Spin Battery: Physicist Develops Battery Using New Source Of Energy

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ScienceDaily (Mar. 12, 2009) — Researchers at the University of Miami and at the Universities of Tokyo and Tohoku, Japan, have been able to prove the existence of a "spin battery," a battery that is "charged" by applying a large magnetic field to nano-magnets in a device called a magnetic tunnel junction (MTJ).

The new technology is a step towards the creation of computer hard drives with no moving parts, which would be much faster, less expensive and use less energy than current ones. In the future, the new battery could be developed to power cars.
The study is published in the journal Nature and is available online.
The device created by University of Miami Physicist Stewart E. Barnes, of the College of Arts and Sciences and his collaborators can store energy in magnets rather than through chemical reactions. Like a winding up toy car, the spin battery is "wound up" by applying a large magnetic field --no chemistry involved. The device is potentially better than anything found so far, said Barnes.
"We had anticipated the effect, but the device produced a voltage over a hundred times too big and for tens of minutes, rather than for milliseconds as we had expected," Barnes said. "That this was counterintuitive is what lead to our theoretical understanding of what was really going on."
The secret behind this technology is the use of nano-magnets to induce an electromotive force. It uses the same principles as those in a conventional battery, except in a more direct fashion. The energy stored in a battery, be it in an iPod or an electric car, is in the form of chemical energy. When something is turned "on" there is a chemical reaction which occurs and produces an electric current. The new technology converts the magnetic energy directly into electrical energy, without a chemical reaction. The electrical current made in this process is called a spin polarized current and finds use in a new technology called "spintronics."
The new discovery advances our understanding of the way magnets work and its immediate application is to use the MTJs as electronic elements which work in different ways to conventional transistors. Although the actual device has a diameter about that of a human hair and cannot even light up an LED (light-emitting diode--a light source used as electronic component), the energy that might be stored in this way could potentially run a car for miles. The possibilities are endless, Barnes said.
"There are magnets hidden away in many things, for example there are several in a mobile telephone, many in a car, and they are what keeps your refrigerator closed," he said. "There are so many that even a small change in the way we understand of how they work, and which might lead to only a very small improvement in future machines, has a significant financial and energetic impact."
Adapted from materials provided by University of Miami, via EurekAlert!, a service of AAAS.

Slow Light - By Lene Hau et al.

A pulse of light injected into a Bose-Einstein Condensate (BEC) can be slowed to a tiny fraction of the speed of light in a vacuum. In the movie, the top animation shows how the information in a pulse is compressed when it enters a BEC (contained inside the blue arc), and then returned to it's original form as it exits. In the movie, the lower animation illustrates a race between a light pulse that passes through a cigar-shaped BEC blob and a light pulse traveling in free space, demonstrating how light can be controlled with BECs. Techniques that slow light could potentially lead to devices that manipulate light in the same way that microelectronic chips and computers manipulate electrical signals and data.Light comes in units of energy called photons which have no mass, only energy and momentum. Modern physics tells us that massless particles must move at the speed c in a vacuum. It's possible to slow light down by making it interact with matter and, in a sense, converting photons to something with mass. That's one way to understand what Lene Hau and colleagues at the Rowland Institute of Science did in 1999 when they slowed light to 17 miles per hour in a Bose Einstein Condensate (BEC) made of ultracold sodium atoms. The BEC is usually opaque, but the researchers made the material transparent by exposing it to a specific arrangement of laser beams. The lasers allowed incoming photons to combine with atoms to form a hybrid particle known as a polariton. Because polaritons get mass from the atoms, they move slower than c. In a BEC, many atoms condense to form one large, super atom. The super atoms are very heavy, and so are the polaritons formed with the incoming photons, and as a result they move much slower than c.In 2001, Ron Walsworth, Mikhail Lukin and colleagues at the Harvard-Smithsonian Center for Astrophysics formed slow moving polaritons in a vapor of rubidium atoms, in much the same way that Hau slowed light in a BEC. By turning down the lasers that made the vapor transparent, the researchers gradually reduced the portion of the polaritons that were made of photons and increased the portion made of atoms, and the light was effectively stopped and stored in the vapor. By turning the lasers back up, the researchers converted the polaritons back into photons, which then resumed their speed-of-light travel. At about the same time that this work was being done, Hau's group stopped light in a BEC.Among other things, stopping light might provide a way to store data in future optical computers, or lead to new ways to manipulate light.

