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Chemists ID Catalytic 'Key' for Converting CO2 to Methanol

Results from experiments and computational modeling studies that definitively identify the "active site" of a catalyst commonly used for making methanol from CO2 will guide the design of improved catalysts for transforming this pollutant to useful chemicals.

Cryo-Electron Microscopy Achieves Unprecedented Resolution Using New Computational Methods

Cryo-electron microscopy (cryo-EM)--which enables the visualization of viruses, proteins, and other biological structures at the molecular level--is a critical tool used to advance biochemical knowledge. Now Berkeley Lab researchers have extended cryo-EM's impact further by developing a new computational algorithm instrumental in constructing a 3-D atomic-scale model of bacteriophage P22 for the first time.

New Study Maps Space Dust in 3-D

A new Berkeley Lab-led study provides detailed 3-D views of space dust in the Milky Way, which could help us understand the properties of this dust and how it affects views of distant objects.

Single-Angle Ptychography Allows 3D Imaging of Stressed Materials

Scientists have used a new X-ray diffraction technique called Bragg single-angle ptychography to get a clear picture of how planes of atoms shift and squeeze under stress.

New Feedback System Could Allow Greater Control Over Fusion Plasma

A physicist has created a new system that will let scientists control the energy and rotation of plasma in real time in a doughnut-shaped machine known as a tokamak.

Towards Super-Efficient, Ultra-Thin Silicon Solar Cells

Researchers from Ames Laboratory used supercomputers at NERSC to evaluate a novel approach for creating more energy-efficient ultra-thin crystalline silicon solar cells by optimizing nanophotonic light trapping.

Study IDs Link Between Sugar Signaling and Regulation of Oil Production in Plants

UPTON, NY--Even plants have to live on an energy budget. While they're known for converting solar energy into chemical energy in the form of sugars, plants have sophisticated biochemical mechanisms for regulating how they spend that energy. Making oils costs a lot. By exploring the details of this delicate energy balance, a group of scientists from the U.

High-Energy Electrons Probe Ultrafast Atomic Motion

A new technique synchronized high-energy electrons with an ultrafast laser pulse to probe how vibrational states of atoms change in time.

Rare Earth Recycling

A new energy-efficient separation of rare earth elements could provide a new domestic source of critical materials.

Two-Dimensional MXene Materials Get Their Close-Up

Researchers have long sought electrically conductive materials for economical energy-storage devices. Two-dimensional (2D) ceramics called MXenes are contenders.


Three SLAC Employees Awarded Lab's Highest Honor

At a March 7 ceremony, three employees of the Department of Energy's SLAC National Accelerator Laboratory were awarded the lab's highest honor ­- the SLAC Director's Award.

Dan Sinars Represents Sandia in First Energy Leadership Class

Dan Sinars, a senior manager in Sandia National Laboratories' pulsed power center, which built and operates the Z facility, is the sole representative from a nuclear weapons lab in a new Department of Energy leadership program that recently visited Sandia.

ORNL, HTS International Corporation to Collaborate on Manufacturing Research

HTS International Corporation and the Department of Energy's Oak Ridge National Laboratory have signed an agreement to explore potential collaborations in advanced manufacturing research.

Jefferson Lab Director Honored with Energy Secretary Award

Hugh Montgomery, director of the Department of Energy's Thomas Jefferson National Accelerator Facility (Jefferson Lab), was awarded The Secretary's Distinguished Service Award by the Secretary of Energy earlier this year.

New Projects to Make Geothermal Energy More Economically Attractive

Geothermal energy, a clean, renewable source of energy produced by the heat of the earth, provides about 6 percent of California's total power. That number could be much higher if associated costs were lower. Now scientists at the Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab) have launched two California Energy Commission-funded projects aimed at making geothermal energy more cost-effective to deploy and operate.

Southern Research Project Advances Novel CO2 Utilization Strategy

The U.S. Department of Energy's Office of Fossil Energy has awarded Southern Research nearly $800,000 for a project that targets a more cost-efficient and environmentally friendly method of producing some of the most important chemicals used in manufacturing.

