Superconductivity in orbit: Scientists find new path to loss-free electricity

Superconductivity in orbit: Scientists find new path to loss-free electricity: "For the first time, we obtained direct experimental evidence of the subtle changes in electron orbitals by comparing an unaltered, non-superconducting material with its doped, superconducting twin," said Brookhaven Lab physicist and project leader Yimei Zhu...

The Brookhaven researchers used a technique called quantitative convergent beam electron diffraction (CBED) to reveal the orbital clouds with subatomic precision...

The researchers first examined the electron clouds of non-superconducting samples of barium iron arsenic. The CBED data revealed that the arsenic atoms—placed above and below the iron in a sandwich-like shape (see image)—exhibited little shift or polarization of valence electrons. However, when the scientists transformed the compound into a superconductor by doping it with cobalt, the electron distribution radically changed.

A grand unified theory of exotic superconductivity?

A grand unified theory of exotic superconductivity?: In the current paper, Davis and Lee propose and demonstrate within a simple model that antiferromagnetic electron interactions can drive both superconductivity and the various intertwined phases across different families of high-Tc superconductors. These intertwined phases and the emergence of superconductivity, they say, can be explained by how the antiferromagnetic influence interacts with another variable in their theoretical description, namely the "Fermi surface topology..."


"The basic assumption of our theory is that when we rip away all the complicated intertwined phases, underneath there is an ordinary metal," said Lee. "It is the antiferromagnetic interactions in this metal that make the electrons want to form the various states. The complex behavior originates from the system fluctuating from one state to another, e.g., from superconductor to charge density waves to nematic order. It is the antiferromagnetic interaction acting on the underlying simple metal that causes all the complexity."

First fully computer-designed superconductor | KurzweilAI

First fully computer-designed superconductor | KurzweilAI: Several years ago, Kolmogorov, then at Oxford University, began studying boron-based materials, which have complex structures and a wide range of applications. He developed an automated computational tool to identify previously unknown stable crystal structures. His “evolutionary” algorithm emulates nature, meaning it favors more stable materials among thousands of possibilities.

The search revealed two promising compounds in a common iron-boron system, which came as a surprise. Moreover, a graduate student’s calculations indicated that one of them should be a superconductor at an unusually high temperature of 15–20 Kelvin for the “conventional” type of superconductivity.

Man-made material pushes the bounds of superconductivity (March 3, 2013)

Man-made material pushes the bounds of superconductivity (March 3, 2013): The researchers can tailor the material, which seamlessly alternates between metal and oxide layers, to achieve extraordinary superconducting properties — in particular, the ability to transport much more electrical current than non-engineered materials...

The researchers' new material is composed of 24 layers that alternate between the pnictide superconductor and a layer of the oxide strontium titanate. Creating such systems is difficult, especially when the arrangement of atoms, and chemical compatibility, of each material is very different.

Yet, layer after layer, the researchers maintained an atomically sharp interface...

The new material also has improved current-carrying capabilities. As they grew the superlattice, the researchers also added a tiny bit of oxygen to intentionally insert defects every few nanometers in the material. These defects act as pinning centers to immobilize tiny magnetic vortices that, as they grow in strength in large magnetic fields, can limit current flow through the superconductor. "If the vortices move around freely, the energy dissipates, and the superconductor is no longer lossless," says Eom. "We have engineered both vertical and planar pinning centers, because vortices created by magnetic fields can be in many different orientations."

Close look at iron-based superconductor advances theory

Close look at iron-based superconductor advances theory: Surprisingly, however, when the material is "underdoped" with not quite enough cobalt to create superconductivity, an ordinary electric current moves easily along only one axis of the crystal—call it "lengthwise"—but encounters high resistance moving crosswise. This effect increases with the amount of cobalt doping, and may offer a clue to how superconductivity works.

Scanning tunneling microscope (STM) images of the electronic structure of the material in this underdoped state reveal an array of tiny, elongated groups of electrons in an unusual energy state, aligned with the long axis of the crystal, that act as barriers to electrons moving crosswise.

Breakthrough iron-based superconductors set new performance records

Breakthrough iron-based superconductors set new performance records: These custom-grown materials carry tremendous current under exceptionally high magnetic fields—an order of magnitude higher than those found in wind turbines, magnetic resonance imaging (MRI) machines, and even particle accelerators. The results— published online January 8 in the journal Nature Communications—demonstrate a unique layered structure that outperforms competing low-temperature superconducting wires while avoiding the high manufacturing costs associated with high-temperature superconductor (HTS) alternatives...

The scientists synthesized this novel film of iron, selenium, and tellurium to push existing performance parameters. In addition to the raw materials being relatively inexpensive, the synthesis process itself can be performed at just half the temperature of cuprate-based HTS alternatives, or approximately 400 degrees Celsius.

Scientists developed a high-performance superconducting material by mixing iron and selenium

Scientists developed a high-performance superconducting material by mixing iron and selenium: Physicists describe how they have synthesized a new material that belongs to the iron-selenide class of superconductors, called LixFe2Se2(NH3)y... This material displays promising superconducting transition temperatures of 44 Kelvins (K) at ambient pressure...

Modern-Day Alchemy Has Iron Working Like Platinum - NYTimes.com

Modern-Day Alchemy Has Iron Working Like Platinum - NYTimes.com: Dr. Chirik’s work involves dissolved catalysts, which are mixed into the end product. The molecules of the catalyst dissipate during the reaction. For instance, a solution containing platinum is used to make silicone emulsifiers, compounds that in turn feed products like makeup, cookware and glue. Tiny amounts of the expensive metal are scattered in all these things; your jeans, for instance, contain unrecoverable particles of platinum...

Dr. Chirik’s chemistry essentially wraps an iron molecule in another, organic molecule called a ligand. The ligand alters the number of electrons available to form bonds. It also serves as a scaffold, giving the molecule shape. “Geometry is really important in chemistry,” Dr. Hartings said. Dr. Chirik’s “ligands help the iron to be in the right geometry to help these reactions along.”

Ferroelectric memristors may lead to brain-like computers

Ferroelectric memristors may lead to brain-like computers: In a new study, a team of researchers from France, the UK, and Japan has demonstrated that a device called a ferroelectric tunnel junction (FTJ) that experiences voltage-controlled resistance variation represents a new class of memristor. Due to the FTJ's quasi-continuous resistance variations exceeding two orders of magnitude, along with its rapid 10-ns operation speed, the device could one day serve as the basic hardware of neuromorphic computational architectures, or computers that function like brains...

"We have conceptualized, designed and realized a completely new type of memristor that performs as well as classical ionic memristors, but operates through an electronic mechanism," coauthor Manuel Bibes, a CNRS research scientist, told Phys.org. "While this should have clear advantages in terms of reproducibility, the key breakthrough is that our ferroelectric memristor behaves according to well-established physical models. This allows a precise understanding of the memristive response, and also opens the door for engineering memristive functions on-demand."

Superconductivity associated with fractal structure of nanoscale electron lines

Superconductivity associated with fractal structure of nanoscale electron lines:  Said Dahmen, “We decided to make histograms of the sizes of these regions and compare them with predictions from various models. We found they agreed with those from models that also had fingery regions in the bulk of the material—the agreement was striking.”

Carlson explained, “We noticed that the pattern of orientations of the nanoscale lines doesn’t depend on the scale of the image. The pattern looks the same whether we view the entire image, or whether we view smaller and smaller pieces of it—the pattern is fractal.

“Every fractal has its own set of characteristic numbers, as unique as a fingerprint. You might imagine that the characteristic numbers for a fractal which is happening only on the surface would be different from the characteristic numbers for a fractal which really originates from deep inside the material.

“When we studied the characteristic numbers of this fractal, we discovered telltale signs in its fingerprint that indicate this is not just a surface fractal.  Rather, it is coming from deep inside the material. We are seeing a 3-D fractal, which then intersects the surface of the material.”

Iron-based high-temp superconductors show unexpected electronic asymmetry

Iron-based high-temp superconductors show unexpected electronic asymmetry: Prior studies have shown that as HTS materials are cooled, they pass through a series of intermediate electronic phases before they reach the superconducting phase. To help see these "phase changes" at a glance, physicists like Nevidomskyy often use graphs called "phase diagrams" that show the particular phase an HTS will occupy based on its temperature and chemical doping.
"With this new evidence, it is clear that the nematicity exists all the way into the superconducting region and not just in the vicinity of the magnetic phase, as it had been previously understood," said Nevidomskyy, in reference to the line representing the boundary of the nematic order. "Perhaps the biggest discovery of this study is that this line extends all the way to the superconducting phase."
He said another intriguing result is that the phase diagram for the barium iron arsenide bears a striking resemblance to the phase diagram for copper-based high-temperature superconductors.

Theory Explains the Quantum Weirdness of Exotic Materials | Wired Science | Wired.com

Theory Explains the Quantum Weirdness of Exotic Materials | Wired Science | Wired.com: Physicists have now developed a mathematical theory that describes how collective quantum mechanical weirdness leads to the strange properties of these materials. While previous work has focused on each individual system, the new theory unites the behavior for many materials, including magnets, superfluids, and neutron star matter...
Murayama and his graduate student, Haruki Watanabe, showed that the behavior of these materials hinges on a phenomenon known as spontaneous symmetry breaking...

Iron-based superconductors exhibit s-wave symmetry

Iron-based superconductors exhibit s-wave symmetry: In conventional superconductors, the Cooper pairs have s-wave pairing symmetry, which takes the shape of a sphere. In contrast, Cooper pairs in the cuprate family of high-temperature superconductors exhibit d-wave pairing symmetry, which looks a bit like a four-leaf clover. The leaves, or lobes, are areas where the superconducting gap is finite. At the points where two leaves join, known as nodes, the superconducting gap goes to zero.
However, iron-based superconductors do not fall nicely into either of these two categories...

They discovered a signature that could not have originated from a d-wave pairing – a striking difference from the cuprate family.
This finding, the first measurement of its kind, provides solid experimental evidence that iron-based superconductors fall into the regime of s-wave pairing symmetry seen in conventional superconductors, and suggests that both nodal and nodeless gaps could arise from the same mechanism. This could lead to a unified theoretical framework for both phenomena, making the research an important step toward unveiling the mechanism of iron-based superconductivity.

Scientists switch mouse's genes off and on with radio waves

Scientists switch mouse's genes off and on with radio waves: Friedman and his colleagues coated iron oxide nanoparticles with antibodies that bind to a modified version of the temperature-sensitive ion channel TRPV1, which sits on the surface of cells. They injected these particles into tumours grown under the skins of mice, then used the magnetic field generated by a device similar to a miniature magnetic-resonance-imaging machine to heat the nanoparticles with low-frequency radio waves. In turn, the nanoparticles heated the ion channel to its activation temperature of 42 °C. Opening the channel allowed calcium to flow into cells, triggering secondary signals that switched on an engineered calcium-sensitive gene that produces insulin. After 30 minutes of radio-wave exposure, the mice's insulin levels had increased and their blood sugar levels had dropped...
Even better, the researchers have already developed a way to achieve similar, albeit weaker, results without having to inject nanoparticles at all. They have developed cells that can grow their own required nanoparticles, meaning there would be no need to give patients strange chemicals or molecules.

Using Magnetic Bacteria to Construct the Biocomputer of the Future | Popular Science

Using Magnetic Bacteria to Construct the Biocomputer of the Future | Popular Science: The bacterium Magnetospirilllum magneticum is a naturally occurring microorganism that lives in underwater environs, using its natural magnetism to swim up and down the Earth’s magnetic field lines in search of oxygen. But when they eat iron, special proteins generate tiny crystals of the mineral magnetite within the bacteria, imbuing them with a tiny piece of one of the more magnetic natural materials on the planet.
By feeding the bacteria iron and manipulating the way they colonize, the researchers think they can essentially grow tiny magnets that could serve as components in the minuscule hard drives of the future. Whereas it’s very difficult to make very small magnets and shape them so that they can serve as memory devices, these proteins and the bacteria in which they reside can be coaxed into doing all the hard work, creating the magnetic material and churning out regularly-shaped blocks of it.
Moreover, the team has been working to produce tiny electrical wires that allow the exchange of information through cell membranes, allowing for nanoscale communication inside of a computer made up of biological cells.

Atomic-scale visualization of electron pairing in iron superconductors

Atomic-scale visualization of electron pairing in iron superconductors: Two scientists working with Davis, Milan P. Allan of Brookhaven, Cornell, and the University of Saint Andrews (where Davis also teaches) and Andreas W. Rost of Cornell and St. Andrews - the lead authors on the paper - figured out how to do the experiments and identified an iron-based material (lithium iron arsenide) in which to test the predictions.
Their method, multi-band Bogoliubov quasiparticle scattering interference, found the "signature" predicted by the theorists:
"The strength of the 'glue' holding the pairs together is different on the different bands, and on each band it depends on the direction that the electrons are traveling - with the pairing usually being stronger in a given direction than at 45° to that direction," Davis said.
"This is the first experimental evidence direct from the electronic structure in support of the theories that the mechanism for superconductivity in iron-based superconductors is due primarily to magnetic interactions," he said.

Pigeons may ‘hear’ magnetic fields : Nature News & Comment

Pigeons may ‘hear’ magnetic fields : Nature News: Individual neurons in birds' brains can relay crucial information about Earth’s magnetic field...

For their latest research, the subject of today's Science paper, Wu and Dickman restrained seven homing pigeons (Columba livia) and placed them in a dark room. A magnetic field was created to cancel Earth’s field, and the researchers then monitored the birds’ brain activity while creating and rotating carefully controlled artificial magnetic fields around the pigeons.

The authors found that vestibular neurons — which are linked to balance systems in the inner ear — fired differentially in response to alterations in the field’s direction, intensity and polarity, and that these cells were especially sensitive to the bandwith that covers Earth’s geo-magnetic field...

“I would say now there are three potential places where magnetoreceptors may rest...”  These are the beak, the eyes and the ears.

Superconductor breaks high-temperature record : Nature News & Comment

Superconductor breaks high-temperature record : Nature News : Under normal pressure, iron selenide superconducts up to about 30 K, and Sun's team expected that raising the pressure would disrupt this. The researchers squeezed a single crystal of the material, measuring 100 micrometres in diameter and 50 micrometres thick, between two diamond-tipped anvils. At first, they found exactly what they predicted: superconductivity stopped as the pressure approached 10 gigapascals.

But as they increased the pressure above 11.5 GPa the sample began to superconduct again. “Pressure-induced re-emergence of superconductivity has been not found in any families of high-temperature superconductors.” says Sun. Furthermore, at pressures of about 12.5 GPa, the sample could superconduct at temperatures up to 48 K — setting a new record for iron-selenide superconductors1.

Scientists blast iron with lasers, and it disappears from X-rays

Scientists blast iron with lasers, and it disappears from X-rays:  Scientists took two thin sheets of the material and held it in place with carbon, which is invisible to X-rays. They placed two platinum mirrors to either side of the iron sheets. They then fired a beam of low-energy X-rays into the set-up. The beam was reflected by the platinum mirrors back and forth again and again. Trapped, it set up a standing wave in the sandwich of equipment...
When one sheet of iron was at a node, and one sheet was at an antinode (the peak or the trough), another, higher energy x-ray was shot through the entire contraption. The x-ray moved through them without interacting with either sheet of iron...

Scientists learn the secret of a famous anti-superconductor

Scientists learn the secret of a famous anti-superconductor: The flip from conductor to insulator, at minus 150 degrees Celsius, discovered by Evert Verwey in 1939, has puzzled scientists ever since. Recently, though, a team from the University of Edinburgh was able to peer inside a crystal of magnetite by aiming an X-ray beam at it. The crystal was half the diameter of a human hair. The team dropped the temperature of the crystal, and saw that the entire structure rearranged itself when brought down to negative 150 degrees. The iron atoms, until then happy to let the electrons proceed, suddenly shifted into organized groups of three, pinning the electron between them. The electrons were trapped, and unable to flow, stopping all current through the magnetite.