From SLAC: “Scientists Use Machine Learning to Speed Discovery of Metallic Glass”

SLAC Lab

April 13, 2018
Glennda Chui

Fang Ren, who developed algorithms to analyze data on the fly while a postdoctoral scholar at SLAC, at a Stanford Synchrotron Radiation Lightsource beamline where the system has been put to use. (Dawn Harmer/SLAC National Accelerator Laboratory)

SLAC and its collaborators are transforming the way new materials are discovered. In a new report, they combine artificial intelligence and accelerated experiments to discover potential alternatives to steel in a fraction of the time.

Blend two or three metals together and you get an alloy that usually looks and acts like a metal, with its atoms arranged in rigid geometric patterns.

But once in a while, under just the right conditions, you get something entirely new: a futuristic alloy called metallic glass that’s amorphous, with its atoms arranged every which way, much like the atoms of the glass in a window. Its glassy nature makes it stronger and lighter than today’s best steel, plus it stands up better to corrosion and wear.

Even though metallic glass shows a lot of promise as a protective coating and alternative to steel, only a few thousand of the millions of possible combinations of ingredients have been evaluated over the past 50 years, and only a handful developed to the point that they may become useful.

Now a group led by scientists at the Department of Energy’s SLAC National Accelerator Laboratory, the National Institute of Standards and Technology (NIST) and Northwestern University has reported a shortcut for discovering and improving metallic glass – and, by extension, other elusive materials – at a fraction of the time and cost.

The research group took advantage of a system at SLAC’s Stanford Synchrotron Radiation Lightsource (SSRL) that combines machine learning – a form of artificial intelligence where computer algorithms glean knowledge from enormous amounts of data – with experiments that quickly make and screen hundreds of sample materials at a time.

SLAC/SSRL

This allowed the team to discover three new blends of ingredients that form metallic glass, and to do this 200 times faster than it could be done before, they reported today in Science Advances.

(Yvonne Tang/SLAC National Accelerator Laboratory)

“It typically takes a decade or two to get a material from discovery to commercial use,” said Northwestern Professor Chris Wolverton, an early pioneer in using computation and AI to predict new materials and a co-author of the paper. “This is a big step in trying to squeeze that time down. You could start out with nothing more than a list of properties you want in a material and, using AI, quickly narrow the huge field of potential materials to a few good candidates.”

The ultimate goal, he said, is to get to the point where a scientist could scan hundreds of sample materials, get almost immediate feedback from machine learning models and have another set of samples ready to test the next day – or even within the hour.

Over the past half century, scientists have investigated about 6,000 combinations of ingredients that form metallic glass, added paper co-author Apurva Mehta, a staff scientist at SSRL: “We were able to make and screen 20,000 in a single year.”

Just Getting Started

While other groups have used machine learning to come up with predictions about where different kinds of metallic glass can be found, Mehta said, “The unique thing we have done is to rapidly verify our predictions with experimental measurements and then repeatedly cycle the results back into the next round of machine learning and experiments.”

There’s plenty of room to make the process even speedier, he added, and eventually automate it to take people out of the loop altogether so scientists can concentrate on other aspects of their work that require human intuition and creativity. “This will have an impact not just on synchrotron users, but on the whole materials science and chemistry community,” Mehta said.

The team said the method will be useful in all kinds of experiments, especially in searches for materials like metallic glass and catalysts whose performance is strongly influenced by the way they’re manufactured, and those where scientists don’t have theories to guide their search. With machine learning, no previous understanding is needed. The algorithms make connections and draw conclusions on their own, and this can steer research in unexpected directions.

“One of the more exciting aspects of this is that we can make predictions so quickly and turn experiments around so rapidly that we can afford to investigate materials that don’t follow our normal rules of thumb about whether a material will form a glass or not,” said paper co-author Jason Hattrick-Simpers, a materials research engineer at NIST. “AI is going to shift the landscape of how materials science is done, and this is the first step.”

Strength in Numbers

The paper is the first scientific result associated with a DOE-funded pilot project where SLAC is working with a Silicon Valley AI company, Citrine Informatics, to transform the way new materials are discovered and make the tools for doing that available to scientists everywhere.

Founded by former graduate students from Northwestern and Stanford University, Citrine has created a materials science data platform where data that had been locked away in published papers, spreadsheets and lab notebooks is stored in a consistent format so it can be analyzed with AI specifically designed for materials.

“We want to take materials and chemical data and use them effectively to design new materials and optimize manufacturing,” said Greg Mulholland, founder and CEO of the company. “This is the power of artificial intelligence: As scientists generate more data, it learns alongside them, bringing hidden trends to the surface and allowing scientists to identify high-performance materials much faster and more effectively than relying on traditional, purely human-driven materials development.”

Until recently, thinking up, making and assessing new materials was painfully slow. For instance, the authors of the metallic glass paper calculated that even if you could cook up and examine five potential types of metallic glass a day, every day of the year, it would take more than a thousand years to plow through every possible combination of metals. When they do discover a metallic glass, researchers struggle to overcome problems that hold these materials back. Some have toxic or expensive ingredients, and all of them share glass’s brittle, shatter-prone nature.

Over the past decade, scientists at SSRL and elsewhere have developed ways to automate experiments so they can create and study more novel materials in less time. Today, some SSRL users can get a preliminary analysis of their data almost as soon as it comes out with AI software developed by SSRL in conjunction with Citrine and the CAMERA project at DOE’s Lawrence Berkeley National Laboratory.

“With these automated systems we can analyze more than 2,000 samples per day,” said Fang Ren, the paper’s lead author, who developed algorithms to analyze data on the fly and coordinated their integration into the system while a postdoctoral scholar at SLAC.

Experimenting with Data

In the metallic glass study, the research team investigated thousands of alloys that each contain three cheap, nontoxic metals.

They started with a trove of materials data dating back more than 50 years, including the results of 6,000 experiments that searched for metallic glass. The team combed through the data with advanced machine learning algorithms developed by Wolverton and graduate student Logan Ward at Northwestern.

Based on what the algorithms learned in this first round, the scientists crafted two sets of sample alloys using two different methods, allowing them to test how manufacturing methods affect whether an alloy morphs into a glass.

Both sets of alloys were scanned by an SSRL X-ray beam, the data fed into the Citrine database, and new machine learning results generated, which were used to prepare new samples that underwent another round of scanning and machine learning.

By the experiment’s third and final round, Mehta said, the group’s success rate for finding metallic glass had increased from one out of 300 or 400 samples tested to one out of two or three samples tested. The metallic glass samples they identified represented three different combinations of ingredients, two of which had never been used to make metallic glass before.

See the full article here .

Please help promote STEM in your local schools.

Stem Education Coalition

SLAC is a multi-program laboratory exploring frontier questions in photon science, astrophysics, particle physics and accelerator research. Located in Menlo Park, California, SLAC is operated by Stanford University for the DOE’s Office of Science.

