Science: The rise of nanotechnology is garnering much attention for its ability to construct objects with individual atoms and molecules, at a scale roughly a billion times smaller than the objects we encounter in our everyday lives. In parallel to nanotechnology's often astonishing achievements, scientists have started to build a capacity to do useful work on an even more minute scale. During the past decade, chemists and physicists have begun a fabrication process at the scale of the atomic nuclei. It is an emergent means of producing, in sufficient quantities, "designer" atomic nuclei, which are new, rare isotopes with unusual numbers of neutrons or protons, or unusual decay modes (1). There are several reasons why a latent demand exists within the scientific community for new isotopes. One is that the properties of particular isotopes often hold the key to understanding some aspect of nuclear science. Another is that the rate of certain nuclear reactions involving rare isotopes can be important for modeling astronomical objects. Finally, the pursuit of ever more exotic isotopes sometimes advances basic understanding of the nuclear landscape, along with unexpected areas of application.
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: After 20 years of hard labour, squeezed states — light and matter whose quantum fluctuations have been arduously suppressed below standard levels of quantum noise — are coming of age and are ripe for application.
Nature News: How does our classical world emerge from the counterintuitive principles of quantum theory? Can we even be sure that the world doesn't 'go quantum' when no one is watching? Philip Ball talks to the theorists and experimentalists trying to find out
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: A particle-like object with a quarter of an electron's charge is the latest find in a hotbed of quantum-physical experimentation, the fractional quantum Hall fluid. Its significance is more than esoteric.
The Post Chronicle: Physicists Create Superinsulators by Staff U.S. and European scientists have discovered a fundamental state of matter that they say opens new directions of inquiry in condensed matter physics. via The Post Chronicle
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.
New York Times: IBM scientists have used the tuning fork in the atomic force microscope, which measures the interaction between the tip and the atom, to calculate the force needed to nudge one atom. About one-130-millionth of an ounce of force pushes a cobalt atom across a smooth, flat piece of platinum. Pushing the same atom along a copper surface is easier, just one-1,600-millionth of an ounce of force
Nova: In preparation for the launch of NPR's new series, absolute zero, Peter Tyson asks a number of physicists if you can't get colder than 0 on the Kelvin scale, is there a corresponding maximum possible temperature?
New Scientist: A paper in Nature Physics suggests that a desktop synchrotron particle accelerator could soon be able to freeze-frame the frenetic motion of atoms and molecules. An international team of physicists led by Dino Jaroszynski of Strathclyde University in Scotland have built a prototype light source, which they claim can be upgraded to produce intense, ultra-short pulses of X-rays. Synchrotrons are in great demand because their intense X-ray beams have so many uses, from analysing biological molecules to etching electronic components and seeing inside microscopic fossils.
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.
Science: The often dramatic effects of particle irradiation on the properties of materials have been recognized and studied for over 60 years. These effects can be detrimental (as in structural materials degradation in nuclear reactors) or beneficial (as in the ion beam processing of semiconductors for the microelectronics industry). However, the microscopic processes that underlie these effects are not entirely understood, limiting researchers' ability to predict the consequences of irradiation. The reports in this week's issue of Science highlight the limits of knowledge about nanometer-sized dislocation loops in materials. The results should stimulate additional research to better understand these phenomena and to use the unique diffusion behavior to pattern materials at the nanoscale.
Science: The often dramatic effects of particle irradiation on the properties of materials have been recognized and studied for over 60 years. These effects can be detrimental (as in structural materials degradation in nuclear reactors) or beneficial (as in the ion beam processing of semiconductors for the microelectronics industry). However, the microscopic processes that underlie these effects are not entirely understood, limiting researchers' ability to predict the consequences of irradiation. The reports in this week's issue of Science highlight the limits of knowledge about nanometer-sized dislocation loops in materials. The results should stimulate additional research to better understand these phenomena and to use the unique diffusion behavior to pattern materials at the nanoscale.
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
Nature: The behaviour of ferromagnetic and ferroelectric materials in a magnetic or electric field makes them easy to spot. But for their more recently discovered counterpart, ferrotoroidic materials, things become complex.
