|
MIT reveals superconducting surprise
February 13, 2008A better understanding of material could bring 'endless applications'
CAMBRIDGE, Mass.--MIT physicists have taken a step toward understanding the puzzling nature of high-temperature superconductors, materials that conduct electricity with no resistance at temperatures well above absolute zero.
If superconductors could be made to work at temperatures as high as room temperature, they could have potentially limitless applications. But first, scientists need to learn much more about how such materials work.
Using a new method, the MIT team made a surprising discovery that may overturn theories about the state of matter in which superconducting materials exist just before they start to superconduct. The findings are reported in the February issue of Nature Physics.
Understanding high-temperature superconductors is one of the biggest challenges in physics today, according to Eric Hudson, MIT assistant professor of physics and senior author of the paper.
Most superconductors only superconduct at temperatures near absolute zero, but about 20 years ago, it was discovered that some ceramics can superconduct at higher temperatures (but usually still below 100 Kelvin, or -173 Celsius).
Such high-temperature superconductors are now beginning to be used for many applications, including cell-phone base stations and a demo magnetic-levitation train. But their potential applications could be much broader.
"If you could make superconductors work at room temperature, then the applications are endless," said Hudson.
Superconductors are superior to ordinary metal conductors such as copper because current doesn't lose energy as wasteful heat as it flows through them, thus allowing larger current densities. Once a current is set in motion in a closed loop of superconducting material, it will flow forever.
In the Nature Physics study, the MIT researchers looked at a state of matter that superconductors inhabit just above the temperature at which they start to superconduct.
When a material is in a superconducting state, all electrons are at the same energy level. The range of surrounding, unavailable electron energy levels is called the superconducting gap. It is a critical component of superconduction, because it prevents electrons from scattering, thus eliminating resistance and allowing the unimpeded flow of current.
Just above the transition temperature when a material starts to superconduct, it exists in a state called the pseudogap. This state of matter is not at all well understood, said Hudson.
The researchers decided to investigate the nature of the pseudogap state by studying the properties of electron states that were believed to be defined by the characteristics of superconductors: the states surrounding impurities in the material.
It had already been shown that natural impurities in a superconducting material, such as a missing or replaced atom, allow electrons to reach energy levels that are normally within the superconducting gap, so they can scatter. This can be observed using scanning tunneling microscopy (STM).
The new MIT study shows that scattering by impurities occurs when a material is in the pseudogap state as well as the superconducting state. That finding challenges the theory that the pseudogap is only a precursor state to the superconductive state, and offers evidence that the two states may coexist.
This method of comparing the pseudogap and superconducting state using STM could help physicists understand why certain materials are able to superconduct at such relatively high temperatures, said Hudson.
"Trying to understand what the pseudogap state is is a major outstanding question," he said.
Massachusetts Institute of Technology
Using a new method, the MIT team made a surprising discovery that may overturn theories about the state of matter in which superconducting materials exist just before they start to superconduct. The findings are reported in the February issue of Nature Physics.
Understanding high-temperature superconductors is one of the biggest challenges in physics today, according to Eric Hudson, MIT assistant professor of physics and senior author of the paper.
Most superconductors only superconduct at temperatures near absolute zero, but about 20 years ago, it was discovered that some ceramics can superconduct at higher temperatures (but usually still below 100 Kelvin, or -173 Celsius).
Such high-temperature superconductors are now beginning to be used for many applications, including cell-phone base stations and a demo magnetic-levitation train. But their potential applications could be much broader.
"If you could make superconductors work at room temperature, then the applications are endless," said Hudson.
Superconductors are superior to ordinary metal conductors such as copper because current doesn't lose energy as wasteful heat as it flows through them, thus allowing larger current densities. Once a current is set in motion in a closed loop of superconducting material, it will flow forever.
In the Nature Physics study, the MIT researchers looked at a state of matter that superconductors inhabit just above the temperature at which they start to superconduct.
When a material is in a superconducting state, all electrons are at the same energy level. The range of surrounding, unavailable electron energy levels is called the superconducting gap. It is a critical component of superconduction, because it prevents electrons from scattering, thus eliminating resistance and allowing the unimpeded flow of current.
Just above the transition temperature when a material starts to superconduct, it exists in a state called the pseudogap. This state of matter is not at all well understood, said Hudson.
The researchers decided to investigate the nature of the pseudogap state by studying the properties of electron states that were believed to be defined by the characteristics of superconductors: the states surrounding impurities in the material.
It had already been shown that natural impurities in a superconducting material, such as a missing or replaced atom, allow electrons to reach energy levels that are normally within the superconducting gap, so they can scatter. This can be observed using scanning tunneling microscopy (STM).
The new MIT study shows that scattering by impurities occurs when a material is in the pseudogap state as well as the superconducting state. That finding challenges the theory that the pseudogap is only a precursor state to the superconductive state, and offers evidence that the two states may coexist.
This method of comparing the pseudogap and superconducting state using STM could help physicists understand why certain materials are able to superconduct at such relatively high temperatures, said Hudson.
"Trying to understand what the pseudogap state is is a major outstanding question," he said.
Massachusetts Institute of Technology
Superconductors News and Current Superconductors Events RSSUBC 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.
New superconductors present new mysteries, possibilities
Johns Hopkins University researchers and colleagues in China have unlocked some of the secrets of newly discovered iron-based high-temperature superconductors, research that could result in the design of better superconductors for use in industry, medicine, transportation and energy generation.
Powerful superconductor is in a class all its own
Superconductivity has perplexed, astounded and inspired scientists ever since it was discovered in 1911. Now, in the latest of a century of surprises, researchers at the National High Magnetic Field Laboratory at Florida State University have discovered unusual properties in a novel superconducting material that point to an entirely new kind of superconductor.
New iron-based and copper-oxide high-temperature
In the initial studies of a new class of high-temperature superconductors discovered earlier this year, research at the Commerce Department's National Institute of Standards and Technology (NIST) has revealed that new iron-based superconductors share similar unusual magnetic properties with previously known superconducting copper-oxide materials.
Superconductors get a boost from pressure
Superconductors can convey more than 150 times more electricity than copper wires because they don't restrict electron movement, the essence of electricity.
Newly discovered 'superinsulators' promise to transform materials research, electronics design
Superinsulation may sound like a marketing gimmick for a drafty attic or winter coat. But it is actually a newly discovered fundamental state of matter created by scientists at the U.S. Department of Energy's Argonne National Laboratory in collaboration with several European institutions.
The future of computing -- carbon nanotubes and superconductors to replace the silicon chip
The future of computing is under the spotlight at the Institute of Physics' Condensed Matter and Materials Physics conference at the Royal Holloway College of the University of London on 26-28 March.
New understanding for superconductivity at high temperatures
An international research team has discovered that a magnetic field can interact with the electrons in a superconductor in ways never before observed.
UT-ORNL researchers take step toward understanding superconductivity
A research group at the University of Tennessee and Oak Ridge National Laboratory led by physics professor Pengcheng Dai, along with collaborators at Boston College, has taken a step toward understanding a great physical mystery.
The quest for a new class of superconductors
Fifty years after the Nobel-prize winning explanation of how superconductors work, a research team from Los Alamos National Laboratory, the University of Edinburgh and Cambridge University are suggesting another mechanism for the still-mysterious phenomenon.
More Superconductors News Articles
| © 2008 BrightSurf.com |