Physics

Ceramic Pottery Reveals an Ancient Geomagnetic Field Spike

The magnetic field surrounding Earth is constantly fluctuating in strength.

Credit: NASA’s Scientific Visualization Studio

More than 2,500 years ago in the ancient Near East, the Earth’s geomagnetic field was going gangbusters. During the late eighth century B.C., a new study finds, the magnetic field that surrounds the planet was temporarily 2.5 times stronger than it is today.

Researchers know about these fluctuations thanks to the bureaucracy of Judah, an ancient kingdom situated around what is now Jerusalem. Pottery jugs from between the eighth and second centuries B.C. bear administrative stamps that changed with the political situation. Unbeknown to the people firing these jugs, the act of heating locked information about the Earth’s geomagnetic field into minerals present in the clay. Because the stamps provide precise information about when the pots were fired, the study allows a detailed look at geomagnetic changes over 600 years.

“This was the system of the king in Jerusalem to be able to collect tax efficiently,” study author Erez Ben-Yosef, an archaeologist at Tel Aviv University, said of the stamps. “We are actually benefiting from a good bureaucratic system, the ancient IRS.” [7 Ways the Earth Changes in the Blink of an Eye]

The Earth is surrounded by a magnetic field that arises from the motion of iron in the liquid outer core. Direct observation of the field has been possible for only about 180 years, Ben-Yosef told Live Science. In that time, the field has weakened by about 10 percent, he said. Some researchers think the field might be in the process of flipping, so that magnetic north becomes magnetic south and vice versa.

The new study reveals much faster changes in intensity. There was a spike in intensity during the late eighth century B.C., culminating in a rapid decline after about 732 B.C., Ben-Yosef and his colleagues reported today (Feb. 13) in the journal Proceedings of the National Academy of the Sciences. In a mere 31 years beginning in the year 732 B.C., there was a 27 percent decrease in the strength of the magnetic field, the researchers found. From the sixth century B.C. to the second century B.C., the field was generally stable, with a slight gradual decline.

“Our research shows that the field is very fluctuating,” Ben-Yosef said. “It fluctuates quite rapidly, so there is nothing to worry about,” as far as the current decline, he said. (This doesn’t mean that the magnetic field isn’t going to flip in the near future; the new study looked at only strength of the field, not directionality. The findings do suggest that there’s no reason to worry that a 10 percent decline in the field strength over more than a century is abnormal, Ben-Yosef said.)

At least in the Levant, that is. All of the pottery in the study came from this region, which encompasses what is now Syria, Jordan, Israel, Palestine, Lebanon and nearby areas. That means researchers can’t be sure whether the same fluctuations were happening elsewhere. Because the scientists also don’t know for sure the precise locations within the Levant where the pottery was fired, they can’t say anything about the direction of the geomagnetic field at the time, only its strength. [Photos: Ancient Burial and Metal Tool from Southern Levant]

The clays in ceramic pots contain ferromagnetic minerals, or minerals containing iron. When the clays are heated, the electrons in these minerals align according to the Earth’s magnetic field — imagine a series of iron filings lining up in arcs around a bar magnet. Once cooled, the magnetic patterns are locked in for good. The same process occurs when lava cools, so researchers can also detect changes in the magnetic field by studying volcanic rocks.

A stamped pottery handle from the Israel settlement called Ramat Rahel. The magnetic minerals used in the pottery were sealed in during heating and are revealing the history of Earth's magnetic field.

A stamped pottery handle from the Israel settlement called Ramat Rahel. The magnetic minerals used in the pottery were sealed in during heating and are revealing the history of Earth’s magnetic field.

Credit: Courtesy of Oded Lipschits

Understanding the ancient magnetic field has implications for many fields of research, Ben-Yosef said. Archaeologists would like to develop a new system so they could look at the magnetic properties of heated materials and date them according to what the magnetic field was doing at the time. Earth scientists want to better understand the deep structures in the core that create the magnetic field. Atmospheric scientists want to understand the interactions of the magnetic field with cosmic radiation. Biologists are interested in cosmic radiation, too: Because the magnetic field protects the planet from damaging cosmic rays, Earth owes its flourishing life to the existence of the geomagnetic field.

“This is related to various different phenomena, from biology, Earth sciences, geophysics, atmospheric sciences and archaeology,” Ben-Yosef said.

The researchers are now trying to expand their study of this time period to see if the fluctuations they observed were a regional phenomenon, or more widespread.

Physicists Forge Impossible Molecule That Chemists Failed To Make

 

There’s a bunch of physicists out there that are feeling a little bit pleased with themselves right now, and no wonder – they may have just made all of chemistry redundant. Okay, that’s not really true, but they’ve certainly beat chemistry researchers at their own game.

You see, a team of IBM physicists have managed to forge a new type of molecule, named “triangulene”, that chemistry researchers have been long hoping to synthesize themselves. This suggests that physical processes can be used to make molecules that are essentially impossible to make any other way.