Various:
Albert Fert of the Université Paris-Sud, Orsay, France and Peter Grünberg of the Forschungszentrum Jülich, Germany have won the 2007 Nobel Prize in physics for the discovery of giant magnetoresistance, or GMR for short. GMR is the process whereby a weak magnetic field, such as that of an oriented domain on the surface of a computer hard drive can, when the proper read head is brought nearby, trigger a large change in electrical resistance, thus “reading” the data vested in the magnetic orientation. This is the heart of modern hard drive technology and makes possible the immense hard-drive data storage industry. Earlier this year the two physicists won the Wolf Prize for the same research.
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
Related news stories
Magnetic Effect Nets a Nobel, Science
Physics of Hard Drives Wins Nobel, New York Times
Magnetic Effect Nets a Nobel, Science
Reuters
Physics Nobel Goes to German, Frenchman, Wired News
Disk technology takes Nobel Prize, BBC
Europeans Win Nobel Prize for Physics, NPR
A little magnetism wins physics Nobel, The Australian
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.
Reuters: Imagine cramming 30,000 full-length movies into a gadget the size of an iPod.
Scientists at IBM said on Thursday they had moved closer to such a feat by learning how to steer single atoms in a way that could create building blocks for ultra-tiny storage devices.
Houston Chronicle: The $1.4 billion Spallation Neutron Source facility, though still powering up, has established a new mark as the world's most powerful accelerator-based source of neutrons for scientific research.
The Oak Ridge National Laboratory announced Thursday that the SNS's neutron beam reached 183 kilowatts on Aug. 11, surpassing the 163-kilowatt record held by the ISIS facility at Rutherford Appleton Laboratory near Oxford, England.
Although the capacity of the ISIS facility is being doubled, Oak Ridge officials said their accelerator is designed to produce up to 10 times more neutrons than now.
Nature: In order to form a glass by cooling a liquid, the normal process of solid crystallization must be bypassed. Achieving that for a pure metal had seemed impossible — until pressure was applied to liquid germanium
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.
Science: In quantum physics, decoherence is a catch-all term that usually implies degradation of the purity of a quantum state. Over the past few decades it has been used as a guide to understand the loss of the two-body coherence called entanglement, which is an intrinsically quantum effect. In this context, it is relevant to fundamental questions such as: Why is the world mostly classical when we believe quantum theory provides all of the governing principles? The answer lies in the critical role of "largeness"; simply put, larger bodies lose coherence more quickly. This is the essential ingredient in producing nearly instantaneous decay of entanglement between two large bodies or between a large body and a small one. The role of largeness is seen when decoherence occurs increasingly faster with the size of the environment. Preservation of coherence is important in maintaining steady behavior of quantum systems whose coordinated action is critical, for example, among the working units of quantum computers when they become available.
A small body (spin, photon, atom, exciton, quantum dot, Cooper pair, etc.), on the other hand, can continue to behave as a quantum mechanical unit, even if not macroscopically entangled. A topic that remains open in almost all decoherence discussions, however, is the preservation or destruction of two-body quantum coherence when both bodies are small. For example, it has been predicted only recently that the one-body and two-body responses to a noisy environment can follow surprisingly different pathways to complete decoherence. Experimental entry into this new domain is needed, and impressive results are now reported on page 579 of this week's Science magazine. The researchers have devised an elegantly clean way to check and to confirm the existence of so-called "entanglement sudden death," a two-body disentanglement that is novel among known relaxation effects because it has no lifetime in any usual sense--that is, entanglement terminates completely after a finite interval, without a smoothly diminishing long-time tail.
Science: Like a prisoner trapped behind the wall of a fortress, an electron faces a huge barrier in escaping the confines of an atom. Yet when hit by a burst of intense light, it can set itself free in just a few hundred attoseconds (10-18 s), thanks to a quantum-mechanical phenomenon known as tunneling. In essence, it seeps through the barrier--the binding energy that normally holds it in place. Now, for the first time, scientists have seen this blindingly fast escape act happen in real time.
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.
Continue reading "Superconductivity researchers complain about paper" »
|
|
|
