 |
|
New theory for latest high-temperature superconductors
August 14, 2008Physicists from Rice and Rutgers universities have published a new theory that explains some of the complex electronic and magnetic properties of iron "pnictides." In a series of startling discoveries this spring, pnictides were shown to superconduct at relatively high temperatures. The surprising discoveries created a great deal of excitement in the condensed matter physics community, which has been scrambling to better understand and document the unexpected results.
High-temperature superconductivity -- a phenomenon first documented in 1986 -- remains one of the great, unexplained mysteries of condensed matter physics. Until the discovery of the iron pnictides (pronounced NIK-tides), the phenomena was limited to a class of copper-based compounds called "cuprates" (pronounced COO-prayts).
The new pnictide theory appears in this week's issue of Physical Review Letters.
"There is a great deal of excitement in the quantum condensed matter community about the iron pnictides," said paper co-author Qimiao Si, Rice University theoretical physicist. "For more than 20 years, our perspective was limited to cuprates, and it is hoped that this new class of materials will help us understand the mechanism for high-temperature superconductivity."
From its initial discovery, high-temperature superconductivity came as a shock to physicists. Superconductors are materials that conduct electricity without any resistance, and in 1986, the prevailing theory of superconductivity held that the phenomenon could not occur at temperatures greater than about 30 kelvins (minus 405 degrees Fahrenheit). Some cuprates have since been discovered to superconduct at temperatures higher than 140 kelvins.
The 2006 discovery of superconductivity in one iron pnictide did not receive much notice from the physics community, since it occurred only below several kelvins. In February 2008, a group from Japan discovered superconductivity above 20 kelvins in another of the iron pnictides. In March and April, several research groups from China showed that related iron pnictides superconduct at temperatures greater than 50 kelvins.
In their new theory, Si and Rutgers University theorist Elihu Abrahams explain some of the similarities and differences between cuprates and pnictides. The arrangement of atoms in both types of materials creates a "strongly correlated electron system" in which electrons interact in a coordinated way and behave collectively.
Si and Abrahams propose that the pnictides exhibit a property called "magnetic frustration," a particular atomic arrangement that suppresses the natural tendency of iron atoms to magnetically order themselves in relation to each other. These frustration effects enhance magnetic quantum fluctuations, which may be responsible for the high-temperature superconductivity.
"Precisely how this happens is one of the challenging questions in strongly correlated electron systems," Abrahams said. "But even though we don't know the precise mechanism, we are still able to make some general predictions about the behavior of pnictides, and we've suggested a number of experiments that can test these predictions." The tests include some specific forms of the electronic spectrum and spin states.
Rice University
"There is a great deal of excitement in the quantum condensed matter community about the iron pnictides," said paper co-author Qimiao Si, Rice University theoretical physicist. "For more than 20 years, our perspective was limited to cuprates, and it is hoped that this new class of materials will help us understand the mechanism for high-temperature superconductivity."
From its initial discovery, high-temperature superconductivity came as a shock to physicists. Superconductors are materials that conduct electricity without any resistance, and in 1986, the prevailing theory of superconductivity held that the phenomenon could not occur at temperatures greater than about 30 kelvins (minus 405 degrees Fahrenheit). Some cuprates have since been discovered to superconduct at temperatures higher than 140 kelvins.
The 2006 discovery of superconductivity in one iron pnictide did not receive much notice from the physics community, since it occurred only below several kelvins. In February 2008, a group from Japan discovered superconductivity above 20 kelvins in another of the iron pnictides. In March and April, several research groups from China showed that related iron pnictides superconduct at temperatures greater than 50 kelvins.
In their new theory, Si and Rutgers University theorist Elihu Abrahams explain some of the similarities and differences between cuprates and pnictides. The arrangement of atoms in both types of materials creates a "strongly correlated electron system" in which electrons interact in a coordinated way and behave collectively.
Si and Abrahams propose that the pnictides exhibit a property called "magnetic frustration," a particular atomic arrangement that suppresses the natural tendency of iron atoms to magnetically order themselves in relation to each other. These frustration effects enhance magnetic quantum fluctuations, which may be responsible for the high-temperature superconductivity.
"Precisely how this happens is one of the challenging questions in strongly correlated electron systems," Abrahams said. "But even though we don't know the precise mechanism, we are still able to make some general predictions about the behavior of pnictides, and we've suggested a number of experiments that can test these predictions." The tests include some specific forms of the electronic spectrum and spin states.
Rice University
Superconductivity Current Events and Superconductivity News RSSOak Ridge supercomputer is the world's fastest for science
A Cray XT high-performance computing system at the Department of Energy's (DOE) Oak Ridge National Laboratory is the world's fastest supercomputer for science.
Electron pairs precede high-temperature superconductivity
Like astronomers tweaking images to gain a more detailed glimpse of distant stars, physicists at the U.S. Department of Energy's (DOE) Brookhaven National Laboratory have found ways to sharpen images of the energy spectra in high-temperature superconductors - materials that carry electrical current effortlessly when cooled below a certain temperature.
New Instrument Puts New Spin on Superconductors
Researchers at the U.S. Department of Energy's Ames Laboratory are part of collaborative team that's used a brand new instrument at the DOE's Spallation Neutron Source to probe iron-arsenic compounds, the "hottest" new find in the race to explain and develop superconducting materials.
Superconductivity can induce magnetism
When an electrical current passes through a wire it emanates heat - a principle that's found in toasters and incandescent light bulbs.
