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- Transition from turbulent to nearly laminar vortex flow in superconductors with periodic pinning
Posted by Victor Moshchalkov
J. Gutierrez, A. V. Silhanek, J. Van de Vondel, W. Gillijns, and V. V. Moshchalkov
We revisit the vortex dynamics in Al thin films containing an artificial periodic array of antidots by means of electrical transport measurements. We clearly identify a turbulent to laminarlike vortex flow transition which manifests itself as a negative differential resistivity.
- Self-organized mode-locking effect in superconductor/ferromagnet hybrids
Posted by Victor Moshchalkov
J. Van de Vondel, A. V. Silhanek, V. Metlushko, P. Vavassori, B. Ilic, and V. V. Moshchalkov
The vortex dynamics in a low-temperature superconductor deposited on top of a rectangular array of micrometer size permalloy triangles is investigated experimentally. We demonstrate the spontaneous formation of two separated rows of vortices and antivortices along each line of connected triangles. The existence of a clear flux-flow regime at zero external field supports this interpretation. Strikingly, the presence of vortex-antivortex rows gives rise to a self-organized synchronized motion of vortices which manifests itself as field independent Shapiro steps in the current-voltage characteristics.
- Type-1.5 Superconductivity
Posted by Victor Moshchalkov
Victor Moshchalkov, Mariela Menghini, T. Nishio, Q. H. Chen, A.V. Silhanek, V. H. Dao, L. F. Chibotaru, N. D. Zhigadlo, and J. Karpinski
We demonstrate the existence of a novel superconducting state in high quality two-component MgB2 single crystalline superconductors where a unique combination of both type-1 and type-2 superconductor conditions is realized for the two components of the order parameter. This condition leads to a vortex-vortex interaction attractive at long distances and repulsive at short distances.
- Symmetry-Induced Giant Vortex State in a Superconducting Film with a Fivefold Penrose Array of Magnetic Pinning Centers
Posted by Victor Moshchalkov
R. B. G. Kramer, A.V. Silhanek, J. Van de Vondel, B. Raes, and V.V. Moshchalkov
A direct visualization of the flux distribution in a Pb film covering a fivefold Penrose array of Co dots is obtained by mapping the local field distribution with a scanning Hall probe microscope. Strikingly, for H = 1.6H1, interstitial and pinned vortices arrange themselves in ringlike structures (‘‘vortex corrals’’) which favor the formation of a giant vortex state at their center.
- Formation of stripelike flux patterns obtained by freezing kinematic vortices
Posted by Victor Moshchalkov
A.V. Silhanek, M.V. Milosevic, R. B. G. Kramer, G. R. Berdiyorov, J. Van de Vondel, R. F. Luccas, T. Puig, F. M. Peeters, and V.V. Moshchalkov
We visualize the formation of flux rivers resulting from a short-range attractive interaction between vortices. This dynamically induced vortex-vortex attraction results from the migration of quasiparticles out of the vortex core (kinematic vortices).
External news feeds
- How nanotechnology could keep your heart healthy
Since the heart is such a delicate and critical organ, clinicians usually opt not to intervene with the dead cells that remain after a heart attack or cardiac disease. "But we think that all heart attacks deserve some kind of treatment because it puts so much stress on the rest of the heart," said Thomas Webster, professor and chair of the Department of Chemical Engineering. Even a square centimeter of dead heart tissue can put significant strain on the rest of the heart, which has to pick up the slack, he said.
- Research improves dry lubricant used in machinery and biomedical devices
Nearly everyone is familiar with the polytetrafluoroethylene (PTFE), otherwise known as Teflon, the brand name used by the chemical company DuPont. Famous for being "non-sticky" and water repellent, PTFE is a dry lubricant used on machine components everywhere, from kitchen tools and engine cylinders to space and biomedical applications.
- Stacking 2-D materials produces surprising results
(Phys.org) â€”Graphene has dazzled scientists, ever since its discovery more than a decade ago, with its unequalled electronic properties, its strength and its light weight. But one long-sought goal has proved elusive: how to engineer into graphene a property called a band gap, which would be necessary to use the material to make transistors and other electronic devices.
- Graphene-boron mix shows promise for lithium-ion batteries
Frustration led to revelation when Rice University scientists determined how graphene might be made useful for high-capacity batteries.
- Researchers report first fully integrated artificial photosynthesis nanosystem
(Phys.org) â€”In the wake of the sobering news that atmospheric carbon dioxide is now at its highest level in at least three million years, an important advance in the race to develop carbon-neutral renewable energy sources has been achieved. Scientists with the U.S. Department of Energy (DOE)'s Lawrence Berkeley National Laboratory (Berkeley Lab) have reported the first fully integrated nanosystem for artificial photosynthesis. While "artificial leaf" is the popular term for such a system, the key to this success was an "artificial forest."