This particular molecule is, unsurprisingly, triangular shaped. Triangular-shaped molecules are fairly rare due to a phenomenon known as “ring strain.” The tight angles of their molecular bonds mean that they are unstable and highly reactive, and don’t last long in a wide range of environments.

Triangulene has been hypothesized to exist by chemistry acolytes for several years now, as a single-atom layer of carbon with the triangular shape being formed from smaller hexagon forms – but no conventional chemical process seemed to be able to create a stable version of it.

Enter IBM, who decided to use a device that could manipulate atoms on an electron scale. First, as reported in the journal Nature Nanotechnology, they nabbed a precursor molecule from chemists in the UK. This molecule looks a lot like triangulene, but it came with two additional hydrogen atoms.

A sketch of triangulene imposed onto the image of the real deal. IBM Research

They placed this precursor on a range of copper and insulating plates, and used a combination of carbon monoxide and gold to probe the molecule – on the smallest of scales – using a unique atomic imaging device.

This device had previously been used to look at weird molecules like olympicene, one that’s shaped like the official logo of the Olympics. Although the images are blurry, individual atomic bonds can be seen.

The device uses changing voltages to “poke” around the molecule by interacting directly with its electrons. The interaction allows the researchers to view its intricate structure, but the team wondered if they could also use it to actually change the chemistry of the molecule itself.

Using some precisely-aimed, set-voltage “bolts,” they managed to remove the two additional hydrogen atoms, and the precursor molecule transformed into the fabled triangulene. It lasted for four days before reverting back to a more stable form – long enough to prove its existence.

“Triangulene is the first molecule that we’ve made that chemists have tried hard, and failed, to make already,” Leo Gross, who led the IBM team at the firm’s laboratories in Zurich, told Nature.

Far from just trouncing cutting-edge chemistry, the team noted that the two free electrons left over from the physical manipulation could “spin” in two separate directions. This is a key feature of molecules used in quantum computing, in that this type of molecule could have one segment of it representing a “0” and the other a “1”.

By being able to represent both states at the same time, more digital information could be stored on a system made of these molecules than ever before. That, of course, explains why IBM is so interested in the forging of triangulene.

So they didn’t just score a victory over chemistry, but one for the future of quantum computing. That’s pretty damn impressive.

These new molecules could be a vital component of future quantum computers. Jurik Peter/Shutterstock

If you want to be a modern day alchemist, then, forget Breaking Bad – have a look at Cosmos instead.

Your Electricity Company Fears This Man

your-electricity-company-fears-this-man

As we documented in a previous article, electricity is the key to unleash world democracy and freedom,

“It’s well known that many wars are fought over resources, many times oil and other energy bases. Electricity is arguably the most essential staple for human survival; because with enough electricity, water can literally be extracted from thin air, which can then be used to plant and water crops.

With enough electricity, nearly all of humanity’s needs can be met.

Centralized energy, like most of us have now, is inherently dangerous to a free society. It can fluctuate, prices can be raised, and grids can be shut down or get damaged by natural disasters. The move toward localized production of electricity, then, is a move towards freedom, security, and democracy. Autonomous energy production is the precursor to an autonomous free society. The secondary effect of increased use of renewable energy is, of course, cleaner air and less pollution. We have all the reasons in the world to support this exciting new development.”

Our previous article pointed out the strides that some countries are taking to make the move toward solar and other sustainable energies. Now, an even more exciting development has been made in the most unlikely of places: an obscure home work shop in Virginia known privately as the “box full of creative chaos”.

Doug Coulter of Floyd, Virginia, lives in the woods in what he calls a “libertarian communism”community where he spends much of his life inventing and innovation in his home work shop.

What Doug has developed can be a game changer when it comes to providing the world’s electricity. He claims that,

“If this works, I’m about to anger several trillion dollar a year businesses.”

These businesses include gas and electric utilities and Big Oil companies.

Doug claims to be on the verge of cracking what has stumped scientists for decades: nuclear fusion. Doug runs an open source forum for scientists and engineers, where he got much of the research needed to crack this priceless problem. He says that once his nuclear fusion reactor is complete, it too will be open source so that anyone living anywhere will have access to the technology. Watch this video to see what he is up to:

 

Astronomers have spotted a black hole so ravenous, it’s pushing the limits of physics

The Universe’s hungriest black hole.

 

Astronomers have discovered a giant black hole that’s so hungry, it’s been gorging on a star for more than a decade – more than 10 times longer than any stellar meal detected before.

Not only is this by far the largest meal a black hole has been seen consuming, but the feast has been going on so long that scientists aren’t quite sure how it’s been sustained without bending the laws of physics. And the answer could tell us how black holes in the early days of the Universe grew more massive than we’ve been able to explain.

When a star gets too close to a black hole, the black hole’s immense gravitational force can rip the star apart – an event known as a tidal disruption event (TDE).

We’ve seen plenty of these TDE’s in the past, thanks to the distinct X-ray flare they produce. After the black hole destroys a star, it flings some of its contents into space at high speeds, and devours the rest, growing larger and blasting out a super hot flare of X-ray radiation in the process.

But most TDEs are short-lived affairs, which is why the new observation is so surprising.