Harker School Wins 2017 SLAC Regional Science Bowl Competition

After losing its first match of the day to the defending champions, The Harker School's team won 10 consecutive rounds to claim victory in the annual SLAC Regional DOE Science Bowl on Saturday, Feb. 11.

Francis Alexander Named Deputy Director of Brookhaven Lab's Computational Science Initiative

Alexander brings extensive management and leadership experience in computational science research to the position.

Kalinin, Paranthaman Elected Materials Research Society Fellows

Two researchers at Oak Ridge National Laboratory, Sergei Kalinin and Mariappan Parans Paranthaman, have been elected fellows of the Materials Research Society.

Two PNNL Researchers Elected to Membership in the National Academy of Engineering

Two scientists at the Pacific Northwest National Laboratory will become members of the prestigious National Academy of Engineering.


High-Energy Electrons Probe Ultrafast Atomic Motion

A new technique synchronized high-energy electrons with an ultrafast laser pulse to probe how vibrational states of atoms change in time.

Rare Earth Recycling

A new energy-efficient separation of rare earth elements could provide a new domestic source of critical materials.

Modeling the "Flicker" of Gluons in Subatomic Smashups

A new model identifies a high degree of fluctuations in the glue-like particles that bind quarks within protons as essential to explaining proton structure.

Rare Nickel Atom Has "Doubly Magic" Structure

Supercomputing calculations confirm that rare nickel-78 has unusual structure, offering insights into supernovas.

Microbial Activity in the Subsurface Contributes to Greenhouse Gas Fluxes

Natural carbon dioxide production from deep subsurface soils contributes significantly to emissions, even in a semiarid floodplain.

Stretching a Metal Into an Insulator

Straining a thin film controllably allows tuning of the materials' magnetic, electronic, and catalytic properties, essential for new energy and electronic devices.

How Moisture Affects the Way Soil Microbes Breathe

Study models soil-pore features that hold or release carbon dioxide.

ARM Data Is for the Birds

Scientists use LIDAR and radar data to study bird migration patterns, thanks to the Atmospheric Radiation Measurement (ARM) Climate Research Facility.

The Future of Coastal Flooding

Better storm surge prediction capabilities could help reduce the impacts of extreme weather events, such as hurricanes.

Estimating Global Energy Use for Water-Related Processes

Scientists find that water-related energy consumption is increasing across the globe, with pronounced differences across regions and sectors.


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Neutrons Identify Key Ingredients of the Quantum Spin Liquid Recipe

Article ID: 666235

Released: 2016-12-09 11:05:44

Source Newsroom: Oak Ridge National Laboratory

  • Credit: Image credit: ORNL/Jill Hemman

    Red arrows represent electron spin orientations in a portion of the YbMgGaO4 crystal structure, where antiferromagnetic interactions between groups of magnetic moments cause neighboring spins to align anti-parallel to one another. This mechanism is partially responsible for the quantum spin liquid behavior observed in the neutron scattering data, illustrated on the hexagonal tiles.

OAK RIDGE, Tenn., Dec. 9, 2016—Neutron scattering studies of a rare earth metal oxide have identified fundamental pieces to the quantum spin liquid puzzle, revealing a better understanding of how and why the magnetic moments within these materials exhibit exotic behaviors such as failing to freeze into an ordered arrangement even near absolute zero temperatures.

In a paper published in Nature Physics, a team of researchers from the Georgia Institute of Technology, the University of Tennessee and the Department of Energy’s Oak Ridge National Laboratory used neutrons to examine the origins of unusual magnetic behavior in a rare earth–based metal oxide, ytterbium-magnesium-gallium-tetraoxide (YbMgGaO4). The material, discovered in 2015, is known to have strange magnetic properties, putting it in a unique category of materials classified as quantum spin liquids.

“A quantum spin liquid is an exotic state of matter characterized by the entanglement of particles over long distances across the atomic scale,” said lead investigator Martin Mourigal, an assistant physics professor at the Georgia Institute of Technology.

Think of Schrödinger’s cat, the thought experiment, he said: Many particles participate in a quantum superposition, where multiple quantum states combine to form a new quantum state, and cannot be characterized by the behavior of individual particles.