Advertisements

From Harvard via Science Alert: “Scientists Just Achieved The World’s Most Precise Chemical Reaction”

Harvard University

Science Alert

13 APR 2018
MIKE MCRAE

(johnason/istock)

Scientists have just performed the world’s most precisely controlled chemical reaction, sticking together just two atoms from elements that wouldn’t normally form a molecule.

The two elements – sodium and caesium – produced an interesting alloy-like molecule. On top of that, this method of creation could set the way of making just the kind of materials we might need in future technology.

A team of Harvard University scientists used laser ‘tweezers’ to manipulate individual atoms of the two alkali metals into close proximity, and provided a photon to help them bond into a single molecule.

Chemical reactions are usually hit-and-miss affairs, where vast numbers of atoms are thrown together under the right conditions, and probability does the rest.

This ‘stochastic’ method of chemical reactions is all well and good if the combination of elements are a decent match. But when scientists want a really exotic pairing, they need to get creative.

Sodium (Na) and caesium (Cs) are both found in the same group on the periodic table – as you may remember from high school chemistry, it means they tend to have similar reactive properties.

Periodic table Sept 2017. Wikipedia

They also don’t tend to bump into each other and easily bond as a molecule.

Which is really a shame – the polarised electrical properties of a molecule of NaCs would make it super useful for storing quantum ‘qubit’ states of superposition that can also interact easily with other components.

This all-in-one combination of qubit storage plus interaction is something desperately needed in future technology.

“The direction of quantum information processing is one of the things we’re excited about,” says lead researcher and chemist Kang-Kuen Ni.

Improbable doesn’t mean impossible, though: if these two atoms happen to be close enough with the right energy, a connection can form.

To achieve this perfect mix of energy and timing, the researchers held single atoms in overlapping magneto-optical traps and pelted them with photons to cool them down to a fraction of a degree above absolute zero.

Meanwhile, they used a pair of lasers tuned to create an electrical effect, causing each atom to move towards each laser’s focus, as if they were pulled into two sci-fi tractor beams.

Nearby, the two atoms can collide easily. This still doesn’t necessarily guarantee they’ll bond, given the need to conserve the right momentum and energy levels.

It’s a tricky juggle of conditions, one the researchers managed using the right laser pulses.

The end result is a brief flicker of a bond between two atoms in the same quantum state, providing the researchers with details on what’s happening on an extremely fine level.

Ni says the next step would be to create longer lasting molecules by combining them while in a ground state, rather than an excited one.

“I think that a lot of scientists will follow, now that we have shown what is possible,” says Ni.

The ultimate goal would be to tailor the creation of far more complex molecules, making use not only of their classical shapes but creating tiny quantum components for the next generation of computing.

And for this kind of construction, nothing can be left to sheer chance.

“The experimental demonstration represents for the first time that a chemical reaction process is deterministically controlled,” Jun Ye of the US National Institute of Standards and Technology told David Bradley from Chemistryworld.

Though Ye wasn’t part of the study, he expressed excitement over the results.

“Control of molecular interactions, including reaction, at the most fundamental level has been a long-standing goal in physical science.”

This research was published in Science.

See the full article here .

Please help promote STEM in your local schools.

Stem Education Coalition

Harvard is the oldest institution of higher education in the United States, established in 1636 by vote of the Great and General Court of the Massachusetts Bay Colony. It was named after the College’s first benefactor, the young minister John Harvard of Charlestown, who upon his death in 1638 left his library and half his estate to the institution. A statue of John Harvard stands today in front of University Hall in Harvard Yard, and is perhaps the University’s best known landmark.

Harvard University has 12 degree-granting Schools in addition to the Radcliffe Institute for Advanced Study. The University has grown from nine students with a single master to an enrollment of more than 20,000 degree candidates including undergraduate, graduate, and professional students. There are more than 360,000 living alumni in the U.S. and over 190 other countries.

From University of Chicago: “Scientists confirm water trapped inside diamonds deep below Earth’s surface”

University of Chicago

March 30, 2018
Karen Mellen

Researchers working at Argonne National Laboratory have identified a form of water trapped within diamonds that crystallized deep in the Earth’s mantle. (Pictured: Rough diamond in kimberlite.) Copyright Getty Images.

Water occurs naturally as far as at least 250 miles below the Earth’s surface, according to a study published in Science last week by researchers from the University of Chicago and others. The discovery, which relies on extremely bright X-ray beams from the Advanced Photon Source at Argonne National Laboratory, could change our understanding of how water circulates deep in the Earth’s mantle and how heat escapes from the lower regions of our planet.

ANL/APS

The researchers identified a form of water known as Ice-VII, which was trapped within diamonds that crystallized deep in the Earth’s mantle. This is the first time Ice-VII has been discovered in a natural sample, making the compound a new mineral accepted by the International Mineralogical Association.

The study is the latest in a long line of research projects at the Advanced Photon Source, a massive X-ray facility used by thousands of researchers every year, which have shed light on the composition and makeup of the deep Earth. Humans cannot explore these regions directly, so the Advanced Photon Source lets them use high-powered X-ray beams to analyze inclusions in diamonds formed in the deep Earth.

UChicago researchers involved in the work at Argonne’s Advanced Photon Source included (from left): Vitali Prakapenka, Tony Lanzirotti, Matt Newville, Eran Greenberg and Dongzhou Zhang. (Photo by Rick Fenner / Argonne National Laboratory).

“We are interested in those inclusions because they tell us about the chemical composition and conditions in the deep Earth when the diamond was formed,” said Antonio Lanzirotti, a UChicago research associate professor and co-author on the study.

In this case, researchers analyzed rough, uncut diamonds mined from regions in China and Africa. Using an optical microscope, mineralogists first identified inclusions, or impurities, which must have formed when the diamond crystallized. But to positively identify the composition of these inclusions, mineralogists needed a stronger instrument: the University of Chicago’s GeoSoilEnviroCARS’s beam lines at the Advanced Photon Source.

Thanks to the very high brightness of the X-rays, which are a billion times more intense than typical X-ray machines, scientists can determine the molecular or atomic makeup of specimens that are only micrometers across. When the beam of X-rays hits the molecules of the specimen, they scatter into unique patterns that reveal their molecular makeup.

What the team identified was surprising: water, in the form of ice.

The composition of the water is the same as the water that we drink and use every day, but in a cubic crystalline form—the result of the extremely high pressure of the diamond.

This form of water, Ice-VII, was created in the lab decades ago, but this study was the first to confirm that it also forms naturally. Because of the pressure required for diamonds to form, the scientists know that these specimens formed between 410 and 660 kilometers (250 to 410 miles) below the Earth’s surface.

The researchers said the significance of the study is profound because it shows that flowing water is present much deeper below the Earth’s surface than originally thought. Going forward, the results raise a number of important questions about how water is recycled in the Earth and how heat is circulated. Oliver Tschauner, the lead author on the study and a mineralogist at University of Nevada in Las Vegas, said the discovery can help scientists create new, more accurate models of what’s going on inside the Earth, specifically how and where heat is generated under the Earth’s crust. This may help scientists better understand one of the driving mechanisms for plate tectonics.

___________________________________________________________
“[T]hanks to the amazing technical capabilities of the Advanced Photon Source, this team of researchers was able to pinpoint and study the exact area on the diamonds that trapped the water”
Stephen Streiffer, associate laboratory director for photon sciences
___________________________________________________________

“This wasn’t easy to find,” said Vitali Prakapenka, a UChicago research professor and a co-author of the study. “People have been searching for this kind of inclusion for a long time.”

For now, the team is wondering whether the mineral Ice-VII will be renamed, now that it is officially a mineral. This is not the first mineral to be identified thanks to research done at the Advanced Photon Source GSECARS beamlines: Bridgmanite, the Earth’s most abundant mineral and a high-density form of magnesium iron silicate, was researched extensively there before it was named. Tschauner was a lead author on that study, too.

“In this study, thanks to the amazing technical capabilities of the Advanced Photon Source, this team of researchers was able to pinpoint and study the exact area on the diamonds that trapped the water,” said Stephen Streiffer, Argonne associate laboratory director for photon sciences and director of the Advanced Photon Source. “That area was just a few microns wide. To put that in context, a human hair is about 75 microns wide.

“This research, enabled by partners from the University of Chicago and the University of Nevada, Las Vegas, among other institutions, is just the latest example of how the APS is a vital tool for researchers across scientific disciplines,” he said.

Other GSECARS co-authors are Eran Greenberg, Dongzhou Zhang and Matt Newville.

In addition to the University of Chicago and UNLV, other institutions cited in the study include the California Institute of Technology, China University of Geosciences, the University of Hawaii at Manoa and the Royal Ontario Museum, Toronto. Data also was collected at Carnegie Institute of Washington’s High Pressure Collaborative Access Team at the Advanced Photon Source and the Advanced Light Source at Lawrence Berkeley National Lab.

LBNL/ALS

LBNL Advanced Light Source storage ring

See the full article here .

Please help promote STEM in your local schools.

Stem Education Coalition

An intellectual destination

One of the world’s premier academic and research institutions, the University of Chicago has driven new ways of thinking since our 1890 founding. Today, UChicago is an intellectual destination that draws inspired scholars to our Hyde Park and international campuses, keeping UChicago at the nexus of ideas that challenge and change the world.

From Rosetta@home via Bloomberg View: “Protein Engineering May Be the Future of Science”

Rosetta@home

Bloomberg View

March 27, 2018
Faye Flam

Some scientists think designing new proteins could become as significant as tweaking DNA.

Let’s build a better sperm whale. Photograph: SSPL/Getty Images

Scientists are increasingly betting their time and effort that the way to control the world is through proteins. Proteins are what makes life animated. They take information encoded in DNA and turn it into intricate three-dimensional structures, many of which act as tiny machines. Proteins work to ferry oxygen through the bloodstream, extract energy from food, fire neurons, and attack invaders. One can think of DNA as working in the service of the proteins, carrying the information on how, when and in what quantities to make them.

Living things make thousands of different proteins, but soon there could be many more, as scientists are starting to learn to design new ones from scratch with specific purposes in mind. Some are looking to design new proteins for drugs and vaccines, while others are seeking cleaner catalysts for the chemical industry and new materials.

David Baker, director for the Institute for Protein Design at the University of Washington, compares protein design to the advent of custom tool-making. At some point, proto-humans went beyond merely finding uses for pieces of wood, rock or bone, and started designing tools to suit specific needs — from screwdrivers to sports cars.

See the full article here.

Please help promote STEM in your local schools.

Stem Education Coalition

Rosetta@home needs your help to determine the 3-dimensional shapes of proteins in research that may ultimately lead to finding cures for some major human diseases. By running the Rosetta program on your computer while you don’t need it you will help us speed up and extend our research in ways we couldn’t possibly attempt without your help. You will also be helping our efforts at designing new proteins to fight diseases such as HIV, Malaria, Cancer, and Alzheimer’s (See our Disease Related Research for more information). Please join us in our efforts! Rosetta@home is not for profit.

About Rosetta

One of the major goals of Rosetta is to predict the shapes that proteins fold up into in nature. Proteins are linear polymer molecules made up of amino acid monomers and are often refered to as “chains.” Amino acids can be considered as the “links” in a protein “chain”. Here is a simple analogy. When considering a metal chain, it can have many different shapes depending on the forces exerted upon it. For example, if you pull its ends, the chain will extend to a straight line and if you drop it on the floor, it will take on a unique shape. Unlike metal chains that are made of identical links, proteins are made of 20 different amino acids that each have their own unique properties (different shapes, and attractive and repulsive forces, for example), and in combination, the amino acids exert forces on the chain to make it take on a specific shape, which we call a “fold.” The order in which the amino acids are linked determines the protein’s fold. There are many kinds of proteins that vary in the number and order of their amino acids.

To predict the shape that a particular protein adopts in nature, what we are really trying to do is find the fold with the lowest energy. The energy is determined by a number of factors. For example, some amino acids are attracted to each other so when they are close in space, their interaction provides a favorable contribution to the energy. Rosetta’s strategy for finding low energy shapes looks like this:

Start with a fully unfolded chain (like a metal chain with its ends pulled).
Move a part of the chain to create a new shape.
Calculate the energy of the new shape.
Accept or reject the move depending on the change in energy.
Repeat 2 through 4 until every part of the chain has been moved a lot of times.

We call this a trajectory. The end result of a trajectory is a predicted structure. Rosetta keeps track of the lowest energy shape found in each trajectory. Each trajectory is unique, because the attempted moves are determined by a random number. They do not always find the same low energy shape because there are so many possibilities.

A trajectory may consist of two stages. The first stage uses a simplified representation of amino acids which allows us to try many different possible shapes rapidly. This stage is regarded as a low resolution search and on the screen saver you will see the protein chain jumping around a lot. In the second stage, Rosetta uses a full representation of amino acids. This stage is refered to as “relaxation.” Instead of moving around a lot, the protein tries smaller changes in an attempt to move the amino acids to their correct arrangment. This stage is regarded as a high resolution search and on the screen saver, you will see the protein chain jiggle around a little. Rosetta can do the first stage in a few minutes on a modern computer. The second stage takes longer because of the increased complexity when considering the full representation (all atoms) of amino acids.

Your computer typically generates 5-20 of these trajectories (per work unit) and then sends us back the lowest energy shape seen in each one. We then look at all of the low energy shapes, generated by all of your computers, to find the very lowest ones. This becomes our prediction for the fold of that protein.

To join this project, download and install the BOINC software on which it runs. Then attach to the project. While you are at BOINC, look at some of the other projects to see what else might be of interest to you.

