Recently in Condensed Matter Physics Category

Science News: Studying with the radio on may not be the best way to remember what you've read. But scientists have now built a data storage device whose memory gets a boost from noise.

The device can store one bit of information, such as a 0 or a 1, only when surrounded by electronic noise, which is normally a problem in computer circuits.

"If you remove the noise, it doesn't store the bit at all," says Diego Grosz of the Instituto Tecnológico de Buenos Aires, a coauthor of the study.

Related Link
One-bit stochastic resonance storage device

Nature: The fractional quantum Hall effect (FQHE) is a fascinating form of collective electronic behavior.

It arises when electrons in a strong magnetic field—applied at a right angle to the plane in which the electrons flow—act together to behave like particles with a charge that is a fraction of an electron's charge.

Its observation requires the use of two-dimensional systems virtually free of disorder. This is why, since its discovery by Daniel Tsui and Horst Störmer in 1982—for which they won the 1998 Nobel Physics prize—the effect has been studied in ultrapure semiconductor heterostructures (devices that contain thin layers of one or more semiconductors) grown in an ultrahigh vacuum.

Two papers, one by Xu Du and colleagues and Kirill I. Bolotin and colleagues, show that the FQHE can also be observed in graphene—a one-atom-thick sheet of graphitic carbon, the production of which requires no more sophistication than a common adhesive tape to manually exfoliate graphite in ambient conditions

Related Links
Fractional quantum Hall effect and insulating phase of Dirac electrons in graphene
Observation of the fractional quantum Hall effect in graphene

Nature: Materials that combine ferroic properties—such as ferromagnetism and ferroelectricity—are highly desirable, but rare. A new class of multiferroic solids heralds a fresh approach for making such materials.

Multiferroics are attractive candidates for use in electrically controllable microwave elements, magnetic-field sensors and possibly even in spintronics.

Related Link
Multiferroic behavior associated with an order−disorder hydrogen bonding transition in metal−organic frameworks (MOFs) with the perovskite ABX₃ architecture

Science: Since the work of James Clerk Maxwell and Heinrich Hertz, we have known that light is an electromagnetic wave. An intricate mechanism generates magnetic fields around the electric fields, and vice versa. In the optical-wavelength range, experimental studies have been limited to probing only the electric-field components.

In Science, Matteo Burresi and colleagues report direct measurements of the magnetic-field components of light obtained with a nanostructured metallic probe at the tip of a sharp glass fiber.

Related Link
Probing the magnetic field of light at optical frequencies

Nature News: Physicists have created a black hole for light that can fit in your coat pocket. Their device, which measures just 22 centimeters across, can suck up microwave light and convert it into heat

Various: A series of papers in Science and Nature report new results on spin ices and monopoles.

The Nature paper

Spin ices are an exotic class of crystalline solids that are rare, three-dimensional systems in which the magnetic moments (spins) of the ions remain disordered even at the lowest temperatures available writes Shivaji Sondhi in Nature. This means that the geometrical layout of the atoms are such that the norths and souths are never able to align in a satisfactory way and so the magnets continually flip up and down trying to find a stable position says Hannah Delvin in the London Times.

The material has a second property, at regular intervals on the lattice the magnetic fields of individual atoms add up to produce essentially isolated north or south charges, behaving as point-like objects that are the condensed-matter versions of Paul Dirac's theoretical magnetic monopoles—particles that, unlike iron magnets, have a single magnetic pole and hence carry an overall magnetic charge.

Initially, it was not evident that their charge could be measured in a straightforward way. Magnetic monopoles live in a lattice at a moderate density under normal laboratory conditions—not the sort of setting in which you could carry out a magnetic version of Millikan and Fletcher's oil-drop experiment to determine the electric charge of the electron.

But Steve Bramwell of the London Centre for Nanotechnology and colleagues in Nature report a measurement of the magnetic charge of the monopoles in spin ice that is in surprisingly good agreement with the theoretical prediction.

"It is not often in the field of physics you get the chance to ask, ‘How do you measure something?’, and then go on to prove a theory unequivocally," said Bramwell to Delvin. "This is a very important step to establish that magnetic charge can flow like electric charge."

The Science papers

In Science, two groups also report measurements from neutron-scattering experiments showing that the low-energy excitations in spin ices are reminiscent of magnetic monopoles writes Michel J. P. Gingras.

