(Press-News.org) CHAMPAIGN, Ill. -- University of Illinois physicists have experimentally demonstrated for the first time how three-dimensional conduction is affected by the defects that plague materials. Understanding these effects is important for many electronics applications.
Led by physics professor Brian DeMarco, the researchers achieved complete localization of quantum matter waves in three dimensions, first theorized roughly half a century ago. The group published its findings in the Oct. 7 issue of the journal Science.
Defects in materials are inevitable, but their effects are poorly understood. Understanding how disorder in a material affects waves traveling through it has implications for many applications, including ultrasonic waves in medical imaging, lasers for imaging and sensing, and electron waves for electronics and superconductors.
"The physics behind disorder is fundamental to understanding the impact of unavoidable material imperfections on these kinds of applications," DeMarco said.
Scientists have long theorized, but never observed, that strong disorder causing interference on all sides can trap a matter wave in one place, a phenomenon known as Anderson localization.
According to DeMarco, this is analogous to a trumpeter playing in a concert hall filled with randomly placed barriers that reflect sound waves. Instead of traveling in all directions, the sound stays at its source, never propagating outward because of destructive interference.
"The result? Perfect silence everywhere in the concert hall. The trumpeter blows into his instrument, but the sound never leaves the trumpet," DeMarco said. "That's exactly the case in our experiment, although we use quantum matter waves instead of sound, and the barriers are created using a speckled green laser beam."
To simulate electrons moving in waves through a metal, DeMarco's group uses ultra-cold atoms moving as matter waves in a disordered laser beam. Using laser light as an analogy for a material allows the researchers to completely characterize and control the disorder – a feat impossible in solids, which has made understanding and testing theories of Anderson localization difficult.
The researchers demonstrated that the laser light could completely localize the atoms – the first direct observation of three-dimensional Anderson localization of matter.
"This means that we can study Anderson localization in a way that is relevant to materials," DeMarco said. "Now, theories of Anderson localization in 3-D can be compared to our 'material' and tested for the first time."
VIDEO:
The impact of disorder on waves depends strongly on their energy in three dimensions. The high-energy red wave can freely propagate outward through the disordered green laser light, but the...
Click here for more information.
The team also measured the energy a particle needs to escape localization, known as the mobility edge. Waves with energy higher than the mobility edge are free to propagate throughout the disorder, but waves with energy lower than the mobility edge are completely localized - even when there is a path through the barriers.
By tuning the power of the speckled green laser beam, the researchers measured the relationship between the mobility edge and disorder strength. They found that as disorder increased, so did the mobility edge, meaning that materials with high concentrations of defects induce more localization.
DeMarco hopes to use the quantum-matter analogues to better understand and manipulate materials.
Eventually, he plans to use his measurements of Anderson localization and the mobility edge along with future work exploring other parameters to engineer materials to better perform specific applications - in particular, high-temperature superconductors.
"Comparing measurements on a solid to theory are complicated by our lack of knowledge of the disorder in the solid and our inability to remove it," DeMarco said. "But, that's exactly what we can do with our experiment, and what makes it so powerful and exciting."
INFORMATION:
The Defense Advanced Research Projects Agency, the Office of Naval Research and the National Science Foundation supported this work.
Editor's note: To contact Brian DeMarco, call 217-244-9848; email bdemarco@illinois.edu.
The paper, "Three-Dimensional Anderson Localization of Ultracold
Matter," is available online at http://www.sciencemag.org/content/334/6052/66.full.
Physicists localize 3-D matter waves for first time
2011-10-10
[Attachments] See images for this press release:
ELSE PRESS RELEASES FROM THIS DATE:
Viaden Gaming Releases New Version of Casino Software
2011-10-10
Viaden Gaming Ltd., one of the premier online casino software developers announced the updated online casino release with feature-rich functionality, new payment options and multiple usability improvements. Here are the major updates that are pushed live with the new version:
Featured Games
To enable the operators to promote the hottest and newest games, the recent online casino solution involves the 'Featured Games' option. From now on the players visiting the web-site will have the opportunity to quickly access the games recommended by the casino.
User Analytics ...
Social Security: Welfare for the Lazy or Dignity for the Disabled?
2011-10-10
You already know what we're going to say. We're Social Security Disability lawyers. Our clients, New Yorkers from the Finger Lakes region and elsewhere throughout the state, know who we are.
And not a single one of them is lazy.
Not a single one of them would call their disability benefits a welfare check.
Not a single one of them would consider what they have already earned to be an "entitlement."