- DNA-guided assembly yields novel ribbon-like nanostructures
(Phys.org) â€”Scientists at the U.S. Department of Energy's Brookhaven National Laboratory have discovered that DNA "linker" strands coax nano-sized rods to line up in way unlike any other spontaneous arrangement of rod-shaped objects. The arrangement-with the rods forming "rungs" on ladder-like ribbons linked by multiple DNA strands-results from the collective interactions of the flexible DNA tethers and may be unique to the nanoscale. The research, described in a paper published online in ACS Nano, a journal of the American Chemical Society, could result in the fabrication of new nanostructured materials with desired properties.
- Snake's ultra-black spots may aid high-tech quest
Scientists have identified nanostructures in the ultra-black skin markings of an African viper which they said Thursday could inspire the quest to create the ultimate light-absorbing material.
- Carbon in a twirl: The science behind a self-assembled nano-carbon helix
Nanotechnology draws on the fabrication of nanostructures. Scientists have now succeeded in growing a unique carbon structure at the nanoscale that resembles a tiny twirled mustache. Their method might lead the way to the formation of more complex nano-networks. Researchers of the Electronic Properties of Materials Group at the Faculty of Physics (University of Vienna) and their international collaborators have published their results in the new open-access journal of the Nature Publishing group, Scientific Reports.
- Moth-inspired nanostructures take the color out of thin films
Inspired by the structure of moth eyes, researchers at North Carolina State University have developed nanostructures that limit reflection at the interfaces where two thin films meet, suppressing the "thin-film interference" phenomenon commonly observed in nature. This can potentially improve the efficiency of thin-film solar cells and other optoelectronic devices.
- Nanotechnology could help fight diabetes: Injectable nanogel can monitor blood-sugar levels, secrete insulin when needed
Injectable nanoparticles developed at MIT may someday eliminate the need for patients with Type 1 diabetes to constantly monitor their blood-sugar levels and inject themselves with insulin.
- Ultraresponsive magnetic nanoscavengers for next generation water purification
(Phys.org) â€”Among its many talents, silver is an antibiotic. Titanium dioxide is known to glom on to certain heavy metals and pollutants. Yet other materials do the same for salt. In recent years, environmental engineers have sought to disinfect, depollute, and desalinate contaminated water using nanoscale particles of these active materials. Engineers call them nanoscavengers. The hitch from a technical standpoint is that it is nearly impossible to reclaim the nanoscavengers once in the water.
- 40-year-old prediction confirmed: First direct proof of Hofstadter butterfly fractal observed in moire superlattices
A team of researchers from Columbia University, City University of New York, the University of Central Florida (UCF), and Tohoku University and the National Institute for Materials Science in Japan, have directly observed a rare quantum effect that produces a repeating butterfly-shaped energy spectrum, confirming the longstanding prediction of this quantum fractal energy structure, called Hofstadter's butterfly. The study, which focused on moirĂ©-patterned graphene, is published in the May 15, 2013, Advance Online Publication (AOP) of Nature.
- Catching graphene butterflies
Writing in Nature, a large international team led Dr Roman Gorbachev from The University of Manchester shows that, when graphene placed on top of insulating boron nitride, or 'white graphene', the electronic properties of graphene change dramatically revealing a pattern resembling a butterfly.
- Physicists discover a new kind of friction in the nanoworld
Whether in vehicle transmissions, hip replacements, or tiny sensors for triggering airbags: The respective components must slide against each other with minimum friction to prevent loss of energy and material wear. Investigating the friction behavior of nanosystems, scientists from the Technische Universitaet Muenchen have discovered a previously unknown type of friction that sheds new light on some previously unexplainable phenomena.
- Squishy hydrogels may be the ticket for studying biological effects of nanoparticles
(Phys.org) â€”A class of water-loving, jelly-like materials with uses ranges ranging from the mundane, such as superabsorbent diaper liners, to the sophisticated, such as soft contact lenses, could be tapped for a new line of serious work: testing the biological effects of nanoparticles now being eyed for a large variety of uses.
- Scientists discovering new uses for tiny carbon nanotubes
Nanotubes are stronger than steel and smaller than any element of silicon-based electronics. They can potentially process information faster while using less energy. The challenge has been figuring out how to incorporate these properties into useful electronic devices. Now scientists at the University of California, Riverside have discovered that by adding ionic liquidâ€”a kind of liquid saltâ€”they can modify the optical transparency of single-walled carbon nanotube films in a controlled pattern.
- Chemists demonstrate nanoscale alloys so bright they could have potential medical applications
(Phys.org) â€”Alloys like bronze and steel have been transformational for centuries, yielding top-of-the-line machines necessary for industry. As scientists move toward nanotechnology, however, the focus has shifted toward creating alloys at the nanometer scaleâ€”producing materials with properties unlike their predecessors.