U Washington Dr. David Baker

My BOINC

From BNL via Interactions.org: “Relativistic Heavy Ion Collider Begins 18th Year of Experiments”

Brookhaven Lab

Interactions.org

21 March 2018

Media and Communications Office
Peter Genzer
+ 1 631 344 5056
genzer@bnl.gov

The first smashups of two new types of particles at the Relativistic Heavy Ion Collider (RHIC —a U.S. Department of Energy (DOE) Office of Science user facility for nuclear physics research at Brookhaven National Laboratory—will offer fresh insight into the effects of magnetism on the fireball of matter created in these collisions. Accomplishing this main goal of the 15-week run of RHIC’s 18th year will draw on more than a decade of accumulated expertise, enhancements to collider and detector components, and a collaborative effort with partners across the DOE complex and around the world.

Physicists will also perform two different kinds of collisions with gold ions at low energies, including collisions of gold ions with a stationary target. These collisions will help scientists better understand the exotic matter created in RHIC’s highest energy collisions, including the strength of its magnetic field and how it evolves from a hot soup of matter’s fundamental building blocks (quarks and gluons) to the ordinary protons and neutrons that make up the bulk of visible matter in the universe today.

As an added bonus—or rather, a testament to the efficiency of RHIC accelerator staff—the collider-accelerator team will also be implementing and fine-tuning several technologies important for future nuclear physics research.

“In some ways this run is the culmination of two decades of facility development,” said Wolfram Fischer, Associate Chair for Accelerators in Brookhaven Lab’s Collider-Accelerator (C-AD) Department. “We will make use of many tools we have developed over many years, which we now need all at the same time. All this expertise in C-AD and support from DOE and other labs came together to make this possible.”

Helen Caines, a physicist at Yale University who serves as co-spokesperson for RHIC’s STAR experiment, agreed and expressed her appreciation for RHIC’s unique versatility and ability to pack in so much in such a short time. “It’s going to be a busy 15 weeks!” she said.

Studying magnetic effects

RHIC collides ions (for example, the nuclei of heavy atoms such as gold that have been stripped of their electrons) to “melt” their protons and neutrons and set free those particles’ internal building blocks, known as quarks and gluons. Creating this “quark-gluon plasma” mimics the conditions of the very early universe and gives scientists a way to explore the force that governs how these fundamental particles interact. The nuclear physicists conduct these studies by tracking the particles emerging from the collisions.

One intriguing finding from an earlier run at RHIC was an observation of differences in how negatively and positively charged particles flow out from the fireball created when two gold ions collide. Scientists suspect that this charge separation is triggered in part by something called the “chiral magnetic effect”—an interaction between the powerful magnetic field generated when the positively charged ions collide slightly off center (producing a swirling mass of charged matter) and each individual particle’s “chirality”. Chirality is a particle’s right- or left-handedness, which depends on whether it is spinning clockwise or counterclockwise relative to its direction of motion. According to this understanding, the charge separation should get stronger as the strength of the magnetic field increases—which is exactly what STAR scientists are testing in Run 18.

“Instead of gold, we are using collisions with two different ‘isobars’—isotopes of atoms that have the same mass but different numbers of protons, and therefore different levels of positive charge,” said Caines. Collisions of two ruthenium ions (mass number 96 with 44 protons) will create a magnetic field that’s 10 percent stronger than collisions of two zirconium ions (mass number 96 with only 40 protons), she said.

“We are keeping everything else the same—the size of nucleus, the energy, and the total number of particles participating in the collision. We’ll even be switching from one ion species to the other on close to a day-by-day basis to eliminate any variation running the two types of collisions weeks apart might cause. Since the only thing we are varying is the magnetic field, this should be a definitive test of the chiral magnetic effect.”

A positive result would prove that the collisions are creating a very strong magnetic field—”the strongest ever observed,” Caines said. “It would also be definitive proof that the collisions are creating a medium made up of free quarks and gluons, a quark-gluon plasma, with an imbalance of left- and right-handed particles driven by quantum fluctuations.”

Obtaining and prepping the isotopes

Though the amount of matter needed to collide individual ions is extremely small (RHIC will use much less than a gram of gold in all its years of operation!), obtaining certain rare isotopes can be challenging. Zirconium-96 (the form needed for these experiments) makes up less than three percent of the naturally occurring supply of this element, while ruthenium-96 makes up less than six percent.

“If you just used natural material for the ion sources that feed RHIC, the beam intensity would be way too low to collect the data needed,” said Fischer. “You can buy enriched samples of zirconium but there is no commercial source of enriched ruthenium.”

Fortunately, there is a new facility for such isotope enrichment at DOE’s Oak Ridge National Laboratory (ORNL), the Enriched Stable Isotope Prototype Plant (ESIPP), which heated up the natural material and electromagnetically separated out the different masses. ESIPP is part of the DOE Isotope Program and started operations in FY 2018, re-establishing a general domestic capability to enrich stable isotopes.

“With the help of the DOE Isotope Program in the Office of Science, ORNL put us at the top of their priority list to provide one-half gram of this material—a little vial with a bit of ‘dust’ in the bottom—in time for the run,” Fischer said.

The ruthenium ions start their path of acceleration in Brookhaven’s Tandem Van De Graaff accelerator. So as not to waste any of the precious ion supply, the Tandem team, led by Peter Thieberger, first ran tests with higher-abundance forms of ruthenium, making sure they’d have the beam intensity needed. For the actual experiments, they dilute the ruthenium sample with aluminum to spread out the supply. Once accelerated, the ions get bunched and those bunches get combined into more and more tightly pack bunches as they circulate through the Booster ring and the Alternating Gradient Synchrotron (AGS), gaining energy at each step before being injected into RHIC’s two counter-circulating 2.4-mile-circumference rings for collisions at 200 billion electron volts (GeV).

To get the zirconium ions for collisions on the alternating days, the Brookhaven team, led by Masahiro Okamura, sought help from Hiromitsu Haba and colleagues at Japan’s RIKEN laboratory who’d had experience with zirconium targets. “They generously shared everything they know about transforming zirconium into oxide targets we could use to extract the ions,” Fischer said.

Scientists zap these zirconium oxide targets with a laser at Brookhaven’s Laser Ion Source to create a plasma containing positively charged zirconium ions. Those ions then enter the Electron Beam Ion Source (EBIS) to be transformed into a beam. From EBIS, the zirconium beam follows a path similar to that of ruthenium, with the ions merging into tighter and tighter bunches and gaining energy in the Booster and AGS before being injected into RHIC. Yet another team—Brookhaven’s own chemists from the Medical Isotope Research and Production Program, led by Cathy Cutler—recovers leftover target material and reprocess it to make new targets so that no valuable isotope material is left unused.

Having the two types of ions enter RHIC from different sources makes it easier to switch from ruthenium to zirconium day by day. “These are two somewhat exotic species of ions, so we wanted two independent sources that can be optimized and run independently,” Fischer said. “If you run both out of one source, it’s harder to get the best performance out of both of them.”

Once either set of ions enters the collider, additional enhancements made at RHIC over the years help maximize the number of data-producing collisions. Most significantly, a technique called “stochastic cooling”, implemented during this run by Kevin Mernick, detects when particles within the beams spread out (heat up), and sends corrective signals to devices ahead of the speeding ions to nudge them back into tight packs.