“We have witnessed a star’s spectacular and prolonged demise,” said lead researcher Dacheng Lin from the University of New Hampshire in Durham.

“Dozens of tidal disruption events have been detected since the 1990s, but none that remained bright for nearly as long as this one.”

In fact, that feast has been going on for so long, it’s pushing the limits of physics – the star being consumed has consistently surpassed something called the Eddington limit, which is the maximum luminosity a star can achieve before it’s no longer stable.

The idea is that if a star is pushing out enough radiation to get this bright, then gravity should barely be able to hold it together. And for that reason we’ve never really been able to understand how supermassive black holes at the centre of many galaxies, including our Milky Way, grew as big as they are.

This record-breaking hungry black hole is nicknamed XJ1500+0154, and exists at the core of a small galaxy about 1.8 billion light-years away.

It was spotted by a trio of satellites – NASA’s Chandra X-ray observatory and Swift satellite, as well as the European Space Agency’s XMM-Newton.

The satellites were hunting for TDEs when they stumbled across the incredibly bright flare emitted by XJ1500+0154 back in 2005.

They’ve been observing it ever since, and although it appears the meal is now winding up, the team’s evidence suggests that the black hole was consuming the star’s material for well over 10 years.

That means this is either the most massive star we’ve ever seen get caught up in a TDE, or it’s the first time we’ve seen a smaller star get completely torn apart.

“For most of the time we’ve been looking at this object, it has been growing rapidly,” said one of the researchers, James Guillochon from the Harvard-Smithsonian Centre for Astrophysics.

“This tells us something unusual – like a star twice as heavy as our Sun – is being fed into the black hole.”

The fact that we now have early evidence that black holes can eat something so massive – and grow so ginormous as a result – opens up a while new world of possibilities when it comes to black holes.

We need to keep in mind that the research has only been published on the pre-print site arXiv.org for the physics community to pore over before it’s submitted to a peer-reviewed journal, so we need to wait for independent validation of the results before we get too carried away.

Importantly, if confirmed, this observation could help explain how supermassive black holes were able to get about a billion times more massive than our Sun in the early days of the Universe – something researchers have struggled to explain.

“This event shows that black holes really can grow at extraordinarily high rates,” said team member Stefanie Komossa of China’s QianNan Normal University for Nationalities.

“This may help understand how precocious black holes came to be.”

The team predicts that XJ1500+0154’s feeding supply should be greatly reduced in the next decade, causing the black hole to fade in X-ray brightness and disappear from the satellites’ view.

Whether or not that happens remains to be seen, but astronomers will be watching the black hole closely.

You can read the full paper here.

Lab-created Metallic Hydrogen, If Legit, Could Revolutionize Physics

science, hydrogen

Harvard researchers announced they have been able to compress liquid hydrogen into a metal. HARVARD UNIVERSITY/YOUTUBE

Back in 1935, physicists Eugene Wigner and Hillard Bell Huntington of Princeton University predicted that if subjected to sufficiently intense pressure, hydrogen would become a solid metal. For the past several decades, scientists in a few elite labs around the world have been trying to accomplish just that, bombarding hydrogen with lasers and electrical pulses, and trying to squeeze it between diamonds.

It’s not just curiosity that drives them. If metallic hydrogen could be manufactured and remain stable at room temperatures, it might be an amazingly useful material. For one thing, scientists believe that it would be a superconductor, capable of allowing electrons to flow through it without any energy loss. And when heated, it would release a huge amount of energy, giving it the potential to be a game-changing propellant for rockets.

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But one downside to metallic hydrogen? Nobody’s been able to actually produce it — that is, apparently, until now. Harvard University researchers believe that they have created metallic hydrogen for the first time in the laboratory. In an article published in the journal Science, natural science professor Isaac Silvera and research fellow Ranga Dias describe compressing hydrogen at low temperatures between specially treated synthetic diamond anvils, and observing it transition through stages — from transparent to black, and eventually to a substance that reflects light. “The properties are those of an atomic metal,” they conclude.

Corresponding author Silvera didn’t respond to an email, but in a Harvard YouTube video, he says: “We have made a new material. It’s a material that never has existed on Earth before.”

 

Others also see the discovery as momentous.

“This paper is likely to be one of the most important ones in physics for several decades. It solves (experimentally) a major outstanding problem,” says Jeffrey M. McMahon, an assistant professor of physics at Washington State University not involved in the research, via email. “This is especially the case if metallic hydrogen exhibits the remarkable properties expected.” He says that metallic hydrogen could turn out to be “potentially the most powerful rocket fuel known.”

To create the substance, Silvera and Dias began by compressing liquid hydrogen — the element liquefies when cooled to minus 423 degrees Fahrenheit (minus 253 degrees Celsius) — in an anvil made from two synthetic diamonds. Then they turned a steel screw to exert more and more pressure upon the liquid hydrogen.

At a pressure of about 2 million times that of Earth’s atmosphere, the hydrogen was transparent. But once they doubled the force to 4 million atmospheres — more intense than the pressure inside Earth’s core — the hydrogen turned opaque and black. Tightening the screw even further, the hydrogen sample reflected about 90 percent of the light that was shined upon it.

The researchers used diamond anvils to compress molecular hydrogen. R. DIAS AND I.F. SILVERA/HARVARD UNIVERSITY

The Harvard scientists’ finding comes more than 80 years after metallic hydrogen was first imagined. “It has taken so long because the pressure at which it becomes metallic is higher than was originally thought by Wigner and Huntingdon,” explains University of Illinois professor David M. Ceperley, an expert in condensed matter physics, via email. “At pressures about 300 [atmospheres], diamonds become very susceptible to cracking, especially when hydrogen is present. Many other experimentalists are surprised that Dias and Silvera were able to go up to the pressures they report successfully.”

Ceperley cautions that the discovery will need to be validated by additional research. “Even the Harvard group has not repeated it yet,” he says. “They need to verify that what is in their cell is pure hydrogen and that the gasket material did not get dissolved in there making it metallic. They need to measure other properties than just optical reflectivity.”

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But in a recent article in the journal Nature, some scientists expressed skepticism about the discovery, saying that they wanted to see additional proof that metallic mercury actually had been produced. Rivera told The New York Times he plans to perform additional measurements on the hydrogen, using a process called Raman scattering, which uses laser light. He also plans to take the sample to the U.S. government’s Argonne National Laboratory in Illinois, where it will be probed with X-rays.

Ceperley also isn’t convinced that metallic hydrogen will necessarily turn into a game-changing rocket fuel. He doesn’t think it will remain stable once the pressure upon it is released, the way that a diamond does. Instead, he expects that it will revert to a molecular form that’s stable only at low pressure.  “I think the most likely application,” he says, “is to teach us how to make better superconductors out of hydrogen-containing compounds. Clearly pure metallic hydrogen by itself will be at too high a pressure to be useful.”

NOW THAT’S INTERESTING

According to the 2005 scientific textbook “Structure-Property Relations in Nonferrous Metals,” while metallic hydrogen would be an exotic material on Earth, it’s likely to be abundant within the interiors of Jupiter-sized gas planets in other solar systems; the authors write that it might even be “the most common metal in the universe as a whole.”

Physicists address loophole in tests of Bell’s inequality using 600-year-old starlight

Physicists address loophole in tests of Bell’s inequality using 600-year-old starlight

Physicists from MIT, the University of Vienna, and elsewhere have presented a strong demonstration of quantum entanglement even when vulnerability to the freedom-of-choice loophole is significantly restricted. Credit: Christine Daniloff/MIT

Quantum entanglement may appear to be closer to science fiction than anything in our physical reality. But according to the laws of quantum mechanics—a branch of physics that describes the world at the scale of atoms and subatomic particles—quantum entanglement, which Einstein once skeptically viewed as “spooky action at a distance,” is, in fact, real.

Imagine two specks of dust at opposite ends of the universe, separated by several billion light years. Quantum theory predicts that, regardless of the vast distance separating them, these two particles can be entangled. That is, any measurement made on one will instantaneously convey information about the outcome of a future measurement on its partner. In that case, the outcomes of measurements on each member of the pair can become highly correlated.

If, instead, the universe behaves as Einstein imagined it should—with particles having their own, definite properties prior to measurement, and with local causes only capable of yielding local effects—then there should be an upper limit to the degree to which measurements on each member of the pair of particles could be correlated. Physicist John Bell quantified that upper limit, now known as “Bell’s inequality,” more than 50 years ago.

In numerous previous experiments, physicists have observed correlations between particles in excess of the limit set by Bell’s inequality, which suggests that they are indeed entangled, just as predicted by . But each such test has been subject to various “loopholes,” scenarios that might account for the observed correlations even if the world were not governed by .

Now, physicists from MIT, the University of Vienna, and elsewhere have addressed a loophole in tests of Bell’s inequality, known as the freedom-of-choice loophole, and have presented a strong demonstration of even when the vulnerability to this loophole is significantly restricted.

“The real estate left over for the skeptics of quantum mechanics has shrunk considerably,” says David Kaiser, the Germeshausen Professor of the History of Science and professor of physics at MIT. “We haven’t gotten rid of it, but we’ve shrunk it down by 16 orders of magnitude.”

A research team including Kaiser; Alan Guth, the Victor F. Weisskopf Professor of Physics at MIT; Andrew Friedman, an MIT research associate; and colleagues from
the University of Vienna and elsewhere has published its results today in the journal Physical Review Letters.

Closing the door on quantum alternatives

The freedom-of-choice loophole refers to the idea that experimenters have total freedom in choosing their experimental setup, from the types of particles to entangle, to the measurements they choose to make on those particles. But what if there were some other factors or hidden variables correlated with the experimental setup, making the results appear to be quantumly entangled, when in fact they were the result of some nonquantum mechanism?

Physicists have attempted to address this loophole with extremely controlled experiments, in which they produce a pair of entangled photons from a single source, then send the photons to two different detectors and measure properties of each photon to determine their degree of correlation, or entanglement. To rule out the possibility that hidden variables may have influenced the results, researchers have used random number generators at each detector to decide what property of each photon to measure, in the split second between when the photon leaves the source and arrives at the detector.

But there is a chance, however slight, that hidden variables, or nonquantum influences, may affect a random number generator before it relays its split-second decision to the photon detector.

“At the heart of quantum entanglement is the high degree of correlations in the outcomes of measurements on these pairs [of particles],” Kaiser says. “But what if a skeptic or critic insisted these correlations weren’t due to these particles acting in a fully quantum mechanical way? We want to address whether there is any other way that those correlations could have snuck in without our having noticed.”

“Stars aligned”

In 2014, Kaiser, Friedman, and their colleague Jason Gallicchio (now a professor at Harvey Mudd College) proposed an experiment to use ancient photons from astronomical sources such as stars or quasars as “cosmic setting generators,” rather than on Earth, to determine the measurements to be made on each entangled photon. Such cosmic light would be arriving at Earth from objects that are very far away—anywhere from dozens to billions of light years away. Thus, if some hidden variables were to interfere with the randomness of the choice of measurements, they would have had to have set those changes in motion before the time the light left the cosmic source, long before the experiment on Earth was conducted.

In this new paper, the researchers have demonstrated their idea experimentally for the first time. The team, including Professor Anton Zeilinger and his group at the

University of Vienna and the Austrian Academy of Sciences, set up a source to produce highly entangled pairs of photons on the roof of a university laboratory in Vienna. In each experimental run, they shot the entangled photons out in opposite directions, toward detectors located in buildings several city blocks away—the Austrian National Bank and a second university building.

The researchers also set up telescopes at both detector sites and trained them on stars, the closest of which is about 600 light years away, which they had previously determined would send sufficient photons, or starlight, in their direction.

“On those nights, the stars aligned,” Friedman says. “And with bright stars like these, the number of photons coming in can be like a firehose. So we have these very fast detectors that can register detections of cosmic photons on subnanosecond timescales.”

“Out of whack” with Einstein

In the few microseconds before an entangled photon arrived at a detector, the researchers used each telescope to rapidly measure a property of an incoming stellar photon—in this case, whether its wavelength was redder or bluer than a particular reference wavelength. They then used this random property of the stellar photon, generated 600 years ago by its star, to determine what property of the incoming entangled photons to measure. In this case, red stellar photons signaled a detector to measure an entangled photon’s polarization in a particular direction. A blue stellar photon would set the device to measure the polarization of the entangled particle along a different direction.

The team conducted two experiments, with each experimental run lasting only three minutes. In each case, the researchers measured about 100,000 pairs of . They found that the polarization measurements of the photon pairs were highly correlated, well in excess of the bound set by Bell’s inequality, in a way that is most easily explained by quantum mechanics.

“We find answers consistent with quantum mechanics to an enormously strong degree, and enormously out of whack with an Einstein-like prediction,” Kaiser says.

The results represent improvements by 16 orders of magnitude over previous efforts to address the freedom-of-choice loophole.

“All previous experiments could have been subject to this weird loophole to account for the results microseconds before each experiment, versus our 600 years,” Kaiser says. “So it’s a difference of a millionth of a second versus 600 years’ worth of seconds—16 orders of magnitude.”

“This experiment pushes back the latest time at which the conspiracy could have started,” Guth adds. “We’re saying, in order for some crazy mechanism to simulate
quantum mechanics in our experiment, that mechanism had to have been in place 600 years ago to plan for our doing the experiment here today, and to have sent photons of just the right messages to end up reproducing the results of quantum mechanics. So it’s very far-fetched.”

There is also a second, equally far-fetched possibility, says Michael Hall, a senior research fellow at Griffith University in Brisbane, Australia.

“When photons from the distant stars reach the devices that determine the measurement settings, it is possible that these devices act in some way to change the colors of the photons, in a way that is correlated with the laser producing the entanglement,” says Hall, who was not involved in the work. “This would only require a 10-microsecond-old conspiracy between the devices and the laser. However, the idea that photons don’t show their ‘true colors’ when detected would overturn all observational astronomy and basic electromagnetism.”

Explore further: Quantum physics mimics spooky action into the past

More information: Cosmic Bell Test: Measurement Settings from Milky Way Stars. arxiv.org/abs/1611.06985v2

Read more at: https://phys.org/news/2017-02-physicists-loophole-bell-inequality-year-old.html#jCp

Material can turn sunlight, heat and movement into electricity—all at once

sunny

Credit: Marina Shemesh/public domain

Many forms of energy surround you: sunlight, the heat in your room and even your own movements. All that energy—normally wasted—can potentially help power your portable and wearable gadgets, from biometric sensors to smart watches. Now, researchers from the University of Oulu in Finland have found that a mineral with the perovskite crystal structure has the right properties to extract energy from multiple sources at the same time.