These dissociated north and south poles diffuse away from each other in these oxides and leave behind a "Dirac string" of reversed spins that can be seen as patterns in the intensity of scattered neutrons.

Related Links
Discovery of ‘magnetricity’ marks important advance in physics London Times
Measurement of the charge and current of magnetic monopoles in spin ice Nature
Observing Monopoles in a Magnetic Analog of Ice Science
Magnetic Coulomb Phase in the Spin Ice Ho₂Ti₂O₇ Science
Dirac Strings and Magnetic Monopoles in the Spin Ice Dy₂Ti₂ Science

Science: Ferromagnets, such as those made of iron or nickel, are called itinerant because the electrons whose spins aligned to create the magnetic state are extended and are the same as the ones responsible for conduction. Ferromagnetism was a mystery for classical physics, and its explanation in terms of spin, exchange interactions, and repulsions between identical particles was a triumph of early quantum mechanics.

However, it proved difficult to apply these early models to real ferromagnets in a quantitative way, both because the simple models neglect important features relevant in real materials and because theoretical tools to properly treat the strong correlation problem have only recently been developed. Fortunately, the simple models studied in the early days of quantum mechanics can also be applied to fermions other than electrons. In Science a paper discusses new evidence for an analog of ferromagnetism in an ultracold gas of neutral lithium-6 atoms. When repulsive interactions between these freely moving particles are sufficiently strong, a transition to ferromagnetic ordering is seen.

Related Link
Itinerant Ferromagnetism in a fermi gas of ultracold atoms

Science News: By linking the electrical currents of two superconductors large enough to be seen with the naked eye, researchers have extended the domain of observable quantum effects. Billions of flowing electrons in the superconductors can collectively exhibit a weird quantum property called entanglement, usually confined to the realm of tiny particles, say scientists in Nature.

"It's an exciting piece of work," comments physicist Steven Girvin of Yale University. "People are interested in pushing the boundaries of quantum mechanics."

Science: The Moon isn't made of green cheese and almost certainly doesn't harbor hypothetical particles called "strangelets," an analysis of lunar soil has shown. The result undermines a possible strangelet sighting a decade ago and strengthens the case that the bizarre particles, which protesters once feared might emerge from an atom smasher and consume Earth, don't exist.

"I'm not surprised," says Frank Wilczek, a theorist at the Massachusetts Institute of Technology (MIT) in Cambridge. "It would be a great discovery to find strangelets, but the theoretical case for them is pretty shaky." Still, he says, "it's not crazy" to look for them.

Science: As they prepare to restart the Large Hadron Collider, accelerator physicists are confident that, instead of suffering a second catastrophic breakdown, the world's largest atom smasher will perform to the standards set by its predecessors—and give them lots of smaller headaches to struggle with.

Related News Pick
CERN confirms that LHC will run at 3.5 TeV
Students, researchers hit by Large Hadron Collider glitches

Nature: Certain insulators have conducting surfaces that arise from subtle chemical properties of the bulk material. The latest experiments suggest that such surfaces may compete with graphene in electronic applications.

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Topological surface states protected from backscattering by chiral spin texture
A tunable topological insulator in the spin helical Dirac transport regime

Science News: In a new study, researchers found telltale signs of quantum weirdness lurking in an optical trick called ghost imaging. Discovered over a decade ago, ghost imaging allows researchers to create an image of something using light that never bounced off the actual object. The new work adds to the debate over whether ghost imaging is quantum in nature, or if normal, everyday physics can explain the phenomenon.

Related Link
Holographic Ghost Imaging and the Violation of a Bell Inequality. Physical Review Letters, in press

Physics Today: CERN's Director General, Rolf Heuer has confirmed that the Large Hadron Collider will run at 3.5 TeV leading to collisions at 7 TeV when it is turned on in November.

"We've selected 3.5 TeV to start," said Heuer, "because it allows the LHC operators to gain experience of running the machine safely while opening up a new discovery region for the experiments."

The lower energies are because not all the magnets appear to be working at full strength, and the copper stabilizer connections cannot be run at the higher energies.

Last year the LHC suffered a critical failure when one of the 10,000 high-current superconducting electrical connections failed. CERN has been cooling down and testing various sectors of the collider in order to track down the bad connectors.