“Without stochastic cooling it would be very hard if not impossible to reach the experimental goals because we would lose a lot of ions,” Fischer said. “And we couldn’t do this without all the different parts in DOE and at Brookhaven. We needed all our source knowledge in EBIS and at the Tandem, and we needed collaborators from RIKEN, ORNL, and our chemists in the Isotope Program at Brookhaven as well. It’s been an amazing collaborative effort.”

“Switching from one species to another every day has never been done before in a collider,” Fischer said. “Greg Marr, the RHIC Run Coordinator this year, needs to draw on all tools available to make these transitions as quickly and seamlessly as possible.”

More to learn from gold-gold

Following the isobar run, STAR physicists will also study two kinds of gold-gold collisions. First, in collisions of gold beams at 27 GeV, they will look for differential effects in how particles called lambdas and oppositely charged antilambda particles emerge. Tracking lambdas recently led to the discovery that RHIC’s quark-gluon plasma is the fastest spinning fluid ever encountered. Measuring the difference in how lambdas and their antiparticle counterparts behave would give STAR scientists a precise way to measure the strength of the magnetic field that causes this “vorticity.”

“This will help us improve our calculations of the chiral magnetic effect because we would have an actual measurement of the magnetic contribution. Until now, those values have been based purely on theoretical calculations,” Caines said.

In the final phase of the run, accelerator physicists will configure RHIC to run as a fixed-target experiment. Instead of crashing two beams together in head-on collisions, they will slam one beam of gold ions into a gold foil placed within the STAR detector. The center of mass collision energy, 3.2 GeV, will be lower than in any previous RHIC run. These collisions will test to see if a signal the scientists saw at higher energies—large fluctuations in the production of protons— turns off. The disappearance of this signal could indicate that the fluctuations observed at higher energies were associated with a so-called “critical point” in the transition of free quarks and gluons to ordinary matter []. The search for this point—a particular set of temperature and pressure conditions where the type of phase transformation changes—has been another major research goal at RHIC.

These lowest energy collisions will also form the start of the next “beam energy scan,” a series of collisions across a wide range of energies beginning in earnest next year, Caines said. That work will build on results from earlier efforts to map the various phases of quark-gluon matter.

Tuning up detector and accelerator technologies

Some newly upgraded components of the STAR detector will be essential to these and future studies of nuclear matter at RHIC, so STAR physicists will be closely monitoring their performance during this run. These include:

• An inner component of the barrel-shaped Time Projection Chamber (the iTPC), developed with significant support from DOE and China’s National Natural Science Foundation and Ministry of Science and Technology.
• An “endcap time of flight” (eTOF) detector developed by STAR physicists and a collaboration of scientists working on the Compressed Baryonic Matter experiment, which will be located at the future Facility for Antiproton and Ion Research in Darmstadt, Germany.
• A new “event plane detector” developed by U.S. and Chinese collaborators in a project supported by the DOE, the U.S. National Science Foundation, and the Chinese Ministry of Science and Technology.

The first two of these components work together to track and identify particles emerging from collisions closer to the beamline than ever before, enabling physicists to more precisely study directional preferences of particles. The event plane detector will track the orientation of the overlap region created by colliding particles—and therefore the orientation of the magnetic field.

“The combination of these new components will enhance our ability to track and identify particles and study how the patterns of particles produced are influenced by collision conditions,” Caines said.

On the accelerator front, Fischer notes two major efforts taking place in parallel with the Run 18 physics studies.

One project is commissioning a newly installed electron accelerator for low energy electron cooling, an effort led by Alexei Fedotov. This major new piece of equipment uses a green-laser-triggered photocathode electron gun to produce a cool beam of electrons. The electrons get injected into a short section of each RHIC ring to mix with the ion beams and extract heat, which reduces spreading of the ions at low energies to maximize collision rates.

The commissioning will include fine tuning the photocathode gun and the radiofrequency (RF) cavities that accelerate the electron beam after it leaves the gun to get it up to speed of RHIC’s gold beams. The physicists will also commission RF correctors that give extra kicks to lagging particles and slow down those that are too speedy to keep all the electrons closely spaced.

“We have to make sure the electron beam has all the necessary properties—energy, size, momentum spread, and current—to cool the ion beam,” Fischer said. “If everything goes right, then we can use this system to start cooling the gold beam next year.”

Physicists will also test another system for electron cooling at higher energies, which was developed in an effort led by Vladimir Litvinenko. In this system, called coherent electron cooling, electron beams are used as sensors for picking up irregularities in the ion beam. “The electron beam gets ‘imprinted’ by regions of low or high ion density,” Fischer said. Once amplified, this signal in the electron beam can be fed back to the ion beam “out of phase” to smooth out the irregularities.

Though this type of cooling is not essential to the research program at RHIC, it would be essential for cooling beams in a high-energy Electron-Ion Collider (EIC), a possible future research facility that nuclear physicists hope to build. Testing the concept at RHIC helps lay the foundation for how it would work at an EIC, Fischer said.

If the experience at RHIC is any guide, all the testing should pay off with future physics discoveries.

BNL RHIC Campus

BNL/RHIC Star Detector

BNL RHIC PHENIX

One of ten national laboratories overseen and primarily funded by the Office of Science of the U.S. Department of Energy (DOE), Brookhaven National Laboratory conducts research in the physical, biomedical, and environmental sciences, as well as in energy technologies and national security. Brookhaven Lab also builds and operates major scientific facilities available to university, industry and government researchers. The Laboratory’s almost 3,000 scientists, engineers, and support staff are joined each year by more than 5,000 visiting researchers from around the world. Brookhaven is operated and managed for DOE’s Office of Science by Brookhaven Science Associates, a limited-liability company founded by Stony Brook University, the largest academic user of Laboratory facilities, and Battelle, a nonprofit, applied science and technology organization.

See the full article here .

Please help promote STEM in your local schools.

Stem Education Coalition

From SLAC: “Weird Superconductor Leads Double Life”

SLAC Lab

March 20, 2018
Glennda Chui

One unusual property of superconducting materials is that they expel magnetic fields and thus cause magnets to levitate, as shown here. A study at SLAC and Stanford of a particularly odd superconductor, strontium titanate, will aid understanding and development of these materials. (ViktorCap/iStock)

Understanding strontium titanate’s odd behavior will aid efforts to develop materials that conduct electricity with 100 percent efficiency at higher temperatures.

Until about 50 years ago, all known superconductors were metals. This made sense, because metals have the largest number of loosely bound “carrier” electrons that are free to pair up and flow as electrical current with no resistance and 100 percent efficiency – the hallmark of superconductivity.

Then an odd one came along – strontium titanate, the first oxide material and first semiconductor found to be superconducting. Even though it doesn’t fit the classic profile of a superconductor – it has very few free-to-roam electrons – it becomes superconducting when conditions are right, although no one could explain why.

Now scientists have probed the superconducting behavior of its electrons in detail for the first time. They discovered it’s even weirder than they thought. Yet that’s good news, they said, because it gives them a new angle for thinking about what’s known as “high temperature” superconductivity, a phenomenon that could be harnessed for a future generation of perfectly efficient power lines, levitating trains and other revolutionary technologies.

