Scientists have solved a decade-long puzzle about lithium, an essential metal in cellphone and computer batteries. Using extreme pressure experiments and powerful supercomputing, the international team has unraveled the mystery of a fundamental property of lithium; its atoms are arranged in a simple structure, and may be the first direct evidence of a quantum solid behavior in a metal.

Until now, all previous experiments have indicated that lithium’s atoms had a complex arrangement. The idea baffled theoretical physicists. With only three electrons, lithium is the lightest, simplest metal on the periodic table and should have a simple structure to match.

The new study combined theory and experimentation to discover the true structure of lithium at cold temperatures, in its lowest energy state.

Scientists suggest that rapid cooling led lithium atoms to arrange themselves in complex structure and resulted in misinterpretation of the previous experimental results. To avoid this, Shanti Deemyad, associate professor at the University of Utah who led the experimental aspect of the study, applied extreme pressure to the lithium before cooling down the samples.

Deemyad’s research group prepared the lithium samples in tiny pressure cells at the U. The group then traveled to Argonne National Laboratory to apply pressure up to 10,000 times the Earth’s atmosphere by pressing the sample between the tip of two diamonds. They then cooled and depressurized the samples examined the structures at low pressure and temperature using X-ray beams.

The researchers looked at two isotopes of lithium — the lighter lithium 6 and heavier lithium 7. They found that the lighter isotope behaves differently in its transitions to lower energy structures under certain thermodynamic paths than the heavier isotope, a behavior previously only seen in helium. The difference means that depending on the weight of the nuclei, there are different ways to get to the lower energy states. This is a quantum solid characteristic.

Graeme Ackland, professor from the University of Edinburgh, led the theoretical aspect of the study by running the most sophisticated calculations of lithium’s structure to date, using advanced quantum mechanics on the ARCHER supercomputer. Both experimentation and theoretical parts of the study found that lithium’s lowest energy structure is not complex or disordered, as previous results had suggested. Instead, its atoms are arranged simply, like oranges in a box.

The study, from the Universities of Edinburgh and Utah, was published in Science.

Corresponding author Deemyad of the University of Utah Department of Physics & Astronomy, said: “Our experiments revealed that lithium is the first metallic element with quantum lattice structure behavior at moderate pressures. This will open up new possibilities for rich physics.”

Co-author Miguel Martinez-Canales of the University of Edinburgh School of Physics and Astronomy, said: “Our calculations needed an accuracy of one in 10 million, and would have taken over 40 years on a normal computer.”

Lead theoretical author Graeme Ackland of the University of Edinburgh School of Physics and Astronomy, said: “We were able to form a true picture of cold lithium by making it using high pressures. Rather than forming a complex structure, it has the simplest arrangement that there can be in nature.”

Read the full press release on the UNews website

 

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U-led Study Discovers a “Miracle Material” for Field of Spintronics

A University of Utah-led team has discovered that a class of “miracle materials” called organic-inorganic hybrid perovskites could be a game changer for future spintronic devices.

Spintronics uses the direction of the electron spin - either up or down - to carry information in ones and zeros. A spintronic device can process exponentially more data than traditional electronics that use the ebb and flow of electrical current to generate digital instructions. But physicists have struggled to make spintronic devices a reality.

The new study, published online today in Nature Physics, is the first to show that organic-inorganic hybrid perovskites are a promising material class for spintronics. The researchers discovered that the perovskites possess two contradictory properties necessary to make spintronic devices work — the electrons’ spin can be easily controlled, and can also maintain the spin direction long enough to transport information, a property known as spin lifetime.

“It’s a device that people always wanted to make, but there are big challenges in finding a material that can be manipulated and, at the same time, have a long spin lifetime,” says Sarah Li, assistant professor in the Department of Physics & Astronomy at the U and lead author of the study. “But for this material, it's the property of the material itself that satisfies both.”

The Miracle Material

Organic-inorganic hybrid perovskites is already famous in scientific circles for being amazingly efficient at converting sunlight into electricity.