The tests on the final two sectors concluded last week and have revealed no more major problems. This means that no more repairs are necessary for safe running this year and next.

"The LHC is a much better understood machine than it was a year ago," said Heuer. "We can look forward with confidence and excitement to a good run through the winter and into next year."

The procedure for the 2009 start-up will be to inject and capture beams in each direction, take collision data for a few shifts at the injection energy, and then commission the ramp to higher energy.

The first high-energy data should be collected in December after the first beam of 2009 is injected. The LHC will run at 3.5 TeV per beam until a significant data sample has been collected and the operations team has gained experience in running the machine.

Gradually the machine will be raised up towards 5 TeV per beam. At the end of 2010, the LHC will be run with lead ions for the first time. After that, the LHC will shut down and work will begin on moving the machine towards 7 TeV per beam.

Science News: A macromolecule that was accidentally discovered when scientists left stuff sitting on a lab bench seems to soak up atmospheric carbon dioxide.

The original find was made by a research team led by chemists at the University of Southampton in England. They were trying to design and create molecules that could capture negatively charged ions, such as chlorides and phosphates, on the surfaces of bioengineered cells.

In one experiment, the researchers set aside an alkaline solution of various organic substances to evaporate, says geochemist John A. Tossell, author of the new study. When analyzing the crystals that formed, the team found that the organic macromolecule that made up the crystal unexpectedly contained carbonates, which form in solutions containing carbon dioxide.

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Catching CO2 in a Bowl

Nature: A crystal can grow only if all of its atomic or molecular building blocks fit into the periodic lattice. This is true even for colloidal crystals, which form through the ordered self-assembly of micrometer-sized particles. The requirement for periodicity puts stringent constraints on the variation in the size of particles that can be incorporated into a given colloidal crystalline lattice.

But reporting in Angewandte Chemie, Ashlee St. John Iyer and L. Andrew Lyon show that crystals made of microgel particles are much more tolerant of particle size variations than was expected. This surprising feature might have practical implications for the design of ordered colloidal materials.

Related Link
Lyon Research Group
Payne Laboratory

Nature News: Until recently, string theory—long heralded as a 'theory of everything'—hadn't been particularly good at explaining anything.

But at a workshop this month at the Kavli Institute for Theoretical Physics in Santa Barbara, California, scientists have been using the theory to make progress in tackling one of the biggest puzzles in condensed-matter physics: the origin of high-temperature superconductivity.

Nature: Physicists often state that nuclear shell structure—the way in which protons and neutrons are arranged within a nucleus—is the cornerstone of any satisfactory description of an atomic nucleus. But over the past decade it has become apparent that the exact number of particles required to fill a particular shell is not as fixed as was once thought. The results of two experiments, one by Kanungo et al. reported in Physical Review Letters, and the other by Hoffman et al. in Physics Letters B, add significantly to the discussion. They demonstrate that ²⁴O, the oxygen isotope with proton number Z = 8 and neutron number N = 16, is a doubly magic nucleus. This result is all the more surprising because ²⁴O is also the heaviest oxygen isotope to exist.

Related Links
One-neutron removal measurement reveals ²⁴O as a new doubly magic nucleus
Evidence for a doubly magic ²⁴O

The Economist: A few years ago Yadong Yin was experimenting with tiny beads that changed color when a magnetic field was applied to them. This was interesting but there was no obvious way to turn them into a product

Now Yin and his colleagues at the University of California, Riverside, have come up with possible applications that range from a new type of paint to lipsticks and giant advertising billboards.

Yin’s beads are magnetochromatic microspheres. They are made from tiny blobs of polymer that contain particles of iron oxide. The structure of these particles changes in a magnetic field in a way that produces “interference” colors when light is shone on them.

It is the rearrangement of the particles’ microstructures that produces the pertinent detail.

The new research appears in the 15 June Journal of the American Chemical Society.

Nature: LaHaye and colleagues have taken an important step towards the observation of quantum phenomena in nearly macroscopic moving objects.

They report experimental evidence of an intriguing interplay between a superconducting artificial atom and a micrometre-size mechanical resonator. Remarkably, their findings can be described using the 'language' of radiation–matter interactions, which has also been successful in explaining the coupling of a superconducting artificial atom to microwave photon.

Related Link
Nanomechanical measurements of a superconducting qubit

CNET News: IBM already had technology that could measure extremely subtle forces among atoms, but a nanotechnology development at the company's Zurich Research Laboratory shows a new level of sensitivity: the ability to distinguish positively charged atoms from those that are neutral or negatively charged.

The atomic force microscope maps what's below by detecting subtle changes in forces of attraction.

Researchers at the Zurich lab, along with colleagues at the University of Regensburg and Utrecht University, used an atomic force microscope (AFM) with a tuning-fork detector arrangement on the tip of its probe to distinguish among gold atoms that were positively charged, neutral, or negatively charged. The researchers describe their approach in the June 12 issue of Science.

Related Press Release
IBM scientists directly measure charge states of atoms using an atomic force microscope

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Novel Probes for Molecular Electronics

Science: The ability to observe individual chemical reactions in real time is reshaping our understanding of molecular processes, revealing subtleties previously hidden in ensemble averages. For example, single-molecule fluorescence detection methods have revolutionized optical microscopy and in situ studies of chemical and biological systems. Liquid cell in situ transmission electron microscopy (TEM) is poised to write a new chapter in the solution synthesis and processing of materials. Haimei Zheng and colleagues use a TEM liquid cell that allows liquids to be examined within the vacuum environment of a TEM in an elegant experiment that uncovers dynamic processes in the growth of platinum (Pt) nanocrystals.

Related Link
Observation of Single Colloidal Platinum Nanocrystal Growth Trajectories

AFP: A team of French physicists led by Jean-Yves Bigot of the Institute of Materials Physics and Chemistry in Strasbourg say they have used a "femtosecond" laser, using ultra-fast bursts of laser light, to alter electron spin and thus speed up retrieval and storage.

The technique could increase the speed at which data is written and read from a hard drive up to 100,000 times, they say in this week's Nature Physics.

The work builds upon Albert Fert and Peter Gruenberg's discovery that tiny changes in magnetic fields can yield a large electric output. Their research led to the creation of a new electronics field called "spintronics" that relies on electron spin to store data; however, sensors for reading that data until now were too slow to be effective.

"Our method is called the photonics of spin, because it is photons [particles of light] that modify the state of the electrons' magnetisation" on the storage surface, Bigot told AFP.

Related Physics Today articles

Discoverers of Giant Magnetoresistance Win this Year's Physics Nobel (December 2007)
Quantum Spin Hall Effect Shows up in a Quantum Well Insulator, Just as Predicted (January 2008)
Magnetic Semiconductors Enable Efficient Electrical Spin Injection (April 2000)

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Coherent ultrafast magnetism induced by femtosecond laser pulses

Science: Graphene holds enormous promise for transistors and other electronic devices. But it is already making an impact in the arcane world of high-energy physics.

That's because electrons in graphene don't behave like electrons in a standard metal. In the lattice of a typical metal, electrons feel the push and pull of surrounding charges as they move. As a result, moving electrons behave as if they have a different mass from their less mobile partners. When electrons move through graphene, however, they act as if their mass is zero--behavior that makes them look more like neutrinos streaking through space near the speed of light.

At such "relativistic" speeds, particles don't follow the usual rules of quantum mechanics. Instead, physicists must invoke the mathematical language of quantum electrodynamics, which combines quantum mechanics with Albert Einstein's relativity theory. Even though electrons course through graphene at only 1/300 the speed of neutrinos, physicists realized several years ago that the novel material might provide a test bed for studying relativistic physics in the lab.

Science: Superfluid helium is best known for its ability to flow without resistance. Superfluids also differ from ordinary fluids in that they fail to respond to a slow steady rotation says John Saunders in Science magazine. The atoms in a superfluid are in the same quantum state, so they move coherently and cannot gradually "spin up," as does water in a rotated container. An intriguing question is whether a supersolid—formed by applying pressure to a superfluid—could combine these remarkable properties, quantum coherence and dissipationless mass flow of atoms, in a solid that still has structural order and rigidity.

