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Report Sheds New Insights on the Spin Dynamics of a Material Candidate for Low-Power Devices

In a report published in Nano LettersArgonne researchers reveal new insights into the properties of a magnetic insulator that is a candidate for low-power device applications; their insights form early stepping-stones towards developing high-speed, low-power electronics that use electron spin rather than charge to carry information.

Researchers Find Computer Code That Volkswagen Used to Cheat Emissions Tests

An international team of researchers has uncovered the mechanism that allowed Volkswagen to circumvent U.S. and European emission tests over at least six years before the Environmental Protection Agency put the company on notice in 2015 for violating the Clean Air Act. During a year-long investigation, researchers found code that allowed a car's onboard computer to determine that the vehicle was undergoing an emissions test.

Physicists Discover That Lithium Oxide on Tokamak Walls Can Improve Plasma Performance

A team of physicists has found that a coating of lithium oxide on the inside of fusion machines known as tokamaks can absorb as much deuterium as pure lithium can.

Scientists Perform First Basic Physics Simulation of Spontaneous Transition of the Edge of Fusion Plasma to Crucial High-Confinement Mode

PPPL physicists have simulated the spontaneous transition of turbulence at the edge of a fusion plasma to the high-confinement mode that sustains fusion reactions. The research was achieved with the extreme-scale plasma turbulence code XGC developed at PPPL in collaboration with a nationwide team.

Green Fleet Technology

New research at Penn State addresses the impact delivery trucks have on the environment by providing green solutions that keep costs down without sacrificing efficiency.

Scientists Demonstrate New Real-Time Technique for Studying Ionic Liquids at Electrode Interfaces

This electron microscope-based imaging technique could help scientists optimize the performance of ionic liquids for batteries and other energy storage devices.

How Scientists Turned a Flag Into a Loudspeaker

A paper-thin, flexible device created at Michigan State University not only can generate energy from human motion, it can act as a loudspeaker and microphone as well, nanotechnology researchers report in the May 16 edition of Nature Communications.

Assembling Life's Molecular Motor

As part of a project dedicated to modeling how single-celled purple bacteria turn light into food, a team of computational scientists from the University of Illinois at Urbana-Champaign (UIUC) simulated a complete ATP synthase in all-atom detail. The work builds on the project's first phase--a 100-million atom photosynthetic organelle called a chromatophore--and gives scientists an unprecedented glimpse into a biological machine whose energy efficiency far surpasses that of any artificial system.

Engineering Researchers Apply Data Science to Better Predict Effect of Weather and Other Conditions on Solar Panels

In a new study, a team of researchers from Case Western Reserve University and Gebze Technical University (GTU) in Turkey used data science to determine and predict the effects of exposure to weather and other conditions on materials in solar panels.

More Natural Dust in the Air Improves Air Quality in Eastern China

Man-made pollution in eastern China's cities worsens when less dust blows in from the Gobi Desert, according to a new study. That's because dust plays an important role in determining the air temperatures and thereby promoting winds to blow away man-made pollution. Less dust means the air stagnates, with man-made pollution sticking around longer.


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Rensselaer Polytechnic Institute Graduates Urged to Embrace Change at 211th Commencement

Describing the dizzying pace of technological innovation, former United States Secretary of Energy Ernest J. Moniz urged graduates to "anticipate career change, welcome it, and manage it to your and your society's benefit" at the 211th Commencement at Rensselaer Polytechnic Institute (RPI) Saturday.

ORNL Welcomes Innovation Crossroads Entrepreneurial Research Fellows

Oak Ridge National Laboratory today welcomed the first cohort of innovators to join Innovation Crossroads, the Southeast region's first entrepreneurial research and development program based at a U.S. Department of Energy national laboratory.

Department of Energy Secretary Recognizes Argonne Scientists' Work to Fight Ebola, Cancer

Two groups of researchers at Argonne earned special awards from the office of the U.S. Secretary of Energy for addressing the global health challenges of Ebola and cancer.

Jefferson Science Associates, LLC Recognized for Leadership in Small Business Utilization

Jefferson Lab/Jefferson Science Associates has a long-standing commitment to doing business with and mentoring small businesses. That commitment and support received national recognition at the 16th Annual Dept. of Energy Small Business Forum and Expo held May 16-18, 2017 in Kansas City, Mo.

Rensselaer Polytechnic Institute President's Commencement Colloquy to Address "Criticality, