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Metamaterial turns an insulator into a metal

 
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Southpark Fan



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PostPosted: Mon Jul 16, 2012 11:46 am    Post subject: Metamaterial turns an insulator into a metal Reply with quote

A golden antenna turns an insulator into a metal
Matthew Francis | July 16 2012 | Ars Technica


'Most normal metals are conductors from very low temperatures up to their melting point, or are insulating under all normal conditions. Vanadium dioxide (VO2) is a weird substance that can suddenly transition from an insulator to a conductor. The rapid shift in the behavior of VO2 can be induced by increasing the temperature, exposing the material to strong light, placing it in an electric field, and other stimuli. But the exact mechanism underlying the transition is unknown.'


Photo: A gold "antenna" used to enhance an oscillating electric field
Credit: Ars Technica


'The main difference between metals and insulators lies in how tightly electrons are bound to their atoms. In metals, the outermost electrons are very loosely bound and form a kind of fluid, so that individual electrons can no longer be associated with a particular atom. This fluid flows easily as an electric current under the right external stimuli. Insulators' electrons are tightly bound, and so they have extreme difficulty moving beyond their host atom.

That's why the insulator-metal transition (IMT) is strange: since the metallic or insulator character depends on the atoms, it's unusual for a single material to transition between one type of behavior and the other. However, prior studies persuasively argued that the IMT must be due to interactions between the electrons in some way.'

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Continuity



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PostPosted: Tue Jul 17, 2012 4:10 am    Post subject: Reply with quote

Fascinating material no doubt - from Wiki:

Quote:
Structure

...The precise origin of this metal to insulator transition remains controversial, and is of particular interest in condensed matter physics.

Uses

Tungsten-doped vanadium dioxide (W:VO2) with 1.9% tungsten content has been investigated for use as a "spectrally-selective" window coating to block infrared transmission and reduce the loss of building interior heat through windows. This material behaves like a semiconductor at temperatures below 29 °C, allowing more transmission, and like a conductor at higher temperatures, providing much greater reflectivity.[3][4] Varying the amount of tungsten allows regulating the phase transition temperature. However, the coating has a slight yellow-green color.[5]

Vanadium dioxide can act as an extremely fast optical shutter. The thermochromic phase transition between the transparent semiconductive and reflective conductive phase, occurring at 68 °C, can happen in times as short as 100 femtoseconds.[6]

Vanadium dioxide, especially in its nanocrystalline form, may find use in glazing applications, extremely fast optical shutters, optical modulators, infrared modulators for missile guidance systems, cameras, data storage, and other applications.

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Continuity



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PostPosted: Tue Jul 17, 2012 4:23 am    Post subject: Reply with quote

Another couple of interesting artiles about this fascinating substance:

Reversible Doping: Hydrogen Flips Switch On Vanadium Oxide

Scientists Crack Materials Mystery in Vanadium Dioxide

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Southpark Fan



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PostPosted: Fri Aug 03, 2012 7:10 am    Post subject: Reply with quote

Fascinating stuff Continuity - thks for the links!

Accelerated Electrons Bend Light The Wrong Way
Rachel Courtland | August 02, 2012 | IEEE Spectrum


'A new metamaterial, built from two semiconducting layers, has been shown to have an unprecedented ability to refract light in the wrong direction.


Credit: IEEE Spectrum

When light moves from one medium to another, the change in speed causes it to bend or refract. The refractive power of any one material is measured by its index of refraction. For naturally occurring materials, this index of refraction is positive and typically has a value of 5 or less.

Metamaterials (I do not like using Wikipedia - I apoligise for the links), which can be built in a range of ways by using, say nanoparticles or bent arrangements of wire, can bend light differently, exhibiting a property called negative refraction. They’ve been eyed for a range of applications, from invisibility cloaks to light manipulating devices that can beat the physical limitations of conventional materials. Most metamaterials have been created with negative indexes of refraction in the same rough range as naturally occurring materials (although they boast the opposite sign), says Donhee Ham at Harvard University. But, as Ham and his colleagues report today in Nature, there is a way to create "extraordinarily strong" negative refraction. The team built semiconductor devices with negative refractive indexes as low as -700, a hundred times lower than what's seen in most metamaterials, and, Ham suspects, the strongest yet seen. What's more, he says, the device can manipulate microwaves in area that’s about 1/10,000th the size of what’s needed for metamaterials that use wire-based devices like split ring antennas.'

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Southpark Fan



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PostPosted: Sat Aug 18, 2012 7:47 am    Post subject: Reply with quote

New form of carbon is so hard it can indent diamond
Aug 16, 2012 | Physics World


'A new form of carbon that is hard enough to indent diamond has been created by a team of researchers from the US and China. The new material, known as ordered amorphous carbon clusters (OACC), is structurally unique in having both crystalline and disordered elements. Created by a team led by Lin Wang of the Carnegie Institution for Science in the US, the material was made by subjecting solvated carbon-60 molecules to phenomenal pressures more than 300,000 times that of the atmosphere.


Credit: Physic World

Carbon comes in many guises, including graphite, diamond, nanotubes, graphene and charcoal. But until now, all have been classified as either crystalline – built from repeating atomic units – or amorphous, that is, lacking the long-range structural order seen in crystals. As a crystalline material composed of amorphous clusters, OACC is the first hybridized carbon structure ever seen that is part amorphous and part crystalline.'

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PostPosted: Sun Sep 16, 2012 9:13 am    Post subject: Reply with quote

'Memristors' Based On Transparent Electronics Offer Technology of the Future
Oregon State University | Sep. 14, 2012 | ScienceDaily


'The transparent electronics that were pioneered at Oregon State University may find one of their newest applications as a next-generation replacement for some uses of non-volatile flash memory, a multi-billion dollar technology nearing its limit of small size and information storage capacity.

Researchers at OSU have confirmed that zinc tin oxide, an inexpensive and environmentally benign compound, has significant potential for use in this field, and could provide a new, transparent technology where computer memory is based on resistance, instead of an electron charge.

The findings were recently published in Solid-State Electronics, a professional journal.

This resistive random access memory, or RRAM, is referred to by some researchers as a "memristor." Products using this approach could become even smaller, faster and cheaper than the silicon transistors that have revolutionized modern electronics -- and transparent as well.

Transparent electronics offer potential for innovative products that don't yet exist, like information displayed on an automobile windshield, or surfing the web on the glass top of a coffee table.'

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PostPosted: Sun Nov 11, 2012 8:25 pm    Post subject: Reply with quote

Water-Splitting Catalyst Revealed
Dexter Johnson | November 09, 2012 | IEEE Spectrum


'This detailed imaging of how photosynthesis splits water into its constituent parts has been held out as a way to help engineers more cheaply synthesize hydrogen gas to power hydrogen fuel cells—and possibly the automobiles powered by them. Research efforts to split water molecules into hydrogen gas have been taken on both by commercial entities and the academics. Perhaps this new information on the electronic structure of the water-splitting process of photosynthesis can further inform both these lines of research.'

Related: Team demonstrates new hybrid nanomaterial for power generation

Related: Conductance measurements on graphene nanoribbons tell researchers how molecular wires can be optimised

Related: First noiseless single photon amplifier

Related: Making a better invisibility cloak

Related: Touch-Sensitive, Self-Healing Artificial Material

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PostPosted: Thu May 23, 2013 7:44 pm    Post subject: Reply with quote

Material That Sorts Molecules by Shape Could Lower the Price of Gas
Kevin Bullis | May 23, 2013 | Technology Review


A hydrocarbon-sorting material could replace energy-intensive oil refining steps.

'A new material that sorts hydrocarbon molecules by shape could lower the cost of gasoline and also make the fuel safer by reducing the need for certain additives that have been linked to cancer, according to a paper in the next issue of the journal Science. Refiners typically use a material that can sort molecules by size during a key step in the refining process. To achieve a desired octane rating, this step has to be supplemented with energy-intensive distillation steps, or by the use of additives. The new material, which sorts molecules by shape rather than by size, can better differentiate between different types of hydrocarbon molecules, eliminating the distillation steps and the need for octane-enhancing additives.
...'

More: Liquefied Air Could Power Cars and Store Energy from Sun and Wind

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PostPosted: Mon Sep 30, 2013 8:11 am    Post subject: Reply with quote

Seeing Light in a New Light: Scientists Create Never-Before-Seen Form of Matter
Sep. 25, 2013 | Science Daily


Harvard and MIT scientists are challenging the conventional wisdom about light, and they didn't need to go to a galaxy far, far away to do it.

With colleagues at the Harvard-MIT Center for Ultracold Atoms, a group led by Harvard Professor of Physics Mikhail Lukin and MIT Professor of Physics Vladan Vuletic have managed to coax photons into binding together to form molecules -- a state of matter that, until recently, had been purely theoretical. The work is described in a September 25 paper in Nature.

The discovery, Lukin said, runs contrary to decades of accepted wisdom about the nature of light. Photons have long been described as massless particles which don't interact with each other -- shine two laser beams at each other, he said, and they simply pass through one another.

"Photonic molecules," however, behave less like traditional lasers and more like something you might find in science fiction -- the light saber.

"Most of the properties of light we know about originate from the fact that photons are massless, and that they do not interact with each other," Lukin said. "What we have done is create a special type of medium in which photons interact with each other so strongly that they begin to act as though they have mass, and they bind together to form molecules. This type of photonic bound state has been discussed theoretically for quite a while, but until now it hadn't been observed.

"It's not an in-apt analogy to compare this to light sabers," Lukin added. "When these photons interact with each other, they're pushing against and deflect each other. The physics of what's happening in these molecules is similar to what we see in the movies."

To get the normally-massless photons to bind to each other, Lukin and colleagues, including Harvard post-doctoral fellow Ofer Fisterberg, former Harvard doctoral student Alexey Gorshkov and MIT graduate students Thibault Peyronel and Qiu Liang couldn't rely on something like the Force -- they instead turned to a set of more extreme conditions.
...'

Related: Move Over Graphene: The Wonder Conductor of the Future May Be Stanene

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PostPosted: Tue Jul 19, 2016 9:28 am    Post subject: Reply with quote

Tiny 'Atomic Memory' Device Could Store All Books Ever Written
Charles Q. Choi | July 18, 2016 | Live Science


Quote:
A new "atomic memory" device that encodes data atom by atom can store hundreds of times more data than current hard disks can, a new study finds.

"You would need just the area of a postage stamp to write out all books ever written," said study senior author Sander Otte, a physicist at the Delft University of Technology's Kavli Institute of Nanoscience in the Netherlands.

In fact, the researchers estimated that if they created a cube 100 microns wide — about the same diameter as the average human hair — made of sheets of atomic memory separated from one another by 5 nanometers, or billionths of a meter, the cube could easily store the contents of the entire U.S. Library of Congress. [10 Technologies That Will Transform Your Life]

"Of course, these estimations are all a little silly, but in my opinion, they help to get an idea of how incredibly small this memory device really is," Otte told Live Science.

Information overload

As the world generates more data, researchers are seeking ways to store all of that information in as little space as possible. The new atomic memory devices that researchers developed can store more than 500 trillion bits of data per square inch (6.45 square centimeters) — about 500 times more data than the best commercial hard disk currently available, according to the scientists who created the new devices.

The scientists created their atomic memory device using a scanning tunneling microscope, which uses an extremely sharp needle to scan over surfaces just as a blind person would run his or her fingers over a page of braille to read it. Scanning tunneling microscope probes can not only detect atoms, but also nudge them around.

Computers represent data as 1s and 0s — binary digits known as bits that they express by flicking tiny, switch-like transistors either on or off. The new atomic memory device represents each bit as two possible locations on a copper surface; a chlorine atom can slide back and forth between these two positions, the researchers explained.

"If the chlorine atom is in the top position, there is a hole beneath it — we call this a 1," Otte said in a statement. "If the hole is in the top position and the chlorine atom is therefore on the bottom, then the bit is a 0." (Each square hole is about 25 picometers, or trillionths of a meter, deep.)

The bits are separated from one another by rows of other chlorine atoms. These rows could keep the bits in place for more than 40 hours, the scientists found. This system of packing atoms together is far more stable and reliable than atomic memory strategies that employ loose atoms, the researchers said. [How Big Is the Internet, Really?]

These atoms were organized into 127 blocks of 64 bits. Each block was labeled with a marker of holes. These markers are similar to the QR codes now often used in ads and tickets. These markers can label the precise location of each block on the copper surface.

The markers can also label a block as damaged; perhaps this damage was caused by some contaminant or flaw in the copper surface — about 12 percent of blocks are not suitable for data storage because of such problems, according to the researchers. All in all, this orderly system of markers could help atomic memory scale up to very large sizes, even if the copper surface the data is encoded on is not entirely perfect, they said.

A big step

All in all, the scientists noted that this proof-of-principle device significantly outperforms current state-of-the-art hard drives in terms of storage capacity.

As impressive as creating atomic memory devices is, Otte said that for him, "The most important implication is not at all the data storage itself."

Instead, for Otte, atomic memory simply demonstrates how well scientists can now engineer devices on the level of atoms. "I cannot, at this point, foresee where this will lead, but I am convinced that it will be much more exciting than just data storage," Otte said.

The creation of atomic-scale machinery was first suggested in 1959 by Nobel laureate physicist Richard Feynman in a famous lecture dubbed "There's Plenty of Room at the Bottom." To honor Feynman, the researchers coded 160 words from Feynman's lecture on an area 100 nanometers wide. [Mad Geniuses: 10 Odd Tales About Famous Scientists]

"Just stop and think for a moment how far we got as humans that we can now engineer things with this amazing level of precision, and wonder about the possibilities that it may give," Otte said.

Reading a block of bits currently takes about 1 minute, and rewriting a block of bits currently requires about 2 minutes, the researchers said. However, they noted that it's possible to speed up this system by making probes move faster over the surfaces of these atomic memory devices, potentially for read-and-write speeds on the order of 1 million bits per second.

Futuristic tech

Still, the researchers cautioned that atomic memory will not record data in large-scale data centers anytime soon. Currently, these atomic memory devices only work in very clean vacuum environments where they cannot become contaminated, and require cooling by liquid nitrogen to supercold temperatures of minus 321 degrees Fahrenheit (minus 196 degrees Celsius, or 77 kelvins) to prevent the chlorine atoms from jittering around.

Still, such temperatures are "easier to obtain than you may think," Otte said. "Many MRI scanners in hospitals are already kept at 4 kelvins (minus 452 degrees Fahrenheit, or minus 269 degrees Celsius) permanently, so it is not at all inconceivable that future storage facilities in data centers could be maintained at [liquid nitrogen temperatures]."

Future research will investigate different combinations of materials that may help atomic memory's "stability at higher temperatures, perhaps even room temperature," Otte said.

The scientists detailed their findings online today (07/18/2016) in the journal Nature Nanotechnology.

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