changes; such a substitution is known as the isotope effect.
		Superconducting materials can achieve their maximum transition temperatures at a specific amount of "doping," which is simply the addition of charged particles (negatively charged electrons or positively charged holes).
		For optimally doped materials, the higher the maximum transition temperature is, the smaller the isotope effect is.
	www.eurekalert.org /pub_releases/2007-02/ci-nii022307.php (618 words)

	HIGH TEMPERATURE SUPERCONDUCTORS: III: YBCO Conductor Development
		The high resistivity of YBCO grain boundaries is mainly attributed to the presence of solidified liquid phase and cracks at these boundaries.
		These results indicate that the high angle grain boundaries in these bars are capable of sustaining very large currents and therefore make them suitable for applications such as current leads and current limiters.
		To improve commercial confidence in high temperature superconductivity, it is imperative that superconductors are produced and tested in certain applications.
	www.tms.org /Meetings/Annual-97/Program/Sessions/TA315A.html (1692 words)

	High Temperature Superconductors
		Other superconductors, known as Type II superconductors, have a temperature range in which they are superconducting, but do not display the Meissner effect.
		The low temperature superconductors were, as far as I’ve discovered, all compounds of relatively non-magnetic elements such as aluminum, lead, or nitrogen.
		Because Type II superconductors do not completely expel magnetic flux from their interiors, the superconductivity of a Type II superconductor can actually be turned on and off by the introduction or removal of a magnetic field of sufficient strength.
	members.cox.net /kjk176/Supers.html (4746 words)

	NRL - Raman Spectroscopy of High-Temperature Superconductors
		Rising temperature, which accelerates electrons and shakes the crystal lattice through which they flow, tends to separate, or "break" pairs.
		Through extensive study on hole-doped cuprates, a consensus has been reached in the research community that the carriers that pair in hightemperature superconductors are not only very strongly coupled, but that they possess a certain angular momentum as well, making them "d-wave" superconductors.
		Adding the electron-doped cuprates to the class of dwave superconductors allows the research community to focus on possible mechanisms for d-wave pairing and why this leads to such high critical temperatures.
	www.nrl.navy.mil /content.php?P=02REVIEW157 (971 words)

	Superconductivity - Wikipedia, the free encyclopedia
		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.
		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.
		Superconductors are used to make some of the most powerful electromagnets known to man, including those used in MRI machines and the beam-steering magnets used in particle accelerators.
	en.wikipedia.org /wiki/Superconductivity (2917 words)

	High-Temperature Superconductors
		This work has led to a hypothesis for the ideal structure for a high-temperature superconductor and has revealed new aspects of the chemistry that are a reflection of the novel underlying physics of these materials.
		A characteristic feature of the high-temperature layered copper-oxide superconductors is the existence of a chemical composition that gives a maximum superconducting transition temperature, Tc, bounded below and above by the so-called under-doped and over-doped regimes.
		Thus, the observation of a maximum in the buckling at the maximum Tc indicates that, as the composition (and hence doping) is changed to increase Tc, there is a structural response that competes with superconductivity.
	www.msd.anl.gov /groups/nxrs/overview/high_temp_superconductors.html (435 words)

	New insights into high-temperature superconductors
		The results also suggest that vibrations (called phonons), within the lattice structure of these materials, are essential to their superconductivity by binding electrons in pairs.
		The early conventional superconductors had to be cooled to extremely low (below 20 K or —253ºC) temperatures for electricity to flow freely.
		The study also revealed what might be happening to modify the electronic structures among various optimally doped materials to cause the variation of the superconducting properties.
	www.innovations-report.de /html/berichte/materialwissenschaften/bericht-79791.html (548 words)

	One Mystery of High-Tc Superconductivity Solved
		In conventional superconductors, which operate at much lower temperatures (near absolute zero), superconductivity occurs as soon as electron pairs are formed.
		Because of their higher operating temperatures (up to 134 kelvins at ambient pressure and up to 164 K under high pressure), high-Tc superconductors have much greater potential for real world applications, such as zero-loss power transmission lines, than do conventional superconductors.
		Yet despite the fact that this material, at this ratio, is not a superconductor, it has a very similar energy signature -- including the energy gap in the electronic spectrum (pseudogap) -- as other high-Tc superconductors in their superconducting states.
	www.photonics.com /content/news/2006/November/20/85129.aspx (667 words)

