Artificial Photosynthesis Moves A Step Closer

Source:

http://www.sciencedaily.com/releases/2008/04/080428085757.htm

ScienceDaily (Apr. 28, 2008) — Imagine a technology that would not only provide a green and renewable source of electrical energy, but could also help scrub the atmosphere of excessive carbon dioxide resulting from the burning of fossil fuels. That’s the promise of artificial versions of photosynthesis, the process by which green plants have been converting solar energy into electrochemical energy for millions of years. To get there, however, scientists need a far better understanding of how Nature does it, starting with the harvesting of sunlight and the transporting of this energy to electrochemical reaction centers.

Graham Fleming, a physical chemist who holds joint appointments with the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) and the University of California (UC) at Berkeley, is the leader of an ongoing effort to discover how plants are able to transfer energy through a network of pigment-protein complexes with nearly 100-percent efficiency. In previous studies, he and his research group used a laser-based technique they developed called two-dimensional electronic spectroscopy to track the flow of excitation energy through both time and space. Now, for the first time, they’ve been able to connect that flow to energy-transferring functions by providing direct experimental links between atomic and electronic structures in pigment-protein complexes.
“To fully understand how the energy-transfer system in photosynthesis works, you can’t just study the spatial landscape of these pigment-protein complexes, you also need to study the electronic energy landscape. This has been a challenge because the electronic energy landscape is not confined to a single molecule but is spread out over an entire system of molecules,” Fleming said. “Our new 2D electronic spectroscopy technique has enabled us to move beyond the imaging of structures and to start imaging functions. This makes it possible for us to examine the crucial aspects of the energy-transfer system that enable it to work the way it does.
Fleming and his group report on a study of the energy-transferring functions within the Fenna-Matthews-Olson (FMO) photosynthetic light-harvesting protein, a pigment-protein complex in green sulfur bacteria that serves as a model system because it consists of only seven well-characterized pigment molecules.
“The optical properties of bacteriochlorophyll pigments are well understood, and the spatial arrangement of the pigments in FMO is known, but this has not been enough to understand how the protein as a whole responds to light excitation,” said Read. “By polarizing the laser pulses in our 2D electronic spectroscopy set-up in specific ways, we were able to visualize the direction of electronic excitation states in the FMO complex and probe the way individual states contribute to the collective behavior of the pigment-protein complex after broadband excitation.”
Fleming has compared 2D electronic spectroscopy to the early super-heterodyne radios, where an incoming high frequency radio signal was converted by an oscillator to a lower frequency for more controllable amplification and better reception. In 2D electronic spectroscopy, a sample is sequentially flashed with light from three laser beams, delivered in femtosecond timescale bursts, while a fourth beam serves as a local oscillator to amplify and phase-match the resulting spectroscopic signals.
“By providing femtosecond temporal resolution and nanometer spatial resolution, 2D electronic spectroscopy allows us to simultaneously follow the dynamics of multiple electronic states, which makes it an especially useful tool for studying photosynthetic complexes,” Fleming said. “Because the pigment molecules within protein complexes have a fixed orientation relative to each other and each absorbs light polarized along a particular molecular axis, the use of 2D electronic spectroscopy with polarized laser pulses allows us to follow the electronic couplings and interactions (between pigments and the surrounding protein) that dictate the mechanism of energy flow. This suggests the possibility of designing future experiments that use combinations of tailored polarization sequences to separate and monitor individual energy relaxation pathways.”
In all photosynthetic systems, the conversion of light into chemical energy is driven by electronic couplings that give rise to collective excitations - called molecular or Frenkel excitons (after Russian physicist Yakov Frenkel) - which are distinct from individual pigment excitations. Energy in the form of these molecular excitons is transferred from one molecule to the next down specific energy pathways as determined by the electronic energy landscape of the complex. Polarization-selective 2D electronic spectroscopy is sensitive to molecular excitons - their energies, transition strengths, and orientations - and therefore is an ideal probe of complex functions.
“Using specialized polarization sequences that select for a particular cross-peak in a spectrum allows us to probe any one particular electronic coupling even in a system containing many interacting chromophores,” said Read. “The ability to probe specific interactions between electronic states more incisively should help us better understand the design principles of natural light-harvesting systems, which in turn should help in the design of artificial light-conversion devices.”
The paper, entitled “Visualization of Excitonic Structure in the Fenna-Matthews-Olson Photosynthetic Complex by Polarization-Dependent Two-Dimensional Electronic Spectroscopy,” was co-authored by Elizabeth Read, along with Gabriela Schlau-Cohen, Gregory Engel, Jianzhong Wen and Robert Blankenship. It was published in the Biophysical Journal.
Adapted from materials provided by DOE/Lawrence Berkeley National Laboratory.