Do you have an eye for entanglement?

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Taking a good look at cloning

Experiments that reveal the weirdness of the quantum world usually involve precise and highly specialized equipment. But now physicists in Switzerland and the UK have proposed a way of using human vision to observe the purely quantum effect of "entanglement".
The experiment — which has yet to be performed in the lab — would involve entangling a pair of photons and then creating thousands of identical copies of one of the pair such that they could be seen by the human eye.
Entangled particles have a much stronger relationship than that allowed by classical mechanics. For example, the polarization of one photon is revealed instantly by measuring the polarization its entangled partner, regardless of the distance between the photons.
The new experiment, which has been proposed by Nicolas Gisin and colleagues at the University of Geneva and University of Bristol, would first involve creating a pair of entangled photons. This could be done, for example, by passing light through a non-linear crystal in which a higher-energy photon is absorbed followed by the emission of two lower-energy photons (arXiv:0902.2896).

Cloning photons:

One of the photons is then “cloned” to create thousands of identical photons. This is done by stimulated emission — the same process behind a laser — whereby the original photon is sent through a pumped optical medium.
Because the clones are created in a coherent quantum process, it produces a pulse of light that is intense enough to be seen with the naked eye — yet is entangled with the second original photon. Measuring the polarization of the pulse will therefore reveal the polarization of the second photon.
The team proposes to measure the polarization of the pulse by passing it through a polarizing filter, which allows light with parallel polarization to pass through while deflecting light with perpendicular polarization by 90°. Two human observers — one looking along the parallel path and the other the perpendicular path — could then determine the polarization of each pulse.

Meanwhile, the polarization of the second photon of the pair would be determined by passing it through a similar polarizing filter that is monitored by two sensitive photon detectors.

Predicting the outcome:

If the experiment is a success, the humans should be able to predict the outcome of the measurement on the second photon based on the observed polarization of the pulse. In other words, if the pulse is vertically polarized, then the second photon will be horizontally polarized.
While entanglement in photons was first observed over 30 years ago, Gisin is keen to point out an important distinction between this and previous experiments. In earlier work, the choice of measurement that forces the entangled pair into distinct polarization states is made before that state is amplified to a level where it can be perceived by a human observer. For example, a single photon is passed through a polarizing filter and then converted into an amplified electrical pulse by a detector.
By contrast, in this experiment the entangled state is amplified to the human level before the measurement is made — effectively bringing the observer one step closer to the weird world of quantum mechanics. Indeed, Gisin believes that, if successful, the experiment could be extended to clone the second entangled photon and use a total of four human observers to verify entanglement.

'Elegant experiment':

Seth Lloyd at the Massachusetts Institute of Technology told physicsworld.com that the proposal “does a considerable service by devising an elegant experiment where the human eye functions in a very efficient way as an entanglement detector”. However, he also points out that the eye is an extremely efficient detector of light, so it is not surprising that is could be used to detect entanglement.
Indeed, the challenges involved in actually doing the experiment are mostly related to the cloning process, according to Gisin. “Cloning cannot be perfect”, he explained, adding that unwanted spontaneous emission during cloning would create a significant number of photons that were not entangled.
This problem could be reduced using a technique called “phase covariant” cloning, but not eliminated. As a result, the experiment would have to be repeated many times over before the observers see enough entangled pulses to verify the effect.
Another challenge, according to Gisin, is producing cloned pulses of green light, which the eye is most sensitive to. Most cloning systems currently produce photons in the infrared.
“First we plan to amplify the photon so it can be seen”, said Gisin. “The rest should be relatively easy.”

About the author:
Hamish Johnston is editor of physicsworld.com

New Genre Of Sugar-coated 'Quantum Dots' For Drug Delivery

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ScienceDaily (Mar. 11, 2009) — Scientists in Switzerland are reporting an advance that could help tap the much-heralded potential of "quantum dots"— nanocrystals that glow when exposed to ultraviolet light — in the treatment of cancer and other diseases.