- Microgravity experiment gets funding, may go to International Space Station
A microgravity experiment designed at The Methodist Hospital Research Institute will be funded by The Center for the Advancement of Science in Space (CASIS) to fly aboard the International Space Station U.S. National Laboratory.
- Researchers develop synthetic HDL cholesterol nanoparticles
(Phys.org) â€”Atherosclerosis, a buildup of cellular plaque in the arteries, remains one of the leading causes of death globally. While high-density lipoprotein, or HDL, the so-called good cholesterol, is transferred to the liver for processing, low-density lipoprotein, or LDL, builds up in the arteries in the form of plaque.
- Bovine blood keeps gold nanoparticles stable
(Phys.org) â€”A protein from cow blood has the remarkable ability to keep gold nanoparticles from clumping in a solution. The discovery could lead to improved biomedical applications and contribute to projects that use nanoparticles in harsh environments.
- Solar panels as inexpensive as paint? It's possible due to new research
(Phys.org) â€”Most Americans want the U.S. to place more emphasis on developing solar power, recent polls suggest. A major impediment, however, is the cost to manufacture, install and maintain solar panels. Simply put, most people and businesses cannot afford to place them on their rooftops.
- Team observes real-time charging of a lithium-air battery
One of the most promising new kinds of battery to power electric cars is called a lithium-air battery, which could store up to four times as much energy per pound as today's best lithium-ion batteries. But progress has been slow: The nature of the electrochemical reactions as these batteries are charged remains poorly understood.
- New insight into early growth of solid thin films
(Phys.org) â€”The foundation of many modern electronic devices, such as computer chips, are thin films â€“ nanoscale-thickness layers of one material grown on the surface of another. As consumers continue to demand products that are sleeker and faster, understanding the evolution of thin-film growth will help scientists learn to tailor thin films for new technologies.
- How to overcome the oxide barrier
(Phys.org) â€”Researchers at Pacific Northwest National Laboratory have uncovered the characteristics of a low-resistance electrical contact to strontium titanate, SrTiO3, an important prototypical oxide semiconductor. Oxides are likely to be important materials in next-generation electronic devices, and they need to be extremely small. Getting electrical signals into and out of oxide semiconductors is hard because a large energy barrier typically develops at the junction with metal contacts. Metal contacts are required to get electricity into and out of a semiconductor device in much the same way that jumper cables are needed to transfer power from a healthy car battery to a dead battery. This work shows how to eliminate this barrier while keeping the contact area extremely small, at the nanometer level.
- Graphene joins the race to redefine the ampere
A new joint innovation by the National Physical Laboratory (NPL) and the University of Cambridge could pave the way for redefining the ampere in terms of fundamental constants of physics. The world's first graphene single-electron pump (SEP), described in a paper today in Nature Nanotechnology, provides the speed of electron flow needed to create a new standard for electrical current based on electron charge.
- Nano-breakthrough: Solving the case of the herringbone crystal
Leading nanoscientists created beautiful, tiled patterns with flat nanocrystals, but they were left with a mystery: Why did some sets of crystals arrange themselves in an alternating, herringbone style? To find out, they turned to experts in computer simulation at the University of Michigan and the Massachusetts Institute of Technology.
- Perfectly doped quantum dots yield colors to dye for
(Phys.org) â€”Quantum dots are tiny nanocrystals with extraordinary optical and electrical properties with possible uses in dye production, bioimaging, and solar energy production. Researchers at the University of Illinois at Chicago have developed a way to introduce precisely four copper ions into each and every quantum dot.
- New magnetic graphene may revolutionise electronics
Researchers from IMDEA-Nanociencia Institute and from Autonoma and Complutense Universities of Madrid (Spain) have managed to give graphene magnetic properties. The breakthrough, published in the journal Nature Physics, opens the door to the development of graphene-based spintronic devices, that is, devices based on the spin or rotation of the electron, and could transform the electronics industry.
- Scientists enhance light emission in 2D semiconductors by a factor of 100
(Phys.org) â€”The mention of a two-dimensional material with excellent electrical and optical properties may first bring to mind graphene. However, this description also fits another class of materials called transition metal dichalcogenides (TMDs). Although TMDs in bulk form have been studied for decadesâ€”before graphene was even discoveredâ€”only recently they have been isolated to monolayers. With recent advances in nanomaterial characterization, scientists have recognized the potential of monolayer TMDs in applications such as LEDs, optical energy conversion, and other 2D optoelectronics technologies.
- Researchers fine-tune the sensitivity of nano-chemical sensor
Researchers have discovered a technique for controlling the sensitivity of graphene chemical sensors.