Perovskites are a family of minerals, many of which have shown promise for harvesting one or two types of at a time—but not simultaneously. One family member may be good for solar cells, with the right properties for efficiently converting solar energy into electricity. Meanwhile, another is adept at harnessing energy from changes in temperature and pressure, which can arise from motion, making them so-called pyroelectric and piezoelectric materials, respectively.

Sometimes, however, just one type of energy isn’t enough. A given form of energy isn’t always available—maybe it’s cloudy or you’re in a meeting and can’t get up to move around. Other researchers have developed devices that can harness multiple forms of energy, but they require multiple materials, adding bulk to what’s supposed to be a small and portable device.

This week in Applied Physics Letters Yang Bai and his colleagues at the University of Oulu explain their research on a specific type of perovskite called KBNNO, which may be able to harness many forms of energy. Like all perovskites, KBNNO is a ferroelectric material, filled with tiny electric dipoles analogous to tiny compass needles in a magnet.

When like KBNNO undergo changes in temperature, their dipoles misalign, which induces an electric current. Electric charge also accumulates according to the direction the dipoles point. Deforming the material causes certain regions to attract or repel charges, again generating a current.

Previous researchers have studied KBNNO’s photovoltaic and general ferroelectric properties, but they did so at temperatures a couple hundred degrees below freezing, and they didn’t focus on properties related to temperature or pressure. The new study represents the first time anyone has evaluated all of these properties at once above room temperature, Bai said.

The experiments showed that while KBNNO is reasonably good at generating electricity from heat and pressure, it isn’t quite as good as other perovskites. Perhaps the most promising finding, however, is that the researchers can modify the composition of KBNNO to improve its pyroelectric and piezoelectric properties. “It is possible that all these can be tuned to a maximum point,” said Bai, who, with his colleagues, is already exploring such an improved material by preparing KBNNO with sodium.

Within the next year, Bai said, he hopes to build a prototype multi-energy-harvesting device. The fabrication process is straightforward, so commercialization could come in just a few years once researchers identify the best material.

“This will push the development of the Internet of Things and smart cities, where power-consuming sensors and devices can be energy sustainable,” he said.

This kind of material would likely supplement the batteries on your devices, improving energy efficiency and reducing how often you need to recharge. One day, Bai said, multi-energy harvesting may mean you won’t have to plug in your gadgets anymore. Batteries for small devices may even become obsolete.

Explore further: Stability challenge in perovskite solar cell technology

More information: Yang Bai et al, Ferroelectric, pyroelectric, and piezoelectric properties of a photovoltaic perovskite oxide, Applied Physics Letters (2017). DOI: 10.1063/1.4974735

Read more at: https://phys.org/news/2017-02-material-sunlight-movement-electricityall.html#jCp

Measuring time without a clock

Measuring time without a clock

Credit: Ecole Polytechnique Federale de Lausanne

EPFL scientists have been able to measure the ultrashort time delay in electron photoemission without using a clock. The discovery has important implications for fundamental research and cutting-edge technology.

When light shines on certain materials, it causes them to emit . This is called “” and it was discovered by Albert Einstein in 1905, winning him the Nobel Prize. But only in the last few years, with advancements in laser technology, have scientists been able to approach the incredibly short timescales of photoemission. Researchers at EPFL have now determined a delay of one billionth of one billionth of a second in photoemission by measuring the spin of photoemitted electrons without the need of . The discovery is published in Physical Review Letters.

Photoemission

Photoemission has proven to be an important phenomenon, forming a platform for cutting-edge spectroscopy techniques that allow scientists to study the properties of electrons in a solid. One such property is spin, an intrinsic quantum property of particles that makes them look like as if they were rotating around their axis. The degree to which this axis is aligned towards a particular direction is referred to as , which is what gives some materials, like iron, magnetic properties.

Although there has been great progress in using photoemission and spin polarization of photo-emitted electrons, the time scale in which this entire process takes places have not been explored in great detail. The common assumption is that, once light reaches the material, electrons are instantaneously excited and emitted. But more recent studies using advanced laser technology have challenged this, showing that there is actually a time delay on the scale of attoseconds.

Time without a clock

The lab of Hugo Dil at EPFL, with colleagues in Germany, showed that during photoemission, the spin polarization of emitted electrons can be related to the attosecond time delays of photoemission. More importantly, they have shown this without the need for any experimental time resolution or measurement—essentially, without the need for a clock. To do this, the scientists used a type of photoemission spectroscopy (SARPES) to measure the spin of electrons photo-emitted from a crystal of copper.

“With lasers you can directly measure the between different processes, but it is difficult to determine when a process starts – time zero,” says Mauro Fanciulli, a PhD student of Dil’s group and first author on the paper. “But in our experiment we measure time indirectly, so we don’t have that problem – we could access one of the shortest timescales ever measured. The two techniques [spin and lasers], are complementary, and together they can yield a whole new realm of information.”

The information about the timescale of photoemission is included in the wavefunction of the emitted electrons. This is a quantum description of the probability of where any given electron can be found at any given time. By using SAPRES, the scientists were able to measure the spin of the electrons, which in turn allowed them to access their wavefunction properties.