“It’s unbelievable. A miracle material,” says Z. Valy Vardeny, distinguished professor in the Department of Physics & Astronomy and co-author of the study, whose lab studies perovskite solar cells. “In just a few years, solar cells based on this material are at 22% efficiency. And now it has this spin lifetime property. It’s fantastic.”

The material’s chemical composition is an unlikely candidate for spintronics, however. The hybrid perovskite inorganic frame is made of heavy elements. The heavier the atom, the easier it is to manipulate the electron spin. That’s good for spintronics. But other forces also influence the spin. When the atoms are heavy, you assume the spin lifetime is short, explains Li.

“Most people in the field would not think that this material has a long spin lifetime. It’s surprising to us, too,” says Li. “We haven't found out the exact reason yet. But it's likely some intrinsic, magical property of the material itself.”

Spintronics: That Magnetic Moment When…

Cellphones, computers and other electronics have silicon transistors that control the flow of electrical currents like tiny dams. As devices get more compact, transistors must handle the electrical current in smaller and smaller areas.

“The silicon technology, based only on the electron charge, is reaching its size-limit,” says Li, “The size of the wire is already small. If gets any smaller, it’s not going to work in a classical way that you think of.”

“People were thinking, ‘How do we increase the amount of information in such a small area?’” adds Vardeny. “What do we do to overcome this limit?”

“Spintronics,” answers physics.

Spintronics uses the spin of the electron itself to carry information. Electrons are basically tiny magnets orbiting the nucleus of an element. Just like the Earth has its own orientation relative to the sun, electrons have their own spin orientation relative to the nucleus that can be aligned in two directions: “Up,” which represents a one, and “down,” which represents a zero. Physicists relate the electron’s “magnetic moment” to its spin.

By adding spin to traditional electronics, you can process exponentially more information than using them classically based on less or more charge.

“With spintronics, not only have you enormously more information, but you’re not limited by the size of the transistor. The limit in size will be the size of the magnetic moment that you can detect, which is much smaller than the size of the transistor nowadays,” says Vardeny.

The Experiment to Tune Electron Spin

Tuning an electron spin is like tuning a guitar, but with a laser and a lot of mirrors.

First, the researchers formed a thin film from the hybrid perovskite methyl-ammonium lead iodine (CH₃NH₃PbI₃) and placed it in front of an ultrafast laser that shoots very short light pulses 80 million times a second. The researchers are the first to use light to set the electron’s spin orientation and observe the spin precession in this material.

They split the laser into two beams; the first one hit the film to set the electron spin in the desired direction. The second beam bends through a series of mirrors like a pinball machine before hitting the perovskite film at increasing time intervals to measure how long the electron held the spin in the prepared direction.

They found that the perovskite has a surprisingly long spin lifetime — up to nanosecond. The spin flips many times during one nanosecond, which means a lot information can be easily stored and manipulated during that time.

Once they determined the long spin lifetime, the researchers tested how well they could manipulate the spin with a magnetic field.

“The spin is like the compass. The compass spins in this magnetic field perpendicular to that compass, and eventually it will stop spinning,” says Li. “Say you set the spin to ‘up,’ and you call that ‘one.’ When you expose it to the magnetic field, the spin changes direction. If it rotated 180 degrees, it changes from one to zero. If it rotated 360 degrees, it goes from one to one.”

They found that they could rotate the spin more than 10 turns by exposing the electron to different strengths of magnetic field.

The potential for this material is enormous, says Vardeny. It could process data faster and increase random-access memory.

“I’m telling you, it’s a miracle material,” says Vardeny.

Li and Vardeny conducted the research with first authors Patrick Odenthal and William Talmadge, Nathan Gundlach, Chuang Zhang and Dali Sun from the Department of Physics & Astronomy at the University of Utah; Zhi-Gang Yu of the ISP/ Applied Sciences Laboratory at Washington State University; and Ruizhi Wang, who is now at the School of Electronic and Optical Engineering at Nanjing University of Science and Technology.

The work was supported by a start-up grant from the University of Utah and the United States Department of Energy Office of Science grant DES0014579. The National Science Foundation Material Science and Engineering Center at the University of Utah (DMR-1121252) supported perovskite growth and facilities.

Read the full press release on the UNews website

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Astronomers with the international, multi-institutional Sloan Digital Sky Survey have used the world's largest sample of quasars to map a previously uncharted region of the universe. Quasars are brilliant, distant points of light powered by supermassive black holes at their centers. As matter and energy fall into a quasar’s black hole, they heat up to incredible temperatures and glow brighter than anything else in the universe. That luminescence is captured by a 2.5 meter-diameter telescope on a mountaintop in New Mexico here on Earth.

Kyle Dawson, associate professor of physics and astronomy at the University of Utah, is the lead U.S. scientist on this cosmology project. He led the team to prepare and acquire the data for more than 147,000 quasars using the telescope at the Apache Point Observatory in Sunspot, New Mexico. His group oversaw the survey planning, observations, and software that turned the photons of light emitted by the quasars into data that can be understood by the rest of the team.

“Quasars are like bright, little lighthouses spread around the galaxy,” says Dawson. “We use them like beacons to see where matter is distributed in the universe.”

From the Sloan Digital Sky Survey (SDSS) website.

"Astronomers with the Sloan Digital Sky Survey (SDSS) have created the first map of the large-scale structure of the Universe based entirely on the positions of quasars. Quasars are the incredibly bright and distant points of light powered by supermassive black holes.

“Because quasars are so bright, we can see them all the way across the Universe,” said Ashley Ross of the Ohio State University, the co-leader of the study. “That makes them the ideal objects to use to make the biggest map yet.”

The amazing brightness of quasars is due to the supermassive black holes found at their centers. As matter and energy fall into a quasar’s black hole, they heat up to incredible temperatures and begin to glow. It is this bright glow that is detected by a dedicated 2.5-meter telescope here on Earth.

“These quasars are so far away that their light left them when the Universe was between three and seven billion years old, long before the Earth even existed,” said Gongbo Zhao from the National Astronomical Observatories of Chinese Academy of Sciences, the study’s other co-leader.

To make their map, scientists used the Sloan Foundation Telescope to observe an unprecedented number of quasars. During the first two years of the SDSS’s Extended Baryon Oscillation Spectroscopic Survey (eBOSS), astronomers measured accurate three-dimensional positions for more than 147,000 quasars.

The telescope’s observations gave the team the quasars’ distances, which they used to create a three-dimensional map of where the quasars are. But to use the map to understand the expansion history of the Universe, they had to go a step further, using a clever technique involving studying “baryon acoustic oscillations” (BAOs). BAOs are the present-day imprint of sound waves which travelled through the early Universe, when it was much hotter and denser than the Universe we see today. But when the Universe was 380,000 years old, conditions changed suddenly and the sound waves became “frozen” in place. These frozen waves are left imprinted in the three-dimensional structure of the Universe we see today.

The good news about these frozen waves – the original baryon acoustic oscillations – is that the process that produced them is simple. Thus, we have a good understanding of what BAOs must have looked like at that ancient time. When we look at the three-dimensional structure of the Universe today, it contains these same BAOs grown out to a huge scale by the expansion of the Universe. The observed size of the BAO can be used as a “standard ruler” to measure distances. Just as by using the apparent angle of a meter stick viewed from the other side of a football field, you can estimate the length of the field. “You have meters for small units of length, kilometres or miles for distances between cities, and we have the BAO scale for distances between galaxies and quasars in cosmology,” explained Pauline Zarrouk, a PhD student at the Irfu/CEA, University Paris-Saclay, who measured the projected BAO scale.

Astronomers from the SDSS have previously used the BAO technique on nearby galaxies and then on intergalactic gas distributions to push this analysis farther and farther back in time. The current results cover a range of times where they have never been observed before, measuring the conditions when the Universe more than two billion years before the Earth formed.

The results of the new study confirm the standard model of cosmology that researchers have built over the last twenty years. In this standard model, the Universe follows the predictions of Einstein’s General Theory of Relativity — but includes components whose effects we can measure, but whose causes we do not understand. Along with the ordinary matter that makes up stars and galaxies, the Universe includes dark matter – invisible yet still affected by gravity – and a mysterious component called “Dark Energy.” Dark Energy is the dominant component at the present time, and it has special properties that cause the expansion of the Universe to speed up.

“Our results are consistent with Einstein’s theory of General Relativity” said Hector Gil-Marin, a researcher from the Laboratoire de Physique Nucléaire et de hautes Énergies in Paris who undertook key parts of the analysis. “We now have BAO measurements covering a range of cosmological distances, and they all point to the same thing: the simple model matches the observations very well.”

Even though we understand how gravity works, we still do not understand everything – there is still the question of what exactly dark energy is. “We would like to understand Dark Energy further,” said Will Percival from the University of Portsmouth, who is the eBOSS survey scientist. “Surveys like eBOSS are helping us to build up our understanding of how dark energy fits into the story of the Universe.”

The eBOSS experiment is still continuing, using the Sloan Telescope at Apache Point Observatory in New Mexico, USA. As astronomers with eBOSS observe more quasars and nearby galaxies, the size of their map will continue to increase. After eBOSS is complete, a new generation of sky surveys will begin, including the Dark Energy Spectroscopic Instrument (DESI) and the European Space Agency Euclid satellite mission. These will increase the fidelity of the maps by a factor of ten compared with eBOSS, revealing the Universe and Dark Energy in unprecedented detail."

Kyle Dawson's post-doctoral researchers whom also worked on this project are:
Julian Bautista: oversees development, maintenance, and operations of the software to process all of the spectra from eBOSS
Vivek Mariappan: coordinates all preparation, operations and observing planning for eBOSS"

Read the full press release on the SDSS website

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New Supernova is Bright Enough to Spot from Earth

On May 13, 2017, "Phun With Physics" Outreacher and NASA solar system ambassador to Utah, Patrick Wiggins spotted something unusual in the sky. He was looking at the spiral galaxy NGC 6946 (the "Fireworks Galaxy") in Cygnus, over 22 million light-years away from his telescope and home near Erda, UT. He noticed a bright spot that he hadn't seen before. By comparing what he what he was seeing with earlier photographs taken of the same galaxy, he realized he was witnessing a star explode.

Named "SN 2017aew", Patrick Wiggins' discovery was confirmed on May 14th by two astronomers: Dr. Subo Dong from the Kavli Institute for Astronomy and Astrophysics (KIAA) at Peking University, and Dr. Krzysztof Z. Stanek from The Ohio State University, both experts in supernovae.

When a star goes supernova, it is one of the largest, and most impressive astronomical events in space. Situated between a nova and a hypernova in terms of total energy, a supernova occurs when a star's core changes in some manner. This can be due to either a white dwarf gaining too much mass from another star orbiting around the same point in a binary star system until the white dwarf's core is so dense that it collapses due to the overwhelming gravitational force (known as a Type I Supernova), or a massive star (many, many times larger than our own sun) reaches the end of its life and runs out of nuclear fuel. The star's core collapses from its own staggering gravitational forces and explodes (a Type II Supernova). In both cases, these supernovae are astoundingly bright for a time - bright enough to be seen by amateur and professional astronomers alike - until they expend their energy and their bright light begins to fade over the next few months.

This most recent discovery, SN 2017aew, has been confirmed to be a Type II supernova.

This is the third supernova discovery for Patrick Wiggins. He also discovered "SN 2015Q" in the NGC 3888 galaxy in Ursa Major in 2015. In 2014, supernova "SN2014G" was discovered independently by both Koichi Itagaki in Japan, and Patrick Wiggins.

In addition, Patrick Wiggins has discovered a whole host of astronomical events in space, including an asteroid he discovered in 2008, which the International Astronomical Union named "Univofutah", at Patrick's request, to honor the University of Utah. Wiggins' work has earned him many accolades, including the prestigious Distinguished Public Service Medal, NASA's highest civilian honor.

This story is still developing and will be updated as new information becomes available. Stay tuned.

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