Graphene is a tunable plasmonic medium

ScienceDaily (June 20, 2012) ? With a beam of infrared light, scientists have sent ripples of electrons along the surface of graphene and demonstrated that they can control the length and height of these oscillations, called plasmons, using a simple electrical circuit.

This is the first time anyone has observed plasmons on graphene, sheets of carbon just one atom thick with a host of intriguing physical properties, and an important step toward using plasmons to process and transmit information in spaces too tight to use light.

"Everybody suspected that plasmons should be there, but seeing is believing. We've imaged them and shown that they propagate. And we've demonstrated that we can control them," said Dimitri Basov, professor of physics at the University of California, San Diego, and senior author of the report published online June 21 in advance of print publication in Nature.

To make the devices, they peeled graphene from graphite, the stuff of pencil lead, and rubbed it onto silicon dioxide chips.

They launched plasmons by shining an infrared laser on the surface of the graphene and measured the waves using the ultrasensitive arm of an atomic force microscope.

The outgoing waves are impossible to measure. But as they reach the edge of the graphene, they reflect like water waves from the wake of a boat bouncing off a pier.

Oscillations returning from the edge add to, or cancel out, subsequent waves, creating a characteristic interference pattern that reveals their wavelength and amplitude.

The scientists showed that pattern could be altered by controlling an electrical circuit formed with electrodes attached to the graphene surface and a layer of pure silicon beneath the chips.

"Here it is," Basov said. "You just take a battery from a flashlight and crank the voltage and you have a tunable plasmonic device."

Just like light can carry complex signals through fiber optics, plasmons could be used to transmit information. But plasmons could carry information within far tighter spaces.

"It's impossible to confine light at nanometer scales because light wavelengths are many hundreds of nanometers," said Zhe Fei, a graduate student in Basov's lab and the first author of the paper. "We used light to excite surface plasmons with a length scale of 100 nanometers or less that can travel at very high speed from one side of the chip to the other."

The performance they observed is promising. These are some of the shortest plasmon wavelengths measured in any material, yet the waves propagate as far as they do in metals like gold. And unlike plasmons on metals, graphene plasmons can be tuned.

A team of scientists working independently in Spain lead by Frank Koppens, Rainer Hillenbrand and Javier Garcia de Abajo has made a similar discovery using graphene film deposited by a gas rather than peeled from graphite. Their report, published in the same issue of Nature, bolsters this evidence for graphene plasmons.

"Graphene optoelectronics and information processing are very promising. We like to see our work contribute to future technology," Basov said. "There also is entirely new, fundamental science coming out of this. By monitoring plasmons, we learn what electrons do in this new form of carbon, how fundamental interactions govern their properties. This is a path of inquiry."

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Story Source:

The above story is reprinted from materials provided by University of California - San Diego, via EurekAlert!, a service of AAAS.

Note: Materials may be edited for content and length. For further information, please contact the source cited above.

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Journal Reference:

1. Z. Fei, A. S. Rodin, G. O. Andreev, W. Bao, A. S. McLeod, M. Wagner, L. M. Zhang, Z. Zhao, M. Thiemens, G. Dominguez, M. M. Fogler, A. H. Castro Neto, C. N. Lau, F. Keilmann, D. N. Basov. Gate-tuning of graphene plasmons revealed by infrared nano-imaging. Nature, 2012; DOI: 10.1038/nature11253

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

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Russia jails two men for giving China nuke secrets

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They Draw and Cook | Veggie Buntch: Vegetarian and vegan ...

While looking for some creative cooking inspiration, I happily came across a lovely, playful site called They Draw & Cook?which feature a collection of recipes submitted by people from around the world. Packed full of amazing, inspired drawings, each expressed very differently depending on the artist, you could spend hours browsing through these food-inspired creations. Here are two to get you started.

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Shenzhou 9 Sparks Renewed Debate On Space Race With China

China had wanted to cooperate with the world in the space venture

China had wanted to join the ISS

The United States of America objected, and barred the Chinese from ever stepping into the ISS

That left China with no other alternative but to construct their own space station

In other words, the space "RACE" has become a race because that's what USA had always wanted

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Jamie Dupree's Washington Insider: GOP highlights empty D.C. buildings

For a third time this year, Republicans in the House will hold a hearing at an unused federal building in Washington, D.C., making the case that Uncle Sam is needlessly spending millions of dollars every year to deal with real estate that could be used for other purposes.

"We've got buildings that have been empty for decades," said Rep. John Mica (R-FL), head of the House Transportation Committee, which oversees federal buildings and the General Services Administration.