The research team, led by scientists at the Department of Energy’s SLAC National Accelerator Laboratory and Stanford University, described their study in a paper published Jan. 30 in the Proceedings of the National Academy of Sciences.

“If conventional metal superconductors are at one end of a spectrum, strontium titanate is all the way down at the other end. It has the lowest density of available electrons of any superconductor we know about,” said Adrian Swartz, a postdoctoral researcher at the Stanford Institute for Materials and Energy Science (SIMES) who led the experimental part of the research with Hisashi Inoue, a Stanford graduate student at the time.

“It’s one of a large number of materials we call ‘unconventional’ superconductors because they can’t be explained by current theories,” Swartz said. “By studying its extreme behavior, we hope to gain insight into the ingredients that lead to superconductivity in these unconventional materials, including the ones that operate at higher temperatures.”

Dueling Theories

According to the widely accepted theory known as BCS for the initials of its inventors, conventional superconductivity is triggered by natural vibrations that ripple through a material’s atomic latticework. The vibrations cause carrier electrons to pair up and condense into a superfluid, which flows through the material with no resistance – a 100-percent-efficient electric current. In this picture, the ideal superconducting material contains a high density of fast-moving electrons, and even relatively weak lattice vibrations are enough to glue electron pairs together.

But outside the theory, in the realm of unconventional superconductors, no one knows what glues the electron pairs together, and none of the competing theories hold sway.

To find clues to what’s going on inside strontium titanate, scientists had to figure out how to apply an important tool for studying superconducting behavior, known as tunneling spectroscopy, to this material. That took several years, said Harold Hwang, a professor at SLAC and Stanford and SIMES investigator.

“The desire to do this experiment has been there for decades, but it’s been a technical challenge,” he said. “This is, as far as I know, the first complete set of data coming out of a tunneling experiment on this material.” Among other things, the team was able to observe how the material responded to doping, a commonly used process where electrons are added to a material to improve its electronic performance.

‘Everything is Upside Down’

The tunneling measurements revealed that strontium titanate is the exact opposite of what you’d expect in a superconductor: Its lattice vibrations are strong and its carrier electrons are few and slow.

“This is a system where everything is upside down,” Hwang said.

On the other hand, details like the behavior and density of its electrons and the energy required to form the superconducting state match what you would expect from conventional BCS theory almost exactly, Swartz said.

“Thus, strontium titanate seems to be an unconventional superconductor that acts like a conventional one in some respects,” he said. “This is quite a conundrum, and quite a surprise to us. We discovered something that was more confusing than we originally thought, which from a fundamental physics point of view is more profound.”

He added, “If we can improve our understanding of superconductivity in this puzzling set of circumstances, we could potentially learn how to harvest the ingredients for realizing superconductivity at higher temperatures.”

The next step, Swartz said, is to use tunneling spectroscopy to test a number of theoretical predictions about why strontium titanate acts the way it does.

SIMES is a joint SLAC/Sanford institute. Theorists from SIMES and from the University of Tennessee, Knoxville also contributed to this study, which was funded by the DOE Office of Science and the Gordon and Betty Moore Foundation’s Emergent Phenomena in Quantum Systems Initiative.

See the full article here .

Please help promote STEM in your local schools.

Stem Education Coalition

SLAC is a multi-program laboratory exploring frontier questions in photon science, astrophysics, particle physics and accelerator research. Located in Menlo Park, California, SLAC is operated by Stanford University for the DOE’s Office of Science.

From UCLA: “UCLA researchers develop a new class of two-dimensional materials”

UCLA Newsroom

March 08, 2018
Matthew Chin

An artist’s concept of two kinds of monolayer atomic crystal molecular superlattices. On the left, molybdenum disulfide with layers of ammonium molecules; on the right, black phosphorus with layers of ammonium molecules. UCLA.

A research team led by UCLA scientists and engineers has developed a method to make new kinds of artificial “superlattices” — materials comprised of alternating layers of ultra-thin “two-dimensional” sheets, which are only one or a few atoms thick. Unlike current state-of-the art superlattices, in which alternating layers have similar atomic structures, and thus similar electronic properties, these alternating layers can have radically different structures, properties and functions, something not previously available.

For example, while one layer of this new kind of superlattice can allow a fast flow of electrons through it, the other type of layer can act as an insulator. This design confines the electronic and optical properties to single active layers, and they do not interfere with other insulating layers.

Such superlattices can form the basis for improved and new classes of electronic and optoelectronic devices. Applications include superfast and ultra-efficient semiconductors for transistors in computers and smart devices, and advanced LEDs and lasers.

Compared with the conventional layer-by-layer assembly or growth approach currently used to create 2D superlattices, the new UCLA-led process to manufacture superlattices from 2D materials is much faster and more efficient. Most importantly, the new method easily yields superlattices with tens, hundreds or even thousands of alternating layers, which is not yet possible with other approaches.

This new class of superlattices alternates 2D atomic crystal sheets that are interspaced with molecules of varying shapes and sizes. In effect, this molecular layer becomes the second “sheet” because it is held in place by “van der Waals” forces, weak electrostatic forces to keep otherwise neutral molecules “attached” to each other. These new superlattices are called “monolayer atomic crystal molecular superlattices.”

The study, published in Nature, was led by Xiangfeng Duan, UCLA professor of chemistry and biochemistry, and Yu Huang, UCLA professor of materials science and engineering at the UCLA Samueli School of Engineering.

“Traditional semiconductor superlattices can usually only be made from materials with highly similar lattice symmetry, normally with rather similar electronic structures,” Huang said. “For the first time, we have created stable superlattice structures with radically different layers, yet nearly perfect atomic-molecular arrangements within each layer. This new class of superlattice structures has tailorable electronic properties for potential technological applications and further scientific studies.”

One current method to build a superlattice is to manually stack the ultrathin layers one on top of the other. But this is labor-intensive. In addition, since the flake-like sheets are fragile, it takes a long time to build because many sheets will break during the placement process. The other method is to grow one new layer on top of the other, using a process called “chemical vapor deposition.” But since that means different conditions, such as heat, pressure or chemical environments, are needed to grow each layer, the process could result in altering or breaking the layer underneath. This method is also labor-intensive with low yield rates.

The new method to create monolayer atomic crystal molecular superlattices uses a process called “electrochemical intercalation,” in which a negative voltage is applied. This injects negatively charged electrons into the 2D material. Then, this attracts positively charged ammonium molecules into the spaces between the atomic layers. Those ammonium molecules automatically assemble into new layers in the ordered crystal structure, creating a superlattice.

“Think of a two-dimensional material as a stack of playing cards,” Duan said. “Then imagine that we can cause a large pile of nearby plastic beads to insert themselves, in perfect order, sandwiching between each card. That’s the analogous idea, but with a crystal of 2D material and ammonium molecules.”

The researchers first demonstrated the new technique using black phosphorus as a base 2D atomic crystal material. Using the negative voltage, positively charged ammonium ions were attracted into the base material, and inserted themselves between the layered atomic phosphorous sheets.