Fausto Intilla - www.oloscience.com

Exotic Quantum State Of Matter Discovered

Source:

http://www.sciencedaily.com/releases/2008/04/080424130707.htm

ScienceDaily (Apr. 25, 2008) — A team of scientists from Princeton University has found that one of the most intriguing phenomena in condensed-matter physics -- known as the quantum Hall effect -- can occur in nature in a way that no one has ever before seen.

Writing in the April 24 issue of Nature, the scientists report that they have recorded this exotic behavior of electrons in a bulk crystal of bismuth-antimony without any external magnetic field being present. The work, while significant in a fundamental way, could also lead to advances in new kinds of fast quantum or "spintronic" computing devices, of potential use in future electronic technologies, the authors said.
"We had the right tool and the right set of ideas," said Zahid Hasan, an assistant professor of physics who led the research and propelled X-ray photons at the surface of the crystal to find the effect. The team used a high-energy, accelerator-based technique called "synchrotron photo-electron spectroscopy."
And, Hasan added, "We had the right material."
The quantum Hall effect has only been seen previously in atomically thin layers of semiconductors in the presence of a very high applied magnetic field. In exploring new realms and subjecting materials to extreme conditions, the scientists are seeking to enrich the basis for understanding how electrons move.
Robert Cava, the Russell Wellman Moore Professor of Chemistry and a co-author on the paper, worked with members of his team to produce the crystal in his lab over many months of trial-and-error. "This is one of those wonderful examples in science of an intense, extended collaboration between scientists in different fields," said Cava, also chair of the Department of Chemistry.
"This remarkable experiment is a major home run for the Princeton team," said Phuan Ong, a Princeton professor of physics who was not involved in the research. Ong, who also serves as assistant director of the Princeton Center for Complex Materials, added that the experiment "will spark a worldwide scramble to understand the new states and a major program to manipulate them for new electronic applications."
Electrons, which are electrically charged particles, behave in a magnetic field, as some scientists have put it, like a cloud of mosquitoes in a crosswind. In a material that conducts electricity, like copper, the magnetic "wind" pushes the electrons to the edges. An electrical voltage rises in the direction of this wind -- at right angles to the direction of the current flow. Edwin Hall discovered this unexpected phenomenon, which came to be known as the Hall effect, in 1879. The Hall effect has become a standard tool for assessing charge in electrical materials in physics labs worldwide.
In 1980, the German physicist Klaus von Klitzing studied the Hall effect with new tools. He enclosed the electrons in an atom-thin layer, and cooled them to near absolute zero in very powerful magnetic fields. With the electrons forced to move in a plane, the Hall effect, he found, changed in discrete steps, meaning that the voltage increased in chunks, rather than increasing bit by bit as it was expected to. Electrons, he found, act unpredictably when grouped together. His work won him the Nobel Prize in physics in 1985.
Daniel Tsui (now at Princeton) and Horst Stormer of Bell Laboratories did similar experiments, shortly after von Klitzing's. They used extremely pure semiconductor layers cooled to near absolute zero and subjected the material to the world's strongest magnet. In 1982, they suddenly saw something new. The electrons in the atom-thin layer seemed to "cooperate" and work together to form what scientists call a "quantum fluid," an extremely rare situation where electrons act identically, in lock-step, more like soup than as individually spinning units.
After a year of thinking, Robert Laughlin, now at Stanford University, devised a model that resembled a storm at sea in which the force of the magnetic wind and the electrons of this "quantum fluid" created new phenomena -- eddies and waves -- without being changed themselves. Simply put, he showed that the electrons in a powerful magnetic field condensed to form this quantum fluid related to the quantum fluids that occur in superconductivity and in liquid helium.
For their efforts, Tsui, Stormer and Laughlin won the Nobel Prize in physics in 1998.
Recently, theorist Charles Kane and his team at the University of Pennsylvania, building upon a model proposed by Duncan Haldane of Princeton, predicted that electrons should be able to form a Hall-like quantum fluid even in the absence of an externally applied magnetic field, in special materials where certain conditions of the electron orbit and the spinning direction are met. The electrons in these special materials are expected to generate their own internal magnetic field when they are traveling near the speed of light and are subject to the laws of relativity.
In search of that exotic electron behavior, Hasan's team decided to go beyond the conventional tools for measuring quantum Hall effects. They took the bulk three-dimensional crystal of bismuth-antimony, zapped it with ultra-fast X-ray photons and watched as the electrons jumped out. By fine-tuning the X-rays, they could directly take pictures of the dancing patterns of the electrons on the edges of the sample. The nature of the quantum Hall behavior in the bulk of the material was then identified by analyzing the unique dancing patterns observed on the surface of the material in their experiments.
Kane, the Penn theorist, views the Princeton work as extremely significant. "This experiment opens the door to a wide range of further studies," he said.
The images observed by the Princeton group provide the first direct evidence for quantum Hall-like behavior without external magnetic fields.
"What is exciting about this new method of looking at the quantum Hall-like behavior is that one can directly image the electrons on the edges of the sample, which was never done before," said Hasan. "This very direct look opens up a wide range of future possibilities for fundamental research opportunities into the quantum Hall behavior of matter."
Other researchers on the paper include graduate students David Hsieh, Andrew Lewis Wray, YuQi Xia and postdoctoral fellows Dong Qian and Yew San Hor. The team members are in the departments of physics and chemistry, and are members of the Princeton Center for Complex Materials. They used facilities at the Lawrence Berkeley Laboratory in Berkeley, Calif., and the University of Wisconsin's Synchrotron Radiation Center in Stoughton, Wis.
This work was supported by U.S. Department of Energy and the National Science Foundation.
Adapted from materials provided by Princeton University.