Today, Mica and Rep. Jeff Denham (R-CA) will venture just over a mile down Pennsylvania Avenue from the White House to the high-priced area of D.C. known as Georgetown, where an old heating plant sits idle - not far from a bustling tourist area.

"The Georgetown Heating Plant is an example of an underperforming building that if sold or redeveloped to better use could provide a positive return to the taxpayer," Republicans argued in a briefing memo for Tuesday's hearing.

"The facility was only declared surplus property in November 2011, 11 years after it was closed as a steam plant," read the memo, which says the GSA is aiming to sell the building by this fall.

"This city is full of vacant buildings," said Mica, who has railed against the cost of keeping federal buildings in the GSA inventory when no federal agencies are using them.

Republicans have been pressing the GSA for a full list of surplus federal property, with some lawmakers wanting to sell what is "excess" and others wanting to find ways to leverage new development around federal parcels.

But Republicans have been living in a "Catch-22" with the GSA - which hasn't exactly moved quickly to turnover data on surplus property - as Congress can't try to sell surplus property if the federal agency in charge of that property won't tell them what property is considered surplus.

The bottom line here is that this is about money; Republicans estimate that the feds spent $1.7 billion in 2009 for operating costs at "under-utilized" buildings, as well as $134 million for "excess buildings."

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Women's rights law no match for Kurdistan tradition

In June 2011, Iraqi Kurdistan passed a landmark law that criminalised female circumcision and domestic violence, but one year on, activists remain frustrated with its patchwork implementation.

In what is a conservative society even by Middle East standards, the passage of the law last year was hailed by rights groups and NGOs as a major step forward after years of struggle.

The law punishes physical, sexual and psychological assault committed within the family, creates conditions for the protection of victims and mandates the establishment of specialised courts.

It also carries penal and financial punishments for those who promote or practice female genital mutilation.

Kurdistan is a three-province region in Iraq's north that enjoys great autonomy from the central government, with its own parliament, budget, and armed forces.

The region benefits from a markedly more stable security situation than the rest of the country, and an improving economy, two factors that mean life for women in Kurdistan is widely regarded as better than Iraq's other provinces.

But terrible problems remain, one of which is female genital mutilation.

Though often perceived as a problem mostly prevalent in Africa, the practice is widespread in Kurdistan, according to German NGO Wadi, which published a report in 2010 on the subject, based on interviews with 1,700 women in the region.

According to that report, 72.7 percent of women in the region's two biggest provinces of Arbil and Sulaimaniyah were victims of female genital mutilation, with the rate rising to almost 100 percent in some areas.

Wadi pointed to a "clear link" between the practice and illiteracy, pegged at 51.1 percent among women in Kurdistan.

The adoption of the law marked a "big victory", said Suzan Aref, head of the Women's Empowerment Organisation, a local NGO established in June 2004.

"At least now we are talking about this," she said.

Pakhshan Zangana, secretary general of the High Council for Women's Affairs, a Kurdish government agency, agrees: "In our society, just to recognise domestic violence is very important."

"Society recognised that, yes, we do have domestic violence, it is a crime. This is so important.

"In other societies, it is (considered) the right of the family, that they have the right to do anything," she said.

But both women agree the battle will not be won until the law is fully applied, which appears a long way off.

"Yes, we have laws, but... we don't have implementation," Aref said. "This is a big problem."

"You cannot find that the numbers (for female genital mutilation) have reduced because of this law, because no one knows about it," she said, adding: "We need a campaign of awareness."

Police in the region are widely seen as reluctant to investigate deeper in to violence against and the causes of apparent suicides, which may well be so-called honour killings, Aref noted.

Women see the law not being applied, she said, and "they lose hope."

Ramziya Zana, head of the Arbil-based Gender Studies and Information Centre Organisation, is more direct.

"It has been one year since the law was passed, and it has still not been applied," she said. "It's a disaster. Now, you have to either return the law to parliament, or apply it".

According to her, judges and religious leaders have stood in the way of the law's full implementation.

"Most judges think this is harmful for the family," and those who apply it "can be counted on one hand," she said. As for religious leaders in Kurdistan, "there is nothing in the law that they like" and many have called for it to be amended or scrapped.

Zangana admitted there have been difficulties in applying the new law, particularly in the creation of special courts, but insisted an implementation plan was being developed with the United Nations, and said patience was needed.

"It is new in a society like our's -- anything against traditional culture, we cannot measure within months," she said.

Aref also said she remained optimistic about long-term trends in the region, but voiced regrets that the law did not appear to address the root causes of domestic violence.

"We are dealing with the results of the problem, not the roots," she said. "There is something that leads to honour killings and suicide -- forced or early marriage, illiterate women who have no income."

"You can see how the mentality (of people in Kurdistan) cannot accept women's issues," she said.

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