They are publishing the first study showing that giving quantum dots an icing-like cap of certain sugars makes these nanoparticles accumulate in the liver but not other parts of the body. That selective targeting could be used to deliver anti-cancer drugs to one organ, without causing the body-wide side-effects that occur with existing cancer drugs, they suggest.
Their study is in the Feb. 18 issue of the Journal of the American Chemical Society, a weekly publication.
In the new report, Peter H. Seeberger and colleagues note that quantum dots, about 1/5,000th the width of a human hair, are used in solar cells, medical diagnostic imaging, and electronics. Scientists believe these particles also show promise for drug delivery for treating cancer and other diseases. However, researchers still have not found an ideal way to target these dots to specific tissues or organs in order to maximize their effectiveness and limit toxicity.
They describe development of a new type of quantum dot coated with certain sugar molecules that are attracted to receptors in specific tissues and organs. In a study with laboratory mice, the scientists coated quantum dots with either mannose or galactosamine, two sugars that accumulate selectively in the liver. The sugar-coated dots became three times more concentrated in the mice livers than the regular dots, demonstrating their higher specificity, the researchers say.
Journal reference:
Kikkeri et al. In Vitro Imaging and in Vivo Liver Targeting with Carbohydrate Capped Quantum Dots. Journal of the American Chemical Society, 2009; 131 (6): 2110 DOI: 10.1021/ja807711w
Adapted from materials provided by American Chemical Society, via EurekAlert!, a service of AAAS.

Mechanism To Increase Magnetic Response Of Ferromagnetic Semiconductor Identified

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ScienceDaily (Mar. 11, 2009) — When squeezed, electrons increase their ability to move around. In compounds such as semiconductors and electrical insulators, such squeezing can dramatically change the electrical- and magnetic- properties.

Under ambient pressure, Europium oxide becomes ferromagnetic only below 69 Kelvin, limiting its applications. However, its magnetic ordering temperature is known to increase with pressure, reaching 200 Kelvin when squeezed by 150,000 atmospheres. The relevant changes in electronic structure responsible for such dramatic changes, however, remained elusive.
Now scientists at the U.S. Department of Energy's Argonne National Laboratory have manipulated electron mobility and pinpointed the mechanism controlling the strength of magnetic interactions- and hence the material's magnetic ordering temperature.
"EuO is a ferromagnetic semiconductor and is a material that can carry spin polarized currents, which is an integral element of future devices aimed at manipulating both the spin and the charge of electrons in new generation microelectronics," Argonne's Postdoctoral researcher Narcizo Souza-Neto said.
Using powerful X-rays from the Advanced Photon Source to probe the material's electronic structure under pressure, Souza-Neto and Argonne Physicist Daniel Haskel report in the February 6 issue of Physical Review Letters that localized, 100 percent polarized Eu 4f electrons become mobile under pressure by hybridizing with neighboring, extended electronic states. The increased mobility enhances the indirect magnetic coupling between Eu spins resulting in a three-fold increase in the ordering temperature.
While the need for large applied pressures may seem a burden for applications, large compressive strains can be generated at interfacial regions in EuO films by varying the mismatch in lattice parameter with selected substrates. By pinpointing the mechanism the research provides a road map for manipulating the ordering temperatures in this and related materials, e.g., through strain or chemical substitutions with the ultimate goal of reaching 300 Kelvin (room temperature).
"Manipulation of strain adds a new dimension to the design of novel devices based on injection, transport, and detection of high spin-polarized currents in magnetic/semiconductor hybrid structures", Haskel said.
Other authors in the paper are graduate student Yuan-Chieh Tseng (Northwestern U.) and Gerard Lapertot (CEA-Grenoble).
Funding for this research was provided by the U.S. Department of Energy's Office of Science.
Adapted from materials provided by DOE/Argonne National Laboratory.

Rare Single Top Quark Discovered In Collider Experiments

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ScienceDaily (Mar. 10, 2009) — Scientists of the CDF and DZero collaborations at the Department of Energy’s Fermi National Accelerator Laboratory have observed particle collisions that produce single top quarks. The discovery of the single top confirms important parameters of particle physics, including the total number of quarks, and has significance for the ongoing search for the Higgs particle at Fermilab’s Tevatron, currently the world’s most powerful operating particle accelerator.