	Argonne's superconductor research continues to lead
		Their high economic potential generated an international race among Germany, Japan and the United States to develop and market long lengths of practical wire from high-temperature superconductors.
		Argonne led a national survey to assess the potential economic impact of high-temperature superconductors in fields such as electrical power generation and transmission, electrical motors, computers and other electronic devices, magnetic energy storage, transportation, and medical diagnosis.
		Even before the discovery of high-temperature superconductors, Argonne was a world leader in studying and using low-temperature superconductors-- materials that must be cooled by liquid helium to nearly absolute zero before they conduct electricity without energy loss.
	www.anl.gov /Media_Center/News/History/news960728.html (776 words)

	#9623306 - Vortex Dynamics in Organic and High Temperature Superconductors
		Second, interlayer transport measurements will be performed to correlate with a magnetic transparent state observed in the neodymium-cerium based superconductors as well as the thallium based ones to test the model of the Josephson decoupling between the superconducting layers.
		Understanding of the vortex dynamics in the layered superconductors is important for its industrial applications, it is also interesting in terms of fundamental physics.
		The high transition temperature and the layered structure introduce new features in the behavior of quantum vortices in the mixed state.
	www.physics.miami.edu /~zuo/9623306.htm (457 words)

	02.16.00 - First-ever images of atom-scale electron clouds in high-temperature superconductors could help in design of ...
		High-temperature superconductors are materials that conduct electricity perfectly at temperatures substantially above absolute zero, that is, at 87 degrees above absolute zero (-300°F) instead of 4 degrees above zero (-452°F), the temperature at which normal superconductors operate.
		This superconductor is made up of a repeating series of layers: two bismuth oxide layers, a strontium oxide layer, and two copper oxide layers with some calcium atoms sandwiched between them.
		Cooper pairs in high temperature superconductors are thought to be formed from electrons on two adjacent copper atoms, whereas in other superconductors electrons forming a Cooper pair are often separated by thousands of atoms.
	www.berkeley.edu /news/media/releases/2000/02/02-16-2000.html (1088 words)

	Introduction to High Temperature Superconductors - a PDH Online Course for Engineers
		In this 1 PDH course, the student will be introduced to the fundamental properties of superconductors, the basics of high temperature superconductors, the Meissner effect, the zero resistance effect, practical experimentation kits, how to make a superconductor from scratch, applications for superconductors, and superconductor patent information.
		In this course, the student will be introduced to the fundamental properties of superconductors, the basics of high temperature superconductors, the Meissner effect, the zero resistance effect, practical experimentation kits, how to make a superconductor from scratch, applications for superconductors, and superconductor patent information.
		If higher temperature superconductors can be developed, it has the potential to change the world into the science fiction representation we often see in the movies (floating cars, trains, furniture, etc).
	www.pdhonline.org /courses/e168/e168.htm (548 words)

	EETimes.com - Magnetic resonance tied to superconduction (Site not responding. Last check: 2007-10-07)
		According to a team from Oak Ridge National Laboratory and the University of Tennessee, the reason these materials superconduct at such high temperatures may be a magnetic resonance that causes their anti-ferromagnetic lattice to oscillate opposing-spin orientations in synchronization with the opposing-spin orientations of the so-called Cooper pairs passing through the superconductor's molecular lattice.
		Since the discovery of a high-temperature superconductor (bismuth strontium calcium copper oxide, for which IBM received a Nobel Prize in 1987), researchers have been trying to understand why these materials superconduct at such a high temperature, in hopes of designing materials that superconduct at even higher ones.
		This commonality led the researchers to postulate a universal law governing all high-temperature materials: that their magnetic-resonance energy is proportional to their superconductivity transition temperature, suggesting that magnetic resonance in high-temperature superconductors serves the same function as phonon-lattice vibrations in low-temperature superconductors.
	www.eetimes.com /showArticle.jhtml?articleID=190302307 (1210 words)

	HIGH TEMPERATURE SUPERCONDUCTORS: IV: BSCCO and TBCCO Conductor Development
		The wind-and-react technique suffers from poor temperature control due to the coil thermal mass and the sensitivity of the superconductor to the peak temperature and cooling rates.
		This was achieved by reducing the enclosed voids in the materials under the pressure at high temperature.
		In addition of high mass density, texture structure in the superconductors has also been improved by hot compressing which in turn increased critical current of both materials.
	www.tms.org /Meetings/Annual-97/Program/Sessions/TP315A.html (1802 words)

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