In an ordinary classical crystal, all atomic motion is frozen out at absolute zero, but solid helium-4 is a quantum solid; each atom is highly delocalized in a quantum probability cloud around its equilibrium position, and as a result, atoms on neighboring sites can exchange positions and move through the solid. In 2004, Kim and Chan (5) claimed to have observed supersolidity in solid helium-4. This discovery was followed by experimental and theoretical studies suggesting that disordered glassy solids play a key role in creating the putative super-solid state.

Two reports in last week's Science journal address the origin and effects of this disorder. Hunt et al. report their observation of the onset of remarkable ultraslow dynamics on cooling samples of solid helium, which constitutes new evidence for glass-like behavior. They reveal a subtle interplay between this glassiness and the observed supersolid-like mechanical responses. Philip Anderson argues that the supersolid will still occur in a pristine crystal, but coupling to disordered regions near dislocations enhances the supersolid response. His bold hypothesis is that every solid composed of bosons will have a supersolid ground state.

Related Links
Evidence for a Superglass State in Solid 4He
A Gross-Pitaevskii Treatment for Supersolid Helium

"This is pretty cool," says Alan Migdall of the National Institute of Standards and Technology in Gaithersburg, Maryland. "I haven't seen an approach like this before." Still, he and others say it's too soon to tell whether the new method, described on page 483 in Science, will outshine techniques that generate pairs of photons entangled from "birth."

Related Link
An entanglement filter

Related Article
Ballistic spin resonance

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Control of Graphene's Properties by Reversible Hydrogenation: Evidence for Graphane

Primarily based on its atomic resolution imaging capability, the STM has had phenomenal success in the field of surface science. How can a truly surface-sensitive technique be used to measure a bulk property? The key trick applied by Weismann et al. is to exploit the wave nature of the electrons in copper and study their interference patterns on the surface caused by scattering centers in the bulk of the material. Their technique opens the door to a real-space investigation of electron propagation in materials and to the scattering of electrons at defects well below the surface.

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Seeing the Fermi Surface in Real Space by Nanoscale Electron Focusing

Science: The self-assembly of block copolymers into nanoscale features is potentially attractive as a means for patterning media in microelectronic applications. This new route to nanopatterning is gaining interest as optical lithography, the current engine of the semiconductor industry, begins to approach intrinsic technological limits while demand for higher-density features for improved data storage and computing speed continues to grow. These applications require not only regularly sized nanoscale features but also a degree of perfection of order and registry relative to other components, which have so far been elusive in self-assembled systems. In this week's issue of Science, two papers ( Graphoepitaxy of Self-Assembled Block Copolymers on Two-Dimensional Periodic Patterned Templates and Density Multiplication and Improved Lithography by Directed Block Copolymer Assembly) describe how block copolymers in conjunction with coarse templates are used to create nanoscale structures with an unprecedented level of control.

Science: Metals are solids in which conduction electrons remain mobile even at absolute zero temperature. In a semimetal, the concentration of such mobile electrons is extremely low. Whereas in a typical metal, say copper, there is roughly one itinerant electron per atom, in bismuth, the archetypal semimetal, 100,000 atoms share a single mobile electron. On the July 25 issue of Science, Li et al. report that in the presence of a strong magnetic field, this dilute electron gas orders in a way never observed in any other material.

Nature: Different material options for high-temperature superconductivity— conduction of electricity with little or no resistance at 'practical' temperatures — have arrived. Iron compounds are the latest thing.

Science: Do iron-and-arsenic superconductors work the same way as the older, inscrutable copper-and-oxygen compounds? Early evidence points both ways.

Related Physics Today article
New family of quaternary iron-based compounds superconducts at tens of kelvin (May 2008)

csmonitor.com: Scientists around the world are scrambling to unlock the secrets behind a new group of materials that act as autobahns for electricity – conducting current with virtually no wasteful resistance.

The discovery establishes a third major group of so-called high-temperature superconductors – a broad category that scientists first uncovered in 1986. Such materials hold the promise of making everything from computers to electric motors far more efficient, as scientists boost the temperature frontiers at which the materials work.

Related Physics Today article
New family of quaternary iron-based compounds superconducts at tens of kelvin May 2008

Nature News: Some experts think that a quantum computation could be plaited like a skein of string. And now they may have found the sorts of string they need, finds Liesbeth Venema.

