PRESS-NEWS.org - Press Release Distribution
PRESS RELEASES DISTRIBUTION

Electrons corralled using new quantum tool

'Whispering gallery' effect confines electrons, could provide basis for new electron-optics devices

2015-05-07
(Press-News.org) CAMBRIDGE, Mass--Researchers have succeeded in creating a new "whispering gallery" effect for electrons in a sheet of graphene -- making it possible to precisely control a region that reflects electrons within the material. They say the accomplishment could provide a basic building block for new kinds of electronic lenses, as well as quantum-based devices that combine electronics and optics.

The new system uses a needle-like probe that forms the basis of present-day scanning tunneling microscopes (STM), enabling control of both the location and the size of the reflecting region within graphene -- a two-dimensional form of carbon that is just one atom thick.

The new finding is described in a paper appearing in the journal Science, co-authored by MIT professor of physics Leonid Levitov and researchers at the National Institute of Standards and Technology (NIST), the University of Maryland, Imperial College London, and the National Institute for Materials Science (NIMS) in Tsukuba, Japan.

When the sharp tip of the STM is poised over a sheet of graphene, it produces a circular barrier on the sheet that "acts as a perfect curved mirror" for electrons, Levitov says, reflecting them back toward the center of the circle. This controllable reflectivity is similar, he adds, to so-called "whispering gallery" confinement modes that have been used in optical and acoustic systems -- but these have not been tunable or adjustable.

"In optics, whispering gallery modes are known and useful," Levitov says. "They provide high-quality resonances. But the usual problem in optics is they're not tunable." Similarly, previous attempts to create quantum "corrals" for electrons have used atoms precisely positioned on a surface, which cannot be reconfigured easily.

The confinement in this case is produced by the boundary between two different regions on the graphene surface, corresponding to the "p" and "n" regions in a transistor. In this case, a circular region just beneath the STM tip takes on one polarity, and the surrounding region the opposite polarity, creating a controllable circular junction between the two regions. Electrons inside sheets of graphene behave like particles of light; in this case, the circular junction acts as a curved mirror that can focus and control the electrons.

It's too early to predict what specific uses might be found for this phenomenon, Levitov says, but adds, "Any resonator can be used for a variety of things."

This electron resonator combines several good features. There's clearly something special about having tunability and also high quality at the same time."

Because the new system is based on well-established STM technology, it could be developed relatively quickly into usable devices, Levitov suggests. And conveniently, the STM not only creates the whispering gallery effect, but also provides a means of observing the results, to study the phenomenon. "The tip does double-duty in this case," he says.

This could be a step toward the creation of electronic lenses, Levitov says -- "a concept that intrigues graphene researchers." In principle, these could provide a way of observing objects one-thousandth the size of those visible using light waves.

Electronic lenses would represent a fundamentally different approach from existing electron microscopes, which bombard a surface with high-energy beams of electrons, obliterating any subtle effects within the objects being observed. Electron lenses, by contrast, would be able to observe the ambient low-energy electrons within the object itself.

This could make it possible to study "subtle things about how charge carriers behave at a microscopic level, that you can't see from the outside," Levitov says.

The new work by Levitov and his colleagues provides one piece of such a system -- and potentially of other advanced electro-optical systems, he says, such as negative-refraction materials that have been proposed as a kind of "invisibility cloak." The new whispering-gallery mode for electrons is part of a toolbox that could lead to a whole family of new quantum-based electron-optics devices. It could also be used to create highly sensitive sensors, since such resonators "can be used to enhance your sensitivity to very small signals," Levitov says.

INFORMATION:

The research team also included graduate student Joaquin Rodriguez-Nieva from MIT; Yue Zhao, Jonathan Wyrick, Fabian Natterer, Nikolai Zhitenev, and Joseph Stroscio from NIST; Cyprian Lewandowski from Imperial College London; and Kenji Watanabe and Takashi Taniguchi from NIMS.



ELSE PRESS RELEASES FROM THIS DATE:

Fragments of tRNA suggest a novel mechanism for cancer progression

2015-05-07
For years, scientists have been puzzled by the presence of short stretches of genetic material floating inside a variety of cells, ranging from bacteria to mammals, including humans. These fragments are pieces of the genetic instructions cells use to make proteins, but are too short a length to serve their usual purpose. Reporting in this week's Cell, researchers at Rockefeller have discovered a major clue to the role these fragments play in the body -- and in the process, may have opened up a new frontier in the fight against breast cancer. Specifically, Sohail Tavazoie ...

Rockefeller scientists resolve debate over how many bacteria fight off invaders

2015-05-07
Every inch of our body, inside and out, is oozing with bacteria. In fact, the human body carries 10 times the number of bacterial cells as human cells. Many are our friends, helping us digest food and fight off infections, for instance. But much about these abundant organisms, upon which our life depends, remains mysterious. In research reported May 7 in Cell, scientists at Rockefeller finally crack the code of a fundamental process bacteria use to defend themselves against invaders. For years, researchers have puzzled over conflicting results about the workings of a ...

'Fracture' prints, not fingerprints, help solve child abuse cases

Fracture prints, not fingerprints, help solve child abuse cases
2015-05-07
EAST LANSING, Mich. - Much like a finger leaves its own unique print to help identify a person, researchers are now discovering that skull fractures leave certain signatures that can help investigators better determine what caused the injury. Implications from the Michigan State University research could help with the determination of truth in child abuse cases, potentially resulting in very different outcomes. Until now, multiple skull fractures meant several points of impact to the head and often were thought to suggest child abuse. Roger Haut, a University Distinguished ...