“The work is a proof of principle that can trigger further fundamental and applied research,” says Hugo Dil. “It deals with the fundamental nature of time itself and will help understand the details of the photoemission process, but it can also be used in photoemission spectroscopy on materials of interest.” Some of these materials include graphene and high-temperature superconductors, which Dil and his colleagues will be studying next.

Read more at: https://phys.org/news/2017-02-clock.html#jCp

Never-before-seen topological solitons experimentally realized in liquid crystals

topological soliton

A polarizing optical micrograph of the twistion, a type of topological soliton, observed in chiral nematic liquid crystals. Credit: Ackerman and Smalyukh. Published by the American Physical Society

Read more at: https://phys.org/news/2017-02-never-before-seen-topological-solitons-experimentally-liquid.html#jCp

(Phys.org)—Physicists have discovered that dozens of 3-D knotted structures called “topological solitons,” which have remained experimentally elusive for hundreds of years, can be created and frozen for long periods of time in liquid crystals like those used in electronic displays. Until now, topological solitons have been realized only in a few experiments, and for such a short time that it has been impossible to study them in any detail.

The new results may change all that, as they provide a way to produce a wide diversity of long-lasting topological solitons that can be studied with microscopes and, perhaps one day, play a role in novel optical and electrical applications.

The researchers, Paul J. Ackerman and Ivan I. Smalyukh at the University of Colorado, Boulder, have published a paper on the experimental realization of topological solitons in a recent issue of Physical Review X.

“Our work establishes experimental and numerical approaches for detailed studies of 3-D topological solitons, with the great advantage of enabling a direct comparison between experimental and theoretical results and with a potential impact on many branches of physics and the mathematical field of topology,” Smalyukh told Phys.org. “Our work not only experimentally demonstrates 3-D topological solitons that mathematicians and theoretical physicists envisaged previously, but also reveals a series of solitonic structures that have not been anticipated.”

 

https://phys.org/news/2017-02-never-before-seen-topological-solitons-experimentally-liquid.html

 

Knotted background

Interest in topological solitons dates back to the early 1800s, when the mathematician Carl Friedrich Gauss suggested that the lines of magnetic and electric fields form 3-D knots that might behave like particles. Later, Lord Kelvin and others considered knotted vortices as an early model of the atom, in which the knots’ properties could explain the chemical properties of the different elements.

Currently, many models in physics and cosmology involve topological solitons—for instance, models of condensed matter systems, elementary particles, magnetic monopoles, and magnetic particles called skyrmions that play a role in the emerging field of spintronics.

What exactly are topological solitons? If you take two or more circular rings, link them together to make a chain, then distort the rings by twisting and pulling on them as if they were made of putty, and finally embed the entire structure into a background surface, the result would look like a topological soliton. Describing these objects in more precise detail requires defining them as four-dimensional objects called “three-spheres,” and then converting these four-dimensional objects into three-dimensional objects using a mathematical technique called Hopf mapping. It’s these 3-D objects, called “preimages,” that are the linked rings shown in visual representations.

One of the reasons why topological solitons are so difficult to experimentally realize is that they correspond to a physical system’s lowest energy state in order to be stable. For this reason, they have been demonstrated only as transient structures in liquid crystals. It’s also possible that topological solitons may exist in another medium, chiral ferromagnets, but a lack of experimental imaging techniques prevents researchers from observing them.

topological solitons

An assortment of topological solitons, depicted by computer simulations, illustrations of Hopf maps, and polarizing optical micrographs. Credit: Ackerman and Smalyukh. Published by the American Physical Society

Freezing knots

In the new study, the researchers developed a method to “freeze” topological solitons in a solid film of chiral through a polymerization process involving low levels of ultraviolet light, along with heating and cooling. To enable the experiment to be broadly accessible, the researchers used commercially available liquid crystals, to which they added chiral dopants. Using optical tweezers to generate and manipulate patterns in the pre-frozen liquid crystals, the researchers could also control the types of topological solitons being made.

After the topological solitons are frozen into the liquid crystals, the researchers can study them using an optical microscope—specifically, a three-photon excitation fluorescence polarizing microscope, which produces an optical signal that can be used to construct 3-D images of the solitons.

In the second part of their study, the researchers showed how this data could then be used to make numerical simulations corresponding to the highly complex physical structures. This process is based on analyzing the energetically favorable twisting patterns that minimize the liquid crystals’ elastic free energy. Essentially, this process of converting the experimental structures (preimages) to numerical models is analogous to the mathematical Hopf mapping of 3-D objects (preimages) to four dimensions.

Potential applications

The ability to generate long-lasting topological solitons also opens the doors to potential applications. One idea is to take advantage of the fact that different topological solitons have distinct optical properties, which could be used in optical devices that shift the phase of light, as well as in pixels for optical displays. In addition, if the topological solitons identified here in liquid crystals also exist in solid ferromagnets, the researchers expect that they could potentially revolutionize the field of skyrmionics, in which skyrmions could be used to construct magnetic devices, such as data storage and logic.

topological solitons

Linking diagrams and graphs of some 3D topological solitons. Credit: Ackerman and Smalyukh. Published by the American Physical Society

“The large variety of localized long-term stable topological solitons, combined with the unique electro-optic properties of the host medium, will inevitably lead to technological applications, such as electro-optic devices and bistable information displays,” Ackerman said. “A broad spectrum of new opportunities also emerge on the fundamental side, where our research group will work to establish how different topological solitons can transform one to another and also how the solitons with large Hopf index values can be experimentally realized.”