When Alexei Kitaev published a preprint suggesting that the topological properties of quasiparticles, moving around each other and behaving as anyons, could be used as the basis for a new form of error-proof quantum computing, it seemed absurd.

“I laughed when I first read it,” recalls Nick Bonesteel, a theoretical physicist at Florida State University in Tallahassee. And there may still be some people laughing today — but at least a few of them are doing so with excited anticipation.

Related Physics Today material
Devices Based on the Fractional Quantum Hall Effect May Fulfill the Promise of Quantum Computing (October 2005)

Nature: As the great quantum physicist Werner Heisenberg — he of the uncertainty principle — made plain, in quantum mechanics, separation of the observer from the phenomenon to be observed is not possible. But in fact, the strange idea that consciousness, intelligence and the act of observation are intertwined with physical phenomena predates Heisenberg. Specifically, James Clerk Maxwell famously introduced into his studies of thermodynamics "a being whose faculties are so sharpened that he can follow every molecule in its course", such that it could identify and siphon off the hotter (faster) molecules in a gas. 'Maxwell's demon' would thus be able to extract useful work from the system, while heat is in effect transferred from a cooler to a hotter region — in clear breach of the normal direction of heat flow from hotter to cooler encapsulated in the second law of thermodynamics.

In this week's Nature, Erez and others provide a neat link between these physical curiosities, by suggesting a way to use the quantum measurement process to control a system's thermodynamics, in the spirit of Maxwell's demon. At the heart of their concept is the quantum-physical equivalent of the old adage 'a watched pot never boils'. This is the quantum Zeno effect, which states that, if you measure a quantum system often enough, it will never be able to change its state, and so will not evolve at all.

Science: Can ultracold, highly pressurized solid helium flow like the thinnest possible liquid? For 4 years, physicists have debated that question. Now, preliminary data from Robert Hallock of the University of Massachusetts (UMass), Amherst, and his team provide the most direct evidence yet for such flow.

"It's a very, very clever experiment," says Moses Chan of Pennsylvania State University in State College. But all agree it hasn't solved the mystery of solid helium.

Physics Update: A new study shows how a region of space could be rendered invisible to matter waves. In recent years the possibility of optical cloaking has become a hot topic (e.g., Science, 8 Sept 2006). Even cloaking with sound waves has been proposed. Now physicists in Xiang Zhang’s group at the University of California, Berkeley, are trying to extend the cloaking idea to atom waves (chilled atoms whose quantum wavelike properties are more important than their particle-like properties) moving through a medium.

The “medium” in question here is a concentric optical lattice, generated by standing electromagnetic waves with spatially controlled amplitudes and phases. Cloaking of an object bathed in light works by modulating the effective mass and potential of atom waves traversing the shell surrounding the object. The shell is analogous to the metamaterials (tailored materials often consisting of arrays of tiny rods and ring-shaped metal structures) used in the optical case.

One of the Berkeley researchers, Shuang Zhang says that the atom-wave equivalent of an index of refraction would be the modulation of the effective atomic mass inside the optical lattice. Zhang says that apart from cloaking, the creation of a metamaterial for atom waves might also help in focusing atom waves into tiny spot (super-lensing) or for steering particle beams at will. (Zhang et al., Physical Review Letters, 28 March 2008.

Nature: An unexpected imbalance in how particles containing the heaviest quarks decay might reveal exotic influences — and perhaps help to explain why matter, rather than antimatter, dominates the Universe.

Related Link
Difference in direct charge-parity violation between charged and neutral B meson decays (Nature)

University of Florida news: Confirming a decades-old prediction, the physicists with the CLEO collaboration say they observed a rare and extremely short-lived subatomic particle with the unusual name of “charmed-strange meson” decay into a proton and anti-neutron.

Detection of the event, which the collaboration made public Sunday, was attributed to John Yelton, a physicist at the University of Florida, one of many institutions that are part of the CLEO collaboration.

“It’s the sort of thing that, for many years, people have known should happen,” Yelton said. “What we have done is show that it does, and how often.”

Yelton said the latest result shows there remains much to be learned from collisions at lower energy in lower energy colliders. “It highlights the fact that there is still physics to be done at lower energy accelerators,” he said.

The CLEO collaboration has also submitted a paper on the discovery to the journal Physics Review Letters.