Fausto Intilla - www.oloscience.com

What Happens When You Pop A Quantum Balloon?

Source:

http://www.sciencedaily.com/releases/2008/04/080417155913.htm

ScienceDaily (Apr. 20, 2008) — When a tiny, quantum-scale, hypothetical balloon is popped in a vacuum, do the particles inside spread out all over the place as predicted by classical mechanics".
The question is deceptively complex, since quantum particles do not look or act like air molecules in a real balloon. Matter at the infinitesimally small quantum scale is both a wave and a particle, and its location cannot be fixed precisely because measurement alters the system.
Now, theoretical physicists at the University of Southern California and the University of Massachusetts Boston have proven a long-standing hypothesis that quantum-scale chaos exists ... sort of.
Writing in the April 17 edition of Nature, senior author Maxim Olshanii reported that when an observer attempts to measure the energies of particles coming out of a quantum balloon, the interference caused by the attempt throws the system into a final, "relaxed" state analogous to the chaotic scattering of air molecules.
The result is the same for any starting arrangement of particles, Olshanii added, since the act of measuring wipes out the differences between varying initial states.
"It's enough to know the properties of a single stationary state of definite energy of the system to predict the properties of the thermal equilibrium (the end state)," Olshanii said.
The measurement -- which must involve interaction between observer and observed, such as light traveling between the two -- disrupts the "coherent" state of the system, Olshanii said.
In mathematical terms, the resulting interference reveals the final state, which had been hidden in the equations describing the initial state of the system.
"The thermal equilibrium is already encoded in an initial state," Olshanii said. "You can see some signatures for the future equilibrium. They were already there but more masked by quantum coherences."
The finding holds implications for the emerging fields of quantum computing and quantum information theory, said Paolo Zanardi, an associate professor of physics studying quantum information at USC.
In Zanardi's world, researchers want to prevent coherent systems from falling into the chaos of thermal equilibrium.
"Finding such 'unthermalizable' states of matter and manipulating them is exactly one of those things that quantum information/computation folks like me would love to do," Zanardi wrote. "Such states would be immune from 'decoherence' (loss of quantum coherence induced by the coupling with environment) that's still the most serious, both conceptually and practically, obstacle between us and viable quantum information processing."
Zanardi and a collaborator introduced the notion of "decoherence-free" quantum states in 1997. Researchers such as Zanardi and Daniel Lidar, associate professor of chemistry, among others, have helped make USC a major center for the study of quantum computing.
Olshanii and his co-authors, postdoctoral researchers Marcos Rigol and Vanja Dunjko, developed their theory of quantum thermal equilibrium at USC and completed their work at the University of Massachusetts Boston.
Their research was funded by the National Science Foundation and the Office of Naval Resarch.
Adapted from materials provided by University of Southern California, via EurekAlert!, a service of AAAS.