Following that success, the team inserted different types of ammonium molecules with various sizes and symmetries into a series of 2D materials. They found that they could tailor the structures of the resulting monolayer atomic crystal molecular superlattices, which had a diverse range of desirable electronic and optical properties.

“The resulting materials could be useful for making faster transistors that consume less power, or for creating efficient light-emitting devices,” Duan said.

The lead author of the study is Chen Wang, a doctoral student advised by Huang and Duan, who are both members of the California NanoSystems Institute. Other study authors are UCLA graduate students and postdoctoral researchers in Duan or Huang’s research groups; researchers from Caltech; Hunan University, China; University of Science and Technology of China; and King Saud University, Saudi Arabia.

The research was supported by the National Science Foundation and the Office of Naval Research.

See the full article here .

Please help promote STEM in your local schools.

Stem Education Coalition

For nearly 100 years, UCLA has been a pioneer, persevering through impossibility, turning the futile into the attainable.

We doubt the critics, reject the status quo and see opportunity in dissatisfaction. Our campus, faculty and students are driven by optimism. It is not naïve; it is essential. And it has fueled every accomplishment, allowing us to redefine what’s possible, time after time.

This can-do perspective has brought us 12 Nobel Prizes, 12 Rhodes Scholarships, more NCAA titles than any university and more Olympic medals than most nations. Our faculty and alumni helped create the Internet and pioneered reverse osmosis. And more than 100 companies have been created based on technology developed at UCLA.

From PI: Women in STEM-“Celebrating International Women’s Day”

Is it not a shame that we need to have a special day to celebrate women when they are so already fantastic and exceptionally brilliant in the physical sciences?

Check out this blog post-
https://sciencesprings.wordpress.com/2018/03/08/from-the-conversation-women-in-stem-perish-not-publish-new-study-quantifies-the-lack-of-female-authors-in-scientific-journals/

“”I have done a couple of STEM events, but there have never been this many girls. There are so many here. It is really empowering. Go girls in STEM!” Eama, Grade 12

Today’s Inspiring Future Women in Science conference was a success. Mona Nemar, Canada’s Chief Science Advisor, gave opening remarks encouraging the students in attendance to take advantage of the opportunity to learn from the speakers to come.

“The days of women being held back or being excluded from science are over. Now, more than ever women are entering, remaining in, and revolutionizing the science fields. Today is a shining example of that.”
-Mona Nemar, Chief Science Advisor, Government of Canada

Mona, read my above post on women getting not published.

The speakers and panelists, who included a chemist, engineer, astronomer, ecologist, and surgeon, talked about the challenges and triumphs that a career in STEM brings. Students were then treated to a speed mentoring session where they were able to ask questions and interact with women from a broad number of STEM careers. Read more about how this conference is inspiring young women here.

“This conference showed me there are so many things you can do going into [a career in STEM], so now I feel more inspired, and I feel more confident and not scared to go into science.” Lealan, Age 16

Programs like Perimeter’s “Inspiring Future Women in Science” conference are helping young women see their own potential and reach out for careers in STEM. And more talented female scientists today, means a brighter future tomorrow.

Thank you for being part of the equation.

From Science: “Superconducting materials found in meteorites”

Science Magazine

Mar. 6, 2018
Adrian Cho

This 9980-kilogram meteorite, which crashed into Australia, contains tiny amounts of natural superconducting material, physicists have found.
Sydney Oats/Wikimedia commons (CC BY 2.0)

Meteorites sometimes contain naturally occurring superconductors, materials that conduct electricity without any resistance, a team of physicists has found. The result, reported here today at the annual March meeting of the American Physical Society, won’t revolutionize scientists’ understanding of the solar system, but it could raise hopes of finding a material that is a superconductor a room temperature—which could potentially lead to technological breakthroughs such as magnetically levitating trains.

“It sounds like they found something and isolated it,” says Johnpierre Paglione, a condensed matter physicist at the University of Maryland in College Park, whose team is screening naturally occurring terrestrial minerals.

Conventional superconductors consist of simple metals, such as niobium, lead, or mercury, which become superconducting when cooled to below a characteristic “critical temperature” close to absolute zero—4.2 K in the case of mercury. In 1986, physicists discovered a family of copper-containing compounds that superconduct at temperatures as high as 134 K (–139°C)—a phenomenon known as high-temperature superconductivity whose origins remain one of the biggest mysteries in science. More recently, researchers have found a family of high-temperature iron-based superconductors, and there are myriad other exotic superconductors as well.

Although many scientists strive to synthesize novel superconductors by designing particular properties from the atomic scale up, a team led by Ivan Schuller, a condensed matter physicist at the University of California, San Diego (UCSD), decided to screen existing materials, starting with meteorites. “There are all these materials that God has provided,” Schuller says. “Why not look at them? ”Meteorites form under extreme temperatures and pressures beyond the capabilities of any laboratory on Earth. Thus, they’re fertile places to search for exotic new compounds, Schuller says.

The surest sign of superconductivity is a sudden plunge to zero in electrical resistance when the temperature drops below a critical threshold. But a superconductor has peculiar magnetic properties, too: It can repel an applied magnetic field if it is not too strong because free-flowing currents, swirling within the material, produce a field that cancels the applied one. The phenomenon is known as the Meissner effect, and physicists also try to find new superconductors by looking for it, especially in heterogeneous samples that are only speckled with bits of superconductor and in which the resistance never goes to zero.

However, that technique is not sensitive enough to look for very small amount of superconductor, Schuller says. So, his team put a twist on it to effectively amplify the signal. Both above and below its critical temperature a superconductor can absorb microwaves, but right at the transition the absorption changes.

To look for superconductivity, Schuller’s team placed a small sample within a cavity pumped with microwave radiation. The scientists applied both a strong constant magnetic field and a small oscillating magnetic field. When they cool a superconductor through its critical temperature, the absorption changes dramatically, explains James Wampler, a graduate student at UCSD who presented the results at the meeting. The signal is greatly enhanced, he explains, as the oscillating magnetic field drives the material in and out of superconductivity. The technique is about 1000 times more sensitive than conventional magnetic measurements, Wampler says.

The researchers validated their technique on thousands of samples of materials, Schuller says. And now, they have applied it to small samples scraped from the surfaces of 16 different meteorites, Wampler said at the meeting. They found evidence of superconductivity in samples from two of those meteorites: the Mundrabilla meteorite, a 9980-kilogram chunk of iron discovered in the Australian Outback in 1911, and Graves Nunataks, a carbonaceous meteorite found in Antarctica in 1995.

Once the researchers found the positive magnetic signal, they visually teased out the different types of grains in each powdered sample and used x-ray spectroscopy to identify the materials in the grains that were superconductive. The superconductor in the Grave Nunataks meteorite is an alloy of indium and tin, Wampler says. The one in the Mundrabilla meteorite appears to be an alloy of indium, tin, and possibly lead. Both are well-known superconductors that have critical temperatures around 5 K.