Nature: The atoms and bonds that make up complex solids can be identified chemically — a feat made possible by cleverly combining spectroscopic and structural information conveyed by electrons scattered through a thin sample.

Nature news: Atoms can be more overweight than we thought, a team of scientists in the United States has discovered.

They have sent atoms crashing into one another in a particle accelerator to create bloated versions of the elements aluminium and magnesium. The new, artificial forms of these metals have many more neutrons in their atomic nuclei than do the everyday versions1

Fert and Gruenberg helped pioneer the making of semiconductor stacks consisting of alternating thin layers of magnetic and non-magnetic atoms needed to produce the GMR effect. GMR is a prominent example of how quantum effects (a large electrical response to a tiny magnetic input) come about through confinement (the atomic layers being so thin.); that is, atoms interact differently with each other when they are confined to a tiny volume or a thin plane. All these magnetic interactions involve the spin of an electron. Spin is a quantum attribute that shouldn’t be associated too closely in the mind with the electron literally spinning (in the way that a top spins). Still more innovative technology can be expected through quantum effects depending on electrons’ spin. Most of the electronics industry is based on manipulating the charges of electrons moving through circuits. But the electrons’ spins might also be exploited to gain new control over data storage and manipulation. Spintronics is the general name for this branch of electronics.

Related Physics Today articles
Layered Magnetic Structures: History, Highlights, Applications, May 2001, page 31
Basic Research in the Information Technology Industry, Jul 2003
Magnetic Semiconductors Enable Efficient Electrical Spin Injection, April 2000, page 21
Physics Today, April 1995 (available November 1)

Related web sites
2007 Nobel Prize site
Wolf Prize announcement
Peter Gruenberg
Recent papers by Fert and Gruenberg

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Nature: Well-established models of nuclei describe properties such as shells and magic numbers. But how do these predictions stand up to scrutiny for exotic, unstable nuclei? Pretty well, according to the latest study.

AZoNano.com: Northeastern University Physics professor Sergey V. Kravchenko along with colleagues Svetlana Anissimova (Northeastern University), A Punnoose (City College if the City University of New York), AM Finkelstein (Weizmann Institute of Science, Israel) and TM Klapwijk (Delft University of Technology, Netherlands), has published an important new paper in the August issue of Nature Physics which answers a long standing question in the field of condensed matter physics.

Science: More than 20 years after the discovery of cuprate superconductors, physicists do not agree on what mechanism causes the loss of electrical resistance at temperatures as high as 160 K (known as Tc, the transition temperature). They do agree that electron pairs are crucial because they can form a condensate that flows without resistance, but the interaction that causes the pairs to form is disputed. Philip W. Andersen suggests in this week's Science that the bosonic glue most physicists believe is needed to explain the superconducting behavior is folklore rather than the result of scientific logic.

Nature: For most of its existence, a superfluid droplet leads an essentially innocuous, classical life. But intense scrutiny reveals that the birth of such droplets is a turbulent and unpredictable quantum affair.

Nature: The spins of a layer of manganese atoms on a tungsten surface form a spiral pattern with a unique turning sense. Such 'chiral magnetic order' might exist in other, similar contexts, and could have many useful applications.

News@Nature: A team of European physicists led by Anton Zeilinger of the University of Vienna, has successfully transmitted a secure quantum 'key' between two of the Canary Islands, opening the possibility of long-distance, wireless quantum cryptography.

Science: X-ray free-electron lasers promise beams that are vastly brighter and with higher energy and shorter pulses than today's scientific workhorse: synchrotron x-rays. These "hard" x-ray wavelengths—down to 0.1 nanometer—promise to reveal the structure of proteins that have eluded other techniques and nanometer-scale features in materials. Pulses as short as 100 femtoseconds or less will act as strobes to produce movies of molecular bonds breaking and forming in chemical reactions. And astrophysicists will become experimentalists, using beams 10 billion times brighter than synchrotron radiation to create the extreme state of matter believed to exist within forming stars. With U.S. and European machines in the works, Japan wants into the club reports Dennis Normile in Science.

Nature: Werner Marx and Andreas Barth have decided to revise their recently published paper on the future of high-temperature superconductivity research after complaints about their ominous conclusions. They stand by their data, they say, but add that some things could perhaps have
been better phrased.