Fausto Intilla - www.oloscience.com

Prototype Terahertz Imager Promises Advances In Biochemistry

Source:

http://www.sciencedaily.com/releases/2008/04/080415164314.htm

ScienceDaily (Apr. 15, 2008) — Researchers at the National Institute of Standards and Technology (NIST) have demonstrated a new imaging system that detects naturally occurring terahertz radiation with unprecedented sensitivity and resolution. The technology may become a new tool chemical and biochemical analyses ranging from early tumor detection to rapid and precise identification of chemical hazards for homeland security instruments.
Terahertz radiation falls between microwaves and infrared radiation on the electromagnetic spectrum, with frequencies from about 300 million cycles per second to about 3 trillion cycles per second. Biological and chemical samples naturally emit characteristic signatures of terahertz radiation, but detecting and measuring them is a unique challenge because the signals are weak and absorbed rapidly by the atmosphere.
The NIST prototype imager, described in detail for the first time in a new paper,* uses an exquisitely sensitive superconducting detector combined with microelectronics and optics technologies to operate in the terahertz range. The NIST system has its best resolution centered around a frequency of 850 gigahertz, a "transmission window" where terahertz signals can pass through the atmosphere. The system can detect temperature differences smaller than half a degree Celsius, which helps to differentiate between, for example, tumors and healthy tissue.
The heart of the system is a tiny device that measures incoming terahertz radiation by mixing it with a stable internal terahertz signal. This mixing occurs in a thin-film superconductor, which changes temperature upon the arrival of even a minute amount of radiation energy. The slight frequency difference between the two original terahertz signals produces a more easily detected microwave frequency signal.
NIST developed the device and antenna, combined with an amplifier on a chip smaller than a penny, in collaboration with the University of Massachusetts. Called a hot electon bolometer (HEB), the technology is sensitive enough to detect the weak terahertz signals naturally emitted by samples, eliminating the need to generate terahertz radiation to actively illuminate the samples. This greatly reduces complexity and minimizes safety concerns. In addition, the NIST "mixer" system delivers more information by detecting both the magnitude and phase (the point where each individual wave begins) of the radiation.
Because passively emitted signals are so weak, the current system takes about 20 minutes to make a single 40 x 40 pixel image. NIST researchers are working on an improved version that will scan faster and operate at two frequencies at once. Future systems also should be able to achieve better spatial resolution.
* E. Gerecht, D. Gu, L. You and S. Yngvesson. Passive heterodyne hot electron bolometer imager operating at 850 GHz. Forthcoming in IEEE Transactions on Microwave Theory and Techniques.
Adapted from materials provided by National Institute of Standards and Technology.

Fausto Intilla - www.oloscience.com

Innovative Composite Opens Terahertz Frequencies To Many Applications

Source:

http://www.sciencedaily.com/releases/2008/04/080415185016.htm

ScienceDaily (Apr. 16, 2008) — A frequency-agile metamaterial that for the first time can be tuned over a range of frequencies in the so-called "terahertz gap" has been engineered by a team of researchers from Boston College, Los Alamos National Laboratory and Boston University.

The team incorporated semiconducting materials in critical regions of tiny elements -- in this case metallic split-ring resonators -- that interact with light in order to tune metamaterials beyond their fixed point on the electromagnetic spectrum, an advance that opens these novel devices to a broader array of uses, according to findings published in the online version of the journal Nature Photonics.
"Metamaterials no longer need to be constructed only out of metallic components," said Boston College Physicist Willie J. Padilla, the project leader. "What we've shown is that one can take the exotic properties of metamaterials and combine them with the unique prosperities of natural materials to form a hybrid that yields superior performance."
Padilla and BC graduate student David Shrekenhamer, along with Hou-Tong Chen, John F. O'Hara, Abul K Azad and Antoinette J. Tayler of Los Alamos National Laboratory, and Boston University's Richard D. Averitt formed a single layer of metamaterial and semiconductor that allowed the team to tune terahertz resonance across a range of frequencies in the far-infrared spectrum.
The team's first-generation device achieved 20 percent tuning of the terahertz resonance to lower frequencies -- those in the far-infrared region --addressing the critical issue of narrow band response typical of all metamaterial designs to date.
Constructed on the micron-scale, metamaterials are composites that use unique metallic contours in order to produce responses to light waves, giving each metamaterial its own unique properties beyond the elements of the actual materials in use.
Within the past decade, researchers have sought ways to significantly expand the range of material responses to waves of electromagnetic radiation -- classified by increasing frequency as radio waves, microwaves, terahertz radiation, infrared radiation, visible light, ultraviolet radiation, X-rays and gamma rays. Numerous novel effects have been demonstrated that defy accepted principles.
"Metamaterials demonstrated negative refractive index and up until that point the commonly held belief was that only a positive index was possible," said Padilla. "Metamaterials gave us access to new regimes of electromagnetic response that you could not get from normal materials."
Prior research has shown that because they rely on light-driven resonance, metamaterials experience frequency dispersion and narrow bandwidth operation where the centre frequency is fixed based on the geometry and dimensions of the elements comprising the metamaterial composite. The team believes that the creation of a material that addresses the narrow bandwidth limitations can advance the use of metamaterials.
Enormous efforts have focused on the search for materials that could respond to terahertz radiation, a scientific quest to find the building blocks for devices that could take advantage of the frequency for imaging and other applications.
Potential applications could lie in medical imaging or security screening, said Padilla. Materials undetectable through x-ray scans -- such as chemicals, biological agents, and certain explosives -- can provide a unique "fingerprint" when struck by radiation in the far-infrared spectrum. Metamaterials like the one developed by the research team will facilitate future devices operating at the terahertz frequency of the electromagnetic spectrum.
In addition to imaging and screening, researchers and high-tech companies are probing the use of terahertz in switches, modulators, lenses, detectors, high bit-rate communications, secure communications, the detection of chemical and biological agents and characterization of explosives, according to Los Alamos National Laboratory.
Adapted from materials provided by Boston College, via EurekAlert!, a service of AAAS.