Overall, one of the biggest advantages of the new method is that it provides a much more comprehensive, detailed analysis of topological soliton preimages than other construction methods. As a result, the new method uncovers small details in the topology that could easily be missed otherwise, such as subtle differences between very similar structures that could have been mistaken to be the same structure. The results show that topological solitons are more complex and diverse than previous evidence could show, and indicate that many more of these structures are still waiting to be discovered.

“An infinitely large number of topological solitons may potentially exist, especially when considering different physical systems,” Smalyukh said.

Explore further: Towards new IT devices with stable and transformable solitons

More information: Paul J. Ackerman and Ivan I. Smalyukh. “Diversity of Knot Solitons in Liquid Crystals Manifested by Linking of Preimages in Torons and Hopfions.” Physical Review X. DOI: 10.1103/PhysRevX.7.011006

Read more at: https://phys.org/news/2017-02-never-before-seen-topological-solitons-experimentally-liquid.html#jCp

Radiation levels in the Fukushima reactor are soaring unexpectedly

The radiation levels inside Japan’s damaged Fukushima Daiichi nuclear reactor No. 2 have soared in recent weeks, reaching a maximum of 530 sieverts per hour, a number experts have called “unimaginable“.

Radiation is now by far the highest it has been since the reactor was struck by a tsunami in March 2011 – and scientists are struggling to explain what’s going on.

The previous maximum radiation level recorded in the reactor was 73 sieverts per hour, a reading taken not long after the meltdown almost six years ago. The levels are now more than seven times that amount.

Exactly what’s causing the levels to creep upwards again is currently stumping the Tokyo Electric Power Company (Tepco). But the good news is that they say the radiation is safely contained within the reactor, so there’s no risk to the greater population.

The latest readings were taken near the entrance of the No. 2 reactor, immediately below the pressure vessel that contains the reactor core.

To get an idea of the radiation levels inside, the team used a remote-operated camera to take photos of the area – the deepest point in the reactor to date – and then analysed the electronic noise in the images to measure radiation levels.

The technique has an error margin of plus or minus 30 percent, which means that it’s not highly accurate. But even at the lowest end of the measurements, the levels would still be 370 sieverts per hour – and could be as high as 690 sieverts per hour.

These unexpectedly high levels are complicating Tepco’s plan to decommission the nuclear reactor. The most recent aim was to have workers find the fuel cells and start dismantling the plant by 2021 – a job that’s predicted to take up to half a century.

But the levels within reactor No. 2, at least, are in no way safe for humans.

The Japanese National Institute of Radiological Sciences told Japan Times that medical professionals have no experience dealing with radiation levels this high – for perspective, a single dose of just 1 sievert of radiation could lead to infertility, hair loss, and sickness.

Four sieverts of radiation exposure in a short period of time would kill 50 percent of people within a month. Ten sieverts would kill a person within three weeks.

Even the remote-operated camera sent in to capture these images is only designed to withstand 1,000 sieverts of radiation, which means it won’t last more than two hours in the No. 2 reactor.

It’s not yet clear exactly what’s causing the high levels either. It’s possible that previous readings were incorrect or not detailed enough, and levels have always been this high. Or maybe something inside the reactor has changed.

The fact that these readings were so high in this particular location suggests that maybe melted reactor fuel escaped the pressure vessel, and is located somewhere nearby.

Adding to that hypothesis is the fact that the images reveal a gaping 1-metre (3.2-foot) hole in the metal grate underneath the pressure vessel – which could indicate that nuclear fuel had melted out of it.

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On Monday, Tepco also saw “black chunks” deposited on the grating directly under the pressure vessel – which could be evidence of melted fuel rods.

If confirmed, this would be a huge deal, because in the six years since the three Fukushima reactors went into meltdown, no one has ever been able to find any trace of the nuclear fuel rods.

Swimming robots were sent into the reactors last year to search for the fuel rods and hopefully remove them, but their wiring was destroyed by the high levels of radiation.

Naturally, Tepco is reluctant to jump to any conclusions on what the black mass in the images could be until they have more information.

“It may have been caused by nuclear fuel that would have melted and made a hole in the vessel, but it is only a hypothesis at this stage,” a Tepco spokesperson told AFP.

“We believe the captured images offer very useful information, but we still need to investigate given that it is very difficult to assume the actual condition inside.”

Given the new readings, Tepco is now putting their plans to further explore reactor No. 2 using remote operated camera on hold, seeing as the device will most likely be destroyed by the intense conditions.

But they will send a robot into reactor No. 1 in March to try to get a better idea about the internal condition of the structure, while they decide what to do next with reactor No. 2.