Galaxy Zoo -- an Internet superstar
Since Galaxy Zoo's launch in July 2007, some 150,000 members of the public, inspired by the opportunity to be the first to see and classify a galaxy, have helped professional astronomers via this on-line mass-participation project to carry out real scientific research.
Scientists reveal effects of quantum 'traffic jam' in high-temperature superconductors
Scientists at the U.S. Department of Energy's Brookhaven National Laboratory, in collaboration with colleagues at Cornell University, Tokyo University, the University of California, Berkeley, and the University of Colorado, have uncovered the first experimental evidence for why the transition temperature of high-temperature superconductors -- the temperature at which these materials carry electrical current with no resistance -- cannot simply be elevated by increasing the electrons' binding energy.
Creating unconventional metals
The semiconductor silicon and the ferromagnet iron are the basis for much of mankind's technology, used in everything from computers to electric motors. In this week's issue of the journal Nature (August 21st) an international group of scientists, including academic and industrial researchers from the UK, USA and Lesotho, report that they have combined these elements with a small amount of another common metal, manganese, to create a new material which is neither a magnet nor an ordinary semiconductor.
Exotic Materials Using Neptunium, Plutonium Provide Insight into Superconductivity
Physicists at Rutgers and Columbia universities have gained new insight into the origins of superconductivity - a property of metals where electrical resistance vanishes - by studying exotic chemical compounds that contain neptunium and plutonium.
Room temperature superconductivity
Scientists at the University of Cambridge have for the first time identified a key component to unravelling the mystery of room temperature superconductivity, according to a paper published in today's edition of the scientific journal Nature.
UBC physicists develop 'impossible' technique to study and develop superconductors
A team of University of British Columbia researchers has developed a technique that controls the number of electrons on the surface of high-temperature superconductors, a procedure considered impossible for the past two decades.
More Superconductivity Current Events and Superconductivity News Articles
 | Introduction to Superconductivity: Second Edition (Dover Books on Physics) by Michael Tinkham Accessible to graduate students and experimental physicists, this volume emphasizes physical arguments and minimizes theoretical formalism. Topics include the Bardeen-Cooper-Schrieffer and Ginzburg-Landau theories, magnetic properties of classic type II superconductors, the Josephson effect, fluctuation effects in classic superconductors, high-temperature superconductors, and nonequilibrium... |
 | Superconductivity by Poole Superconductivity, 2E is an encyclopedic treatment of all aspects of the subject, from classic materials to fullerenes. Emphasis is on balanced coverage, with a comprehensive reference list and significant graphicsfrom all areas of the published literature. Widely used theoretical approaches are explained in detail. Topics of special interest include high temperature superconductors,... |
 | Superconductivity Volume I (Vol. 1) by R. D. Parks |
 | Handbook of Applied Superconductivity, 2 Volume Set The Handbook of Applied Superconductivity, Two-Volume Set covers all important aspects of applied superconductivity and the supporting low-temperature technologies. The handbook clearly demonstrates the capabilities of superconducting technologies and illustrates how to implement these technologies in new areas of academic and industrial research and development. Volume One provides an... |
 | The Cold Wars: A History of Superconductivity by Jean Matricon, Charles Glashausser There is no temperature below absolute zero, and, in fact, zero itself is impossible to reach. The quest to reach it has lured scientists for several centuries revealing interesting and unexpected phenomena along the way. Atoms move more slowly at low temperatures, butmatter at barely above absolute zero is not immobile or even necessarily frozen. Among the most peculiar of matter's strange... |
 | Theory Of Superconductivity (Advanced Book Classics) by J. Robert Schrieffer Theory of Superconductivity is considered one of the best treatment of the field. This monograph, by Nobel Prize-winning physicist J. Robert Schrieffer, has been reprinted because of its enduring value as an introduction to the theory of superconductivity. The fundamentals of the theory of superconductivity are stresses as a means of providing the reader with a framework for the literature in... |
 | Theory of Nonequilibrium Superconductivity (International Series of Monographs on Physics) by Nikolai B. Kopnin This is the first text on the modern theory of superconductivity. It deals with the behavior of superconductors in external fields varying in time, and with transport phenomena in superconductors. The text starts with the fundamentals of the first-principle, microscopic theory of superconductivity, and guides the reader through the modern theoretical analysis to applications of the theory to... |
 | Superfluidity and Superconductivity (Graduate Student Series in Physics) by D.R. Tilley, J Tilley Superfluidity and Superconductivity, Third Edition introduces the low-temperature phenomena of superfluidity and superconductivity from a unified viewpoint. The book stresses the existence of a macroscopic wave function as a central principle, presents an extensive discussion of macroscopic theories, and includes full descriptions of relevant experimental results throughout. This edition also... |
 | Superconductivity by V. L. Ginzburg, E. A. Andryushin What is superconductivity? How was it discovered? What are the properties of superconductors, how are they applied now, and how are they likely to become widely used in the near future? These are just some of the questions which this important book sets out to answer. Starting with the discovery of superconductivity over ninety years ago, the book guides the readers through the many years of... |
 | Superconductivity, Superfluids, and Condensates (Oxford Master Series in Condensed Matter Physics) by James F. Annett Superconductivity, provides a basic introduction to one of the most innovative areas in condensed matter physics today. This book includes ample tutorial material, including illustrations, chapter summaries, graded problem sets, and concise examples. This book is part of the Oxford Master Series in Condensed Matter... |
| © 2008 BrightSurf.com |