Fausto Intilla - www.oloscience.com

Artificial Lightning: Laser Triggers Electrical Activity In Thunderstorm For The First Time

Source: http://www.sciencedaily.com/releases/2008/04/080414082517.htm

ScienceDaily (Apr. 14, 2008) — A team of European scientists has deliberately triggered electrical activity in thunderclouds for the first time, according to a new paper in the latest issue of Optics Express, the Optical Society's (OSA) open-access journal. They did this by aiming high-power pulses of laser light into a thunderstorm.

At the top of South Baldy Peak in New Mexico during two passing thunderstorms, the researchers used laser pulses to create plasma filaments that could conduct electricity akin to Benjamin Franklin's silk kite string. No air-to-ground lightning was triggered because the filaments were too short-lived, but the laser pulses generated discharges in the thunderclouds themselves.
"This was an important first step toward triggering lightning strikes with laser beams," says Jérôme Kasparian of the University of Lyon in France. "It was the first time we generated lighting precursors in a thundercloud." The next step of generating full-blown lightning strikes may come, he adds, after the team reprograms their lasers to use more sophisticated pulse sequences that will make longer-lived filaments to further conduct the lightning during storms.
Triggering lightning strikes is an important tool for basic and applied research because it enables researchers to study the mechanisms underlying lightning strikes. Moreover, triggered lightning strikes will allow engineers to evaluate and test the lightning-sensitivity of airplanes and critical infrastructure such as power lines.
Pulsed lasers represent a potentially very powerful technology for triggering lightning because they can form a large number of plasma filaments -- ionized channels of molecules in the air that act like conducting wires extending into the thundercloud. This is such a simple concept that the idea of using lasers to trigger lightning strikes was first suggested more than 30 years ago. But scientists have not been able to accomplish this to date because previous lasers have not been powerful enough to generate long plasma channels. The current generation of more powerful lasers, like the one developed by Kasparian's team, may change that.
Kasparian and his colleagues involved in the Teramobile project, an international program initiated by National Center for Scientific Research (CNRS) in France and the German Research Foundation (DFG), built a powerful mobile laser capable of generating long plasma channels by firing ultrashort laser pulses. They chose to test their laser at the Langmuir Laboratory in New Mexico, which is equipped to measure atmospheric electrical discharges. Sitting at the top of 10,500-foot South Baldy Peak, this laboratory is in an ideal location because its altitude places it close to the high thunderclouds.
During the tests, the research team quantified the electrical activity in the clouds after discharging laser pulses. Statistical analysis showed that their laser pulses indeed enhanced the electrical activity in the thundercloud where it was aimed--in effect they generated small local discharges located at the position of the plasma channels.
The limitation of the experiment, though, was that they could not generate plasma channels that lived long enough to conduct lightning all the way to the ground. The plasma channels dissipated before the lightning could travel more than a few meters along them. The team is currently looking to increase the power of the laser pulses by a factor of 10 and use bursts of pulses to generate the plasmas much more efficiently.
Lightning strikes have been the subject of scientific investigation dating back to the time of Benjamin Franklin, but despite this, remain not fully understood. Although scientists have been able to trigger lightning strikes since the 1970s by shooting small rockets into thunderclouds that spool long wires connected to the ground, typically only 50 percent of rocket launches actually trigger a lightning strike. The use of laser technology would make the process quicker, more efficient and cost-effective and would be expected to open a number of new applications.
Kasparian conducted the research with his colleagues at CNRS, the University of Lyon, the University of Geneva, École Polytechnique and ENSTA in Palaiseau, France, the Free University of Berlin and the Dresden-Rossendorf Research Center as part of the Teramobile project. This work was funded jointly by the CNRS, DFG, the French and German ministries of foreign affairs, Agence Nationale de la Recherche, Fonds national suisse de la recherche scientifique, and the Swiss Secrétariat d'État à l'Éducation et à la Recherche.
Paper: "Electric events synchronized with laser filaments in thunderclouds," Jérôme Kasparian et al, Optics Express, Vol. 16, Issue 8, April 14, 2008, pp. 5757-63; abstract at http://www.opticsexpress.org/abstract.cfm?id=157189.
Adapted from materials provided by Optical Society of America, via EurekAlert!, a service of AAAS.