Earned Wages in Exchange for Labor
The state of New York subscribes to "at-will" employment, as do most (if not all) states, which means ...
Study shows how bookmarking genes pre-cell division hastens their subsequent reactivation
2011-10-10
Cold Spring Harbor, N.Y. – In order for cells of different types to maintain their identities even after repeated rounds of cell division, each cell must "remember" which genes were active before division and pass along that memory to its daughter cells. Cells deal with this challenge by deploying a "bookmarking" process. In the same way a sticky note marks the last-read page in a book, certain molecules tag the active genes in a cell so that, after it divides, the same genes are reactivated right away in the new cells.
"What we didn't know, however, was how bookmarking ...
UK government claims that patient choice improves health care is based on flawed research, experts say
2011-10-10
Research which claims to show that the introduction of patient choice in the NHS reduced deaths from heart attacks is flawed and misleading, according to a report* published in The Lancet today (Monday).
The original study was used by the Government to advance its controversial Health and Social Care Bill 2011 and was the basis for the Prime Minister's statement that 'competition is one way we can make things work better for patients'.
In today's report, academics - led by Professor Allyson Pollock of Queen Mary, University of London - point out a series of errors in ...
Lawrenceville Clinic Rodriguez MD Launches a Center for Medical Weight Loss
2011-10-10
Rodriguez MD, a Lawrenceville clinic and bilingual Lawrenceville family practice in Gwinnett County, GA, opened an onsite Center for Medical Weight Loss on Monday October 3, 2011. Striving to help patients safely and effectively lose weight, Rodriguez MD now offers comprehensive, personalized weight loss programs. This includes:
- Body composition analysis
- Doctor-supervised food plans
- Metabolism regulation
- Appetite management
- Lifestyle and motivational coaching
- Science-based activity recommendations
Medical weight loss is physician-directed weight ...
Brain imaging reveals why we remain optimistic in the face of reality
2011-10-10
For some people, the glass is always half full. Even when a football fan's team has lost ten matches in a row, he might still be convinced his team can reverse its run of bad luck. So why, in the face of clear evidence to suggest to the contrary, do some people remain so optimistic about the future?
In a study published today in Nature Neuroscience, researchers at the Wellcome Trust Centre for Neuroimaging at UCL (University College London) show that people who are very optimistic about the outcome of events tend to learn only from information that reinforces their rose-tinted ...
New membrane lipid measuring technique may help fight disease
2011-10-10
Could controlling cell-membrane fat play a key role in turning off disease?
Researchers at the University of Illinois at Chicago think so, and a biosensor they've created that measures membrane lipid levels may open up new pathways to disease treatment.
Wonhwa Cho, distinguished professor of chemistry, and his coworkers engineered a way to modify proteins to fluoresce and act as sensors for lipid levels.
Their findings are reported in Nature Chemistry, online on Oct. 9.
"Lipid molecules on cell membranes can act as switches that turn on or off protein-protein interactions ...
Behind on Paying Your Tax Debt? Let Blue Tax Get Behind You to Find a Resolution
2011-10-10
Often, in this economy, it is easy to get behind. You know you owe taxes to the IRS, but every day bills and financial obligations begin to take priority in order to maintain a reasonable standard of living.
This is the situation Michael (Tecumseh, Kansas) found himself in when he called the offices of Blue Tax in desperation looking for some guidance on how to get the IRS to cease sending him threatening letters about levies and garnishments, knowing that he owed back taxes.
Michael's goal in retaining Blue Tax's services was to protect him from possible collection ...
Novel technique uses RNA interference to block inflammation
2011-10-10
Massachusetts General Hospital (MGH) researchers – along with collaborators from Massachusetts Institute of Technology (MIT) and Alnylam Pharmaceuticals – have found a way to block, in an animal model, the damaging inflammation that contributes to many disease conditions. In their report receiving early online publication in Nature Biotechnology, the investigators describe using small interfering RNA technology to silence the biochemical signals that attract a particular group of inflammatory cells to areas of tissue damage.
"The white blood cells known as monocytes ...
Smarter toxins help crops fight resistant pests
2011-10-10
One of the most successful strategies in pest control is to endow crop plants with genes from the bacterium Bacillus thuringiensis, or Bt for short, which code for proteins that kill pests attempting to eat them.
But insect pests are evolving resistance to Bt toxins, which threatens the continued success of this approach. In the current issue of Nature Biotechnology, a research team led by UA Professor Bruce Tabashnik reports the discovery that a small modification of the toxins' structure overcomes the defenses of some major pests that are resistant to the natural, ...