Previously, top quarks had only been observed when produced by the strong nuclear force. That interaction leads to the production of pairs of top quarks. The production of single top quarks, which involves the weak nuclear force and is harder to identify experimentally, has now been observed, almost 14 years to the day of the top quark discovery in 1995.
Searching for single-top production makes finding a needle in a haystack look easy. Only one in every 20 billion proton-antiproton collisions produces a single top quark. Even worse, the signal of these rare occurrences is easily mimicked by other “background” processes that occur at much higher rates.
"Observation of the single top quark production is an important milestone for the Tevatron program," said Dr. Dennis Kovar, Associate Director of the Office of Science for High Energy Physics at the U.S. Department of Energy. "Furthermore, the highly sensitive and successful analysis is an important step in the search for the Higgs."
Discovering the single top quark production presents challenges similar to the Higgs boson search in the need to extract an extremely small signal from a very large background. Advanced analysis techniques pioneered for the single top discovery are now in use for the Higgs boson search. In addition, the single top and the Higgs signals have backgrounds in common, and the single top is itself a background for the Higgs particle.
To make the single-top discovery, physicists of the CDF and DZero collaborations spent years combing independently through the results of proton-antiproton collisions recorded by their experiments, respectively. Each team identified several thousand collision events that looked the way experimenters expect single top events to appear. Sophisticated statistical analysis and detailed background modeling showed that a few hundred collision events produced the real thing. On March 4, the two teams submitted their independent results to Physical Review Letters.
The two collaborations earlier had reported preliminary results on the search for the single top. Since then, experimenters have more than doubled the amount of data analyzed and sharpened selection and analysis techniques, making the discovery possible. For each experiment, the probability that background events have faked the signal is now only one in nearly four million, allowing both collaborations to claim a bona fide discovery that paves the way to more discoveries.
“I am thrilled that CDF and DZero achieved this goal,” said Fermilab Director Pier Oddone. “The two collaborations have been searching for this rare process for the last fifteen years, starting before the discovery of the top quark in 1995. Investigating these subatomic processes in more detail may open a window onto physics phenomena beyond the Standard Model.”
The two articles submitted to Physical Review Letters are entitled "Observation of single top quark production" and "First observation of electroweak single top quark production."
Adapted from materials provided by DOE/Fermi National Accelerator Laboratory.

Super Atoms Turn Periodic Table Upside Down

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http://www.sciencedaily.com/releases/2008/07/080701092153.htm

ScienceDaily (July 2, 2008) — Researchers at Delft University of Technology (TU Delft) in The Netherlands have developed a technique for generating atom clusters made from silver and other metals. Surprisingly enough, these so-called super atoms (clusters of 13 silver atoms, for example) behave in the same way as individual atoms and have opened up a whole new branch of chemistry.
If a silver thread is heated to around 900 degrees Celsius, it will generate vapour made up of silver atoms. The floating atoms stick to each other in groups. Small lumps of silver comprising for example 9, 13 and 55 atoms appear to be energetically stable and are therefore present in the silver mist more frequently that one might assume. Prof. Andreas Schmidt-Ott and Dr. Christian Peineke of TU Delft managed to collect these super atoms and make them suitable for more detailed chemical experiments.
Science
The underlying mechanism governing this stability in super atoms was described in Science by scientists from Virginia Commonwealth University in 2005. They had discovered metal super atoms, but from aluminium. Their aluminium clusters of 13, 23 and 37 atoms reacted in the same way as individual atoms because they comprised electrons that revolved around the atom cluster as a whole. These so-called outer layers were strikingly similar to the outer layers of elements from the periodic table.
The super atoms gave the periodic table a third dimension as it were, according to Schmidt-Ott: 'The chemical properties of the super atoms that have been identified up until now are very similar to those of elements in the periodic table, because their outer layers are much the same. However, we may yet discover super atoms with a different outer layer, giving us another set of completely new properties.'
Schmidt-Ott hopes to find atom clusters with new unique magnetic, optical or electrical properties, which would also be stable enough to create crystals or other solid forms. Potential applications include catalysts in fuel and extra-conductive crystals.
Pure
So although super atoms are nothing new, thanks to TU Delft the particles can now be collected in a very pure form and selected according to size, thereby making them suitable for chemical experiments.
A detailed account can be read in the new edition of TU Delft magazine Delft Outlook.

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