Fausto Intilla - www.oloscience.com

Newly Discovered Fundamental State Of Matter, A Superinsulator, Has Been Created

Source:

http://www.sciencedaily.com/releases/2008/04/080408160614.htm

ScienceDaily (Apr. 9, 2008) — Superinsulation may sound like a marketing gimmick for a drafty attic or winter coat. But it is actually a newly discovered fundamental state of matter created by scientists at the U.S. Department of Energy's Argonne National Laboratory in collaboration with several European institutions. This discovery opens new directions of inquiry in condensed matter physics and breaks ground for a new generation of microelectronics.

Led by Argonne senior scientist Valerii Vinokur and Russian scientist Tatyana Baturina, an international team of scientists from Argonne, Germany, Russia and Belgium fashioned a thin film of titanium nitride which they then chilled to near absolute zero. When they tried to pass a current through the material, the researchers noticed that its resistance suddenly increased by a factor of 100,000 once the temperature dropped below a certain threshold. The same sudden change also occurred when the researchers decreased the external magnetic field.
Like superconductors, which have applications in many different areas of physics, from accelerators to magnetic-levitation (maglev) trains to MRI machines, superinsulators could eventually find their way into a number of products, including circuits, sensors and battery shields.
If, for example, a battery is left exposed to the air, the charge will eventually drain from it in a matter of days or weeks because the air is not a perfect insulator, according to Vinokur. "If you pass a current through a superconductor, then it will carry the current forever; conversely, if you have a superinsulator, then it will hold a charge forever," he said.
"Titanium nitride films, as well as films prepared from some other materials, can be either superconductors or insulators depending on the thickness of the film," Vinokur said. "If you take the film which is just on the insulating side of the transition and decrease the temperature or magnetic field, then the film all of a sudden becomes a superinsulator."
Scientists could eventually form superinsulators that would encapsulate superconducting wires, creating an optimally efficient electrical pathway with almost no energy lost as heat. A miniature version of these superinsulated superconducting wires could find their way into more efficient electrical circuits.
Titanium nitride's sudden transition to a superinsulator occurs because the electrons in the material join together in twosomes called Cooper pairs. When these Cooper pairs of electrons join together in long chains, they enable the unrestricted motion of electrons and the easy flow of current, creating a superconductor. In superinsulators, however, the Cooper pairs stay separate from each other, forming self-locking roadblocks.
"In superinsulators, Cooper pairs avoid each other, creating enormous electric forces that oppose penetration of the current into the material," Vinokur said. "It's exactly the opposite of the superconductor," he added.
The theory behind the experiment stemmed from Argonne's Materials Theory Institute, which Vinokur organized six years ago in the laboratory's Materials Science Division. The MTI hosts a handful of visiting scholars from around the world to perform cutting-edge research on the most pressing questions in condensed matter physics. Upon completion of their tenure at Argonne, these scientists return to their home institutions but continue to collaborate on the joint projects. The MTI attracts the world's best condensed matter scientists, including Russian "experimental star" Tatyana Baturina, who, according to Vinokur, "became a driving force in our work on superinsulators."
Scientists from the Institute of Semiconductor Physics in Novosibirsk, Russia, Regensburg and Bochum universities in Germany and Interuniversity Microelectronics Centre in Leuven, Belgium, also participated in the research.
The research appears in the April 3 issue of Nature.
Adapted from materials provided by DOE/Argonne National Laboratory.

Fausto Intilla
www.oloscience.com