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Science Highlights

NIST Collaboration Heats Up Exotic Topological Insulators

Fashion is changing in the avant-garde world of next-generation computer component materials. Traditional semiconductors like silicon are releasing their last new lines. Exotic materials called topological insulators (TIs) are on their way in. And when it comes to cool, nitrogen is the new helium.

Move Over, Lasers: Scientists Can Now Create Holograms from Neutrons, Too

For the first time, a team including scientists from the National Institute of Standards and Technology (NIST) have used neutron beams to create holograms of large solid objects, revealing details about their interiors in ways that ordinary laser light-based visual holograms cannot.

The research was a multi-institutional collaboration that included scientists from NIST and the Joint Quantum Institute, a research partnership of NIST and the University of Maryland, as well as North Carolina State University and Canada’s University of Waterloo. The work was published in Optics Express.

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Right Size + Right Chemistry = Right Stuff for Plastics Manufacturing

Plastic manufacturing is an energy-intensive process. Now, research performed in part at the National Institute of Standards and Technology (NIST) has revealed a way to reduce the energy demand in one key step of plastic manufacturing by using a class of materials that can filter impurities more efficiently than the conventional manufacturing process.

The findings, published in the journal Science, show that materials called metal-organic frameworks (MOFs) can effectively remove the contaminant acetylene from ethylene, the material from which much of the world’s plastic is made. The research suggests that filtering out acetylene using MOFs would produce ethylene at the high purity that industry demands while sidestepping the current need to convert acetylene to ethylene via a costly catalytic process.

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Neutrons probe structure of enzyme critical to development of next-generation HIV drugs

A team led by the Department of Energy’s Oak Ridge National Laboratory used neutron analysis to better understand a protein implicated in the replication of HIV, the retrovirus that causes AIDS. The enzyme, known as HIV-1 protease, is a key drug target for HIV and AIDS therapies.

Researchers from ORNL, Georgia State University and the Institut Laue-Langevin in France used neutron crystallography to uncover details of interactions of hydrogen bonds at the enzyme’s active site, revealing a pH-induced proton ‘hopping’ mechanism that guides its activity. The team discussed the findings in a paper published in the journal Angewandte Chemie.

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Neutrons tap into magnetism in topological insulators at high temperatures

A multi-institutional team of researchers has discovered novel magnetic behavior on the surface of a specialized material that holds promise for smaller, more efficient devices and other advanced technology. Researchers at the Department of Energy’s Oak Ridge National Laboratory, Massachusetts Institute of Technology and their collaborators used neutron scattering to reveal magnetic moments in hybrid topological insulator (TI) materials at room temperature, hundreds of degrees Fahrenheit warmer than the extreme sub-zero cold where the properties are expected to occur.

The discovery promises new opportunities for next-generation electronic and spintronic devices such as improved transistors and quantum computing technologies. Their research is discussed in a paper published in the journal Nature.


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Kitaev quantum spin liquid response in RuCl3

Researchers at the Department of Energy’s Oak Ridge National Laboratory used neutrons to uncover novel behavior in materials that holds promise for quantum computing. The findings, published in Nature Materials, provide evidence for long-sought phenomena in a two-dimensional magnet.

In 2006, the physicist Alexei Kitaev developed a theoretical model of microscopic magnets (“spins”) that interact in a fashion that leads to a disordered state called a quantum spin liquid. This “Kitaev quantum spin liquid” supports magnetic excitations equivalent to Majorana fermions—particles that are unusual in that they are their own antiparticles. The presence of Majorana fermions is of great interest because of their potential use as the basis for a qubit, the essential building block of quantum computers. Familiar magnetic materials exhibit magnetic excitations called “spin-waves” that occur in quantized lumps, but in the Kitaev quantum spin liquid, the lumps are split and the Majorana excitations are therefore termed “fractionalized.”

The form of magnetic excitations created in alpha-ruthenium trichloridewas found to be different from spin waves seen in ordinary magnets, but was very well-matched to the spectrum predicted for the Majorana fermions expected in the Kitaev quantum spin liquid.

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Broadening the Bilayer: Understanding New Theories in Organization in Cellular Membranes

Lipid molecules have split personalities—one part loves water, whereas the other avoids it at all costs. Lipids make up cell membranes, the frontline defense in preventing cellular access to bacterial and viral invaders. Many researchers believe that the membrane is not just a scaffold where proteins reside, but instead actually plays an important role in a number of biological processes. Researchers are also starting to see that lipids and proteins can form small patches, similar to a mosaic. This patchiness seems to have a functional role in the life of a cell and in regulating its different processes. Functional patches of lipids are commonly referred to as lipid rafts.

Neutrons offer guide to getting more out of solid-state lithium-ion batteries

Although they don’t currently have as much conductivity, solid-state electrolytes designed for lithium-ion batteries (LIBs) are emerging as a safer alternative to their more prevalent—sometimes flammable—liquid-electrolyte counterparts. A new study conducted at Oak Ridge National Laboratory’s Spallation Neutron Source (SNS), a Department of Energy Office of Science user facility, has revealed promising results that could drastically boost the performance of solid-state electrolytes, and could potentially lead to a safer, even more efficient battery.

Using neutron diffraction techniques via the VULCAN instrument, the team concluded an in-depth study probing the entire structure evolution of doped garnet-type electrolytes during the synthesis process to unravel the mechanism that boosts the lithium-ionic conductivity. Their findings were recently published in the journals Chemistry of Materials and the Journal of Materials Chemistry A.

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‘Repulsive’ quantum magnet

Neutron measurements at Oak Ridge National Laboratory’s Spallation Neutron Source are giving physicists new insight into the behavior of quantum magnets. A research team led by Young-June Kim from the University of Toronto used neutron spectroscopy to observe a novel type of energy band repulsion in a magnetic insulator. The study adds to scientists’ understanding of quasiparticles, a theoretical concept that describes many particle interactions inside a material.

This work was conducted at SEQUOIA, SNS beam line 17. The team’s results are published in Nature Physics.

NIST, UC Davis Scientists Float New Approach to Creating Computer Memory

What can skyrmions do for you? These ghostly quantum rings, heretofore glimpsed only under extreme laboratory conditions, just might be the basis for a new type of computer memory that never loses its grip on the data it stores. Now, thanks to a research team including scientists from the National Institute of Standards and Technology (NIST),* the exotic ring-shaped magnetic effects have been coaxed out of the physicist’s deepfreeze with a straightforward method that creates magnetic skyrmions under ambient room conditions. The achievement brings skyrmions a step closer for use in real-world data storage as well as other novel magnetic and electronic technologies.

It took a trip to NIST to confirm the skyrmions’ existence. Creating them involves placing arrays of tiny magnetized cobalt disks atop a thin film made of cobalt and palladium; the NIST Center for Neutron Research (NCNR) had just developed a state-of-art polarized neutron reflectometer that was well suited to study their lab results. Working with NCNR scientists, the team used neutrons to see through the disk to spot the skyrmions underneath. The team also captured images of the whirling configurations in the disk array at NIST’s Center for Nanoscale Science and Technology (CNST) and Lawrence Berkeley Laboratory. This work was published in Nature Communications.

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