By definition, he said, “it’s something we can’t explain with classical physics.”

In a series of experiments at ORNL’s Spallation Neutron Source, the researchers revealed three key features underpinning the material’s exotic properties:

• antiferromagnetic interactions, where groups of electron spins have an antiparallel alignment with their respective neighbors;

• spin space anisotropy, meaning that individual magnetic moments strongly prefer aligning themselves alongside specific directions in the material; and

• chemical disorder between the material’s magnetic layers that randomizes the interactions between electron spins.

Neutrons are well suited for studying magnetism because their lack of electric charge allows them to penetrate through materials, even when the neutrons’ energy is low. The neutrons also have magnetic moments, allowing researchers to directly probe the behavior of spins within materials.

“Neutron scattering is the only technique that allows us to study the dynamics of quantum spin liquids at the lowest temperatures,” Mourigal said.

However, quantum spin liquids present a challenge because their magnetic moments are constantly changing. In typical materials, researchers can lock the spins into certain symmetric patterns by lowering the temperature of the sample, but this approach doesn’t work on spin liquids.

In the team’s first neutron scattering measurements of an YbMgGaO4 single-crystal sample at the SNS’s Cold Neutron Chopper Spectrometer, CNCS, the researchers observed that, even at a temperature of 0.06 kelvins (approximately negative 460 degrees Fahrenheit), magnetic excitations remained disordered or “fuzzy.” This fluctuating magnetic behavior, known to occur to quantum spin liquids, runs counter to the laws of classical physics.

“The material screamed spin liquid when we put it in the beam,” Mourigal said.

To overcome this fuzziness, the team used an 8 Tesla magnet to create a magnetic field that locked the spins into an ordered and partly frozen arrangement, allowing for better measurements.

“Once we applied the magnetic field, we were able to measure coherent magnetic excitations in the material that propagate sort of like sound waves,” said CNCS instrument scientist Georg Ehlers. “When a neutron comes into the material, it flies by a magnetic moment and shakes it. The nearby magnetic moments see this happening, and they all begin to vibrate in unison. The frequency of these vibrations is determined by the energy between neighboring spins.”

Those magnetic field measurements enabled the team to directly validate theoretical expectations and provided a physical understanding of the spin behavior and the system as a whole.

“A quantum spin liquid is an intrinsically collective state of matter,” said Mourigal. “But if you want to understand the society, you need to understand the individuals as well.”

The team then turned to another SNS instrument, the Fine-Resolution Fermi Chopper Spectrometer instrument, SEQUOIA, to understand the individual properties of the magnetic moments.

“In rare earth magnets, rich physics, like what was observed at the CNCS instrument, can emerge from the fact that the individual spins can prefer to point along certain directions in a crystal,” said SEQUOIA instrument scientist Matthew Stone. “SEQUOIA examined the localized higher energy states to confirm the individual pieces of the model used to describe the CNCS data were correct.”

Mourigal says the information gleaned from the experiments will enable researchers to develop better theoretical models to further study these quantum phenomena.

“While the exact nature of the quantum state hosted by this material has not been fully established yet, we’ve discovered that chemical disorder and other effects are important here,” said Mourigal. “With these experiments, we’ve really been able to nail down what ingredients need to be taken into the recipe for a quantum spin liquid in this material.”

The paper’s authors are Joseph A. M. Paddison, Marcus Daum, Zhiling Dun, Georg Ehlers, Yaohua Liu, Matthew B. Stone, Haidong Zhou and Martin Mourigal.

The YbMgGaO4 sample was synthesized at the University of Tennessee. Supplementary measurements of the YbMgGaO4 crystal structure were made at the SNS CORELLI instrument.

The research received support from the Georgia Institute of Technology, the National Science Foundation, and DOE’s Office of Science. SNS is a DOE Office of Science User Facility.

UT-Battelle manages ORNL for the DOE’s Office of Science. The Office of Science is the single largest supporter of basic research in the physical sciences in the United States and is working to address some of the most pressing challenges of our time. For more information, please visit http://science.energy.gov/.