Even though the superconductors aren’t exotic, the results show that superconductivity is ubiquitous in the universe, Wampler says “If this is in meteorites, it’s everywhere,” he says. He declines to speculate on the implications for astrophysics, but notes “there are lots of places in the universe colder than 5 K.” Meteorites are generated at pressures and temperatures exceeding lab conditions, Wampler notes, so the ultimate hope is that they may contain superconducting compounds unknown to humans.

Paglione agrees that the field needs to find new materials. “There’s a community of people who are looking for new materials,” he says, “but it’s a bottleneck.”

*Correction, 7 March, 11:51 a.m.: The story has been updated to make it clear which types of samples Ivan Schuller and Johnpierre ​Paglione have studied.

See the full article here .

Please help promote STEM in your local schools.

Stem Education Coalition

From Rice: “Dressing atoms in an ultracold soup”

Rice University

February 28, 2018
Jade Boyd

Physicists build bizarre molecules called ‘Rydberg polarons’

Using lasers, U.S. and Austrian physicists have coaxed ultracold strontium atoms into complex structures unlike any previously seen in nature.

“I am amazed that we’ve discovered a new way that atoms assemble,” said Rice University physicist Tom Killian. “It shows how rich the laws of physics and chemistry can be.” Killian is the lead scientist on a new paper in Physical Review Letters that summarized the group’s experimental findings.

Killian teamed with experimental physicists from Rice’s Center for Quantum Materials and theoretical physicists from Harvard University and Vienna University of Technology on the two-year project to create “Rydberg polarons” out of strontium atoms that were at least 1 million times colder than deep space.

The team’s findings, which are summarized in the PRL paper and a companion theoretical study appearing this week in Physical Review A, reveal something new about the basic nature of matter, Killian said.

“The basic laws that we learn in chemistry class tell us how atoms bond together to form molecules, and a deep understanding of those principles is what allows chemists and engineers to make the materials we use in our everyday lives,” he said. “But those laws are also quite rigid. Only certain combinations of atoms will form stable bonds in a molecule. Our work explored a new type of molecule that isn’t described by any of the traditional rules for binding atoms together.”

Rice University physicists (clockwise from left) Soumya Kanungo, Tom Killian, Roger Ding, Barry Dunning and Joe Whalen used lasers and an ultracold strontium gas to make “Rydberg polarons,” complex molecules unlike any previously seen in nature. (Photo by Jeff Fitlow/Rice University)

Killian said the new molecules are only stable at extraordinarily cold temperatures — about a millionth of a degree above absolute zero. At such low temperatures, the constituent atoms stay still long enough to become “glued together” in new, complex structures, he said.

“One amazing thing is that you can keep attaching an arbitrary number of atoms to these molecules,” Killian said. “It’s just like attaching Lego blocks, which you can’t do with traditional types of molecules.”

He said the discovery will be of interest to theoretical chemists, condensed matter physicists, atomic physicists and physicists who are studying Rydberg atoms for potential use in quantum computers.

“Nature takes advantage of a fascinating toolbox of tricks for binding atoms together to make molecules and materials,” Killian said. “As we discover and understand these tricks, we satisfy our innate curiosity about the world we live in, and it can often lead to practical advances like new therapeutic drugs or light-harvesting solar cells. It is too early to tell if any practical applications will come from our work, but basic research like this is what it takes to find tomorrow’s great breakthroughs.”

The team’s efforts centered around making, measuring and predicting the behavior of a specific state of matter called a Rydberg polaron, a combination of two distinct phenomena, Rydberg atoms and polarons.

In Rydberg atoms, one or more electrons are excited with a precise amount of energy so that they orbit far from the atom’s nucleus. Rydberg atoms can be described with simple rules written down more than a century ago by Swedish physicist Johannes Rydberg. They have been studied in laboratories for decades and are believed to exist in cold reaches of deep space. The Rydberg atoms in the PRL study were up to one micron wide, about 1,000 times larger than normal strontium atoms.

Rice University atomic physicist Joe Whalen works on a laser cooling system for ultracold strontium gas. (Photo by Jeff Fitlow/Rice University)

Polarons are created when a single particle interacts strongly with its environment and causes nearby electrons, ions or atoms to rearrange themselves and form a sort of coating that the particle carries with it. The polaron itself is a collective — a unified object known as a quasiparticle — that incorporates properties of the original particle and its environment.

Rydberg polarons are a new class of polarons in which the high-energy, far-orbiting electron gathers hundreds of atoms within its orbit as it moves through a dense, ultracold cloud. In the Rice experiments, researchers began by creating a supercooled cloud of several hundred thousand strontium atoms. By coordinating the timing of laser pulses with changes in the electric field, the researchers were able to create and count Rydberg polarons one by one, ultimately forming millions of them for their study.

While Rydberg polarons had previously been created with rubidium, the use of strontium allowed the physicists to more clearly resolve the energy of the coated Rydberg atoms in a way that revealed previously unseen universal characteristics.

“I give a lot of credit to the theorists,” said Killian, a professor of physics and astronomy. “They developed powerful techniques to calculate the structure of hundreds of interacting particles in order to interpret our results and identify the signatures of the Rydberg polarons.

“From an experimental standpoint, it was challenging to make and measure these polarons,” he said. “Each one lived for only a few microseconds before collisions with other particles tore it apart. We had to use very sensitive techniques to count these fragile and fleeting objects.”

Study co-authors include Joe Whalen, Roger Ding and Barry Dunning, all of Rice; Francisco Camargo, formerly of Rice and now of AMD; Germano Woehl Jr., formerly of Rice and now of the University of the São Paulo; Shuhei Yoshida and Joachim Burgdörfer of Vienna University of Technology; Hossein Sadeghpour of the Harvard-Smithsonian Center for Astrophysics; and Richard Schmidt and Eugene Demler of Harvard University.

The research was supported by the Air Force Office of Scientific Research, the National Science Foundation, the Robert A. Welch Foundation, the Austrian Science Fund, the Army Research Office, Dr. Max Rössler, the Walter Haefner Foundation and the ETH Foundation.

See the full article here .

Please help promote STEM in your local schools.

Stem Education Coalition

In his 1912 inaugural address, Rice University president Edgar Odell Lovett set forth an ambitious vision for a great research university in Houston, Texas; one dedicated to excellence across the range of human endeavor. With this bold beginning in mind, and with Rice’s centennial approaching, it is time to ask again what we aspire to in a dynamic and shrinking world in which education and the production of knowledge will play an even greater role. What shall our vision be for Rice as we prepare for its second century, and how ought we to advance over the next decade?

This was the fundamental question posed in the Call to Conversation, a document released to the Rice community in summer 2005. The Call to Conversation asked us to reexamine many aspects of our enterprise, from our fundamental mission and aspirations to the manner in which we define and achieve excellence. It identified the pressures of a constantly changing and increasingly competitive landscape; it asked us to assess honestly Rice’s comparative strengths and weaknesses; and it called on us to define strategic priorities for the future, an effort that will be a focus of the next phase of this process.