'Cooper pairs' can be found in insulators as well superconductors
November 22, 2007Nearly a century ago, Dutch physicist Kamerlingh Onnes discovered that some metals transform into perfect electrical conductors when cooled to temperatures near absolute zero. Once started, their currents of electrons can flow perpetually.
How electrons reorganize to produce this behavior remained mysterious until 1957, when theoretical physicists John Bardeen, Leon Cooper and Robert Schrieffer unveiled their BCS (Bardeen, Cooper, Schrieffer) theory of superconductivity. The theory shows that superconducting electrons form pairs, now known as Cooper pairs, that correlate their motion with other electron pairs to smoothly and infinitely flow. Cooper, currently the Thomas J. Watson, Sr. Professor of Science at Brown University, went on with his colleagues to win a Nobel Prize for this work.
Now, in the 50th anniversary year of BCS theory, Brown physicists are making a surprising addi-tion to the scientific canon created by their famous colleague. In new work appearing in Science, the team shows that Cooper pairs not only form in superconductors, but can also form their opposite – electrical insulators.
“Our finding is quite counterintuitive,” said James Valles, a Brown professor of physics who led the research. “Cooper pairing is not only responsible for conducting electricity with zero resis-tance, but it can also be responsible for blocking the flow of electricity altogether.”
Michael Stewart is a physics graduate student at Brown and the lead author of the Science article. Stewart started the research as a skeptic. He’d seen scientific papers suggesting that Cooper pairs might exist in electrical insulators under certain conditions. Stewart decided to test this unorthodox idea. “I’d would’ve put my money down,” he said, “that the answer was ‘no’.”
To create an insulator for his experiments, Stewart chose bismuth, a rare metal that, when thick, serves as an excellent superconductor and, when thin, serves as an exceptional insulator. Stewart turned to Jimmy Xu, a Brown professor of engineering and physics and a pioneering nanotechnology researcher, to create a template for the special experimental film.
Xu supplied a template honeycombed with holes measuring only 50 nanometers in diameter. When coated with an ultra-thin coating of bismuth just four atoms thick, and cooled to super-low temperatures, the material could be transformed into either a superconductor to insulator. When the material was behaving as an insulator, and the researchers applied a magnetic field, they detected a telltale change in electrical current, which announced the presence of Cooper pairs.
While the team found that Cooper pairs are present in both superconductors and insulators, they believe that they behave differently in each instance. In superconductors, pairs link up with other pairs and move in a linear way to create a continuous stream of electric current. Think of a conga line. But in the insulating film, researchers believe the pairs spin solo. Think of couples twirling on a ballroom dance floor.
The holes in their test material were the clincher, Valles and Stewart said, allowing them to detect the electron pairs. “Cooper pairs formed, but stayed segregated in these whirlpools,” Stewart said. “Because of that, the pairs can’t make a continuous line of current.”
The findings could help researchers understand the limits of superconductivity and, perhaps, push them to create insulated wires that conduct electricity without heating up. Cooper said the work sheds important and intriguing new light on quantum effects.
“This very interesting result reminds us that unexpected, important discoveries await if we continue to look," Cooper said.