WSU ecologist warns of bamboo fueling spread of hantavirus

2015-05-07
PULLMAN, Wash.--Washington State University researchers say the popularity of bamboo landscaping could increase the spread of hantavirus, with the plant's prolific seed production creating a population boom among seed-eating deer mice that carry the disease. Richard Mack, an ecologist in WSU's School of Biological Sciences, details how an outbreak could happen in a recent issue of the online journal PLOS One. Bamboo plants are growing in popularity, judging by the increased number of species listed by the American Bamboo Society. Some grow in relatively self-contained ...

How to build a new global health framework

2015-05-07
WASHINGTON -- Can a true, robust global health framework be created to help prevent tragedies like Ebola while at the same time allow countries to meet everyday health needs? Georgetown University global health and law experts say it can be done, and in a special issue of "The Lancet" focusing on global health security, they propose specific priorities to transform a fragmented health system into a "purposeful, organized" framework with national health systems at its foundation and an empowered World Health Organization at its apex. "The Ebola epidemic in west Africa ...

The Lancet: Can the Ebola outbreak rejuvenate global health security?

2015-05-07
The west African Ebola epidemic has rekindled interest in global health security, but it has also highlighted a troubling lack of political commitment to public health, and it is far from clear whether the crisis will be enough to rejuvenate global health security, say leading global health experts writing in The Lancet. Through a series of essays [1], the review, which is published as part of a special issue on global health security, explores different perspectives on the wider lessons that can be drawn from the outbreak, including how it has demonstrated the importance ...

How your brain reacts to emotional information is influenced by your genes

2015-05-07
Your genes may influence how sensitive you are to emotional information, according to new research by a UBC neuroscientist. The study, recently published in The Journal of Neuroscience, found that carriers of a certain genetic variation perceived positive and negative images more vividly, and had heightened activity in certain brain regions. "People really do see the world differently," says lead author Rebecca Todd, a professor in UBC's Department of Psychology. "For people with this gene variation, the emotionally relevant things in the world stand out much more." The ...

Plugging up leaky graphene

2015-05-07
For faster, longer-lasting water filters, some scientists are looking to graphene --thin, strong sheets of carbon -- to serve as ultrathin membranes, filtering out contaminants to quickly purify high volumes of water. Graphene's unique properties make it a potentially ideal membrane for water filtration or desalination. But there's been one main drawback to its wider use: Making membranes in one-atom-thick layers of graphene is a meticulous process that can tear the thin material -- creating defects through which contaminants can leak. Now engineers at MIT, Oak Ridge ...

Biting back: Scientists aim to forecast West Nile outbreaks

Biting back: Scientists aim to forecast West Nile outbreaks
2015-05-07
BOULDER--New research has identified correlations between weather conditions and the occurrence of West Nile virus disease in the United States, raising the possibility of being able to better predict outbreaks. The study, by researchers with the National Center for Atmospheric Research (NCAR) and the Centers for Disease Control and Prevention (CDC), finds strong correlations across much of the country between an increased occurrence of West Nile virus disease and above average temperatures in the preceding year. The scientists also find that precipitation influences ...

If you want change, tell a relevant story -- not just facts

2015-05-07
Latin American women in Los Angeles County are twice as likely as white women to contract cervical cancer, according to the Los Angeles County Department of Public Health, and are significantly less likely to be educated about the causes of the disease or to be screened for it. That needs to change, say USC researchers, who are finding ways to make it happen. "Latinas are the ones most at risk and yet health communication campaigns still essentially target white women," said Sheila Murphy, professor at the USC Annenberg School for Communication and Journalism. Murphy ...

LAST 30 PRESS RELEASES:

Are lifetimes of big appliances really shrinking?

Pink skies

Monkeys are world’s best yodellers - new research

Key differences between visual- and memory-led Alzheimer’s discovered

% weight loss targets in obesity management – is this the wrong objective?

An app can change how you see yourself at work

NYC speed cameras take six months to change driver behavior, effects vary by neighborhood, new study reveals

New research shows that propaganda is on the rise in China

Even the richest Americans face shorter lifespans than their European counterparts, study finds

Novel genes linked to rare childhood diarrhea

New computer model reveals how Bronze Age Scandinavians could have crossed the sea

Novel point-of-care technology delivers accurate HIV results in minutes

Researchers reveal key brain differences to explain why Ritalin helps improve focus in some more than others

Study finds nearly five-fold increase in hospitalizations for common cause of stroke

Study reveals how alcohol abuse damages cognition

Medicinal cannabis is linked to long-term benefits in health-related quality of life

Microplastics detected in cat placentas and fetuses during early pregnancy

Ancient amphibians as big as alligators died in mass mortality event in Triassic Wyoming

Scientists uncover the first clear evidence of air sacs in the fossilized bones of alvarezsaurian dinosaurs: the "hollow bones" which help modern day birds to fly

Alcohol makes male flies sexy

TB patients globally often incur "catastrophic costs" of up to $11,329 USD, despite many countries offering free treatment, with predominant drivers of cost being hospitalization and loss of income

Study links teen girls’ screen time to sleep disruptions and depression

Scientists unveil starfish-inspired wearable tech for heart monitoring

Footprints reveal prehistoric Scottish lagoons were stomping grounds for giant Jurassic dinosaurs

AI effectively predicts dementia risk in American Indian/Alaska Native elders

First guideline on newborn screening for cystic fibrosis calls for changes in practice to improve outcomes

Existing international law can help secure peace and security in outer space, study shows

Pinning down the process of West Nile virus transmission

UTA-backed research tackles health challenges across ages

In pancreatic cancer, a race against time

[Press-News.org] Electrons corralled using new quantum tool
'Whispering gallery' effect confines electrons, could provide basis for new electron-optics devices