Source: Brown University
-
Brown physicist discovers odd, fluctuating magnetic waves
Feb 23, 2010 |
4.8 / 5 (21) |
7
-
Watching a gas turn superfluid
Jan 18, 2012 |
4.8 / 5 (8) |
5
-
Woodsmoke from cooking fires linked to pneumonia, cognitive impacts
Nov 10, 2011 |
2 / 5 (2) |
1
-
Superconductivity's third side unmasked
Jun 17, 2011 |
4.8 / 5 (15) |
42
-
The curious case of germanium-72: An unusual isotope changes phases as temperature rises
Jun 02, 2011 |
4.9 / 5 (9) |
5
-
Engineers build first sub-10-nm carbon nanotube transistor
Feb 01, 2012 |
4.9 / 5 (31) |
30
-
Something old, something new: Evolution and the structural divergence of duplicate genes
Jan 31, 2012 |
4.6 / 5 (7) |
1
-
The hidden nanoworld of ice crystals: Revealing the dynamic behavior of quasi-liquid layers
Jan 30, 2012 |
5 / 5 (3) |
1
-
Stock market network reveals investor clustering
Jan 27, 2012 |
3.9 / 5 (23) |
8
-
Of microchemistry and molecules: Electronic microfluidic device synthesizes biocompatible probes
Jan 26, 2012 |
5 / 5 (1) |
0
-
Books To Inspire a Beginnig Physics Student
1 hour ago
-
Pith balls problem
1 hour ago
-
Electrostatics
1 hour ago
-
what is phase constant
1 hour ago
-
Basics In electromagnetic wave
1 hour ago
-
How to calculate theoretical initial velocity?
2 hours ago
- More from Physics Forums - General Physics
More news stories
Putting the squeeze on planets outside our solar system
(PhysOrg.com) -- Using high-powered lasers, scientists at Lawrence Livermore National Laboratory and collaborators discovered that molten magnesium silicate undergoes a phase change in the liquid state, abruptly ...
12 hours ago |
4.3 / 5 (7) |
0
|
Hovering not hard if you're top-heavy, researchers find
Top-heavy structures are more likely to maintain their balance while hovering in the air than are those that bear a lower center of gravity, researchers at New York University's Courant Institute of Mathematical Sciences ...
13 hours ago |
5 / 5 (1) |
1
|
SLAC, Stanford team focuses on high-energy electrons to treat cancer
Accelerator physicists at SLAC and cancer specialists from Stanford are working on a new technology that could dramatically reduce the time needed for cancer radiation treatments. The team ran an initial experiment ...
16 hours ago |
5 / 5 (2) |
0
Measurements from high-energy collisions lead to better understanding of why meson particles disappear
For several years, physicists at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory (BNL), USA, have studied an unusual state of matter called the quarkgluon plasma, which they ...
17 hours ago |
4.5 / 5 (4) |
0
Explained: Sigma
It's a question that arises with virtually every major new finding in science or medicine: What makes a result reliable enough to be taken seriously? The answer has to do with statistical significance -- but ...
Feb 09, 2012 |
5 / 5 (16) |
53
Anonymous knocks CIA website offline (Update)
The website of the Central Intelligence Agency was inaccessible on Friday after the hacker group Anonymous claimed to have knocked it offline.
Google users warned of threat to smartphone wallets
Users of Google smartphone wallets were being warned on Friday that there is a way to crack pass codes intended to thwart thieves from going on illicit shopping sprees.
New error-correcting codes guarantee the fastest possible rate of data transmission
Error-correcting codes are one of the triumphs of the digital age. Theyre a way of encoding information so that it can be transmitted across a communication channel such as an optical fiber o ...
Humans may have helped the decline of African rainforests 3000 years ago
(PhysOrg.com) -- Large areas of rainforests in Central Africa mysteriously disappeared over three thousand years ago, to be replaced by savannas. The prevailing theory has been that the cause was a change ...
New power source discovered
(PhysOrg.com) -- Researchers at the Massachusetts Institute of Technology (MIT) and RMIT University have made a breakthrough in energy storage and power generation.
Small modular reactor design could be a 'SUPERSTAR'
(PhysOrg.com) -- Though most of today's nuclear reactors are cooled by water, we've long known that there are alternatives; in fact, the world's first nuclear-powered electricity in 1951 came from a reactor ...
Nov 22, 2007
Rank: 1 / 5 (2)
Nov 22, 2007
Rank: 1 / 5 (2)
Nov 23, 2007
Rank: 1 / 5 (1)
Nov 23, 2007
Rank: 4 / 5 (1)
Nov 28, 2007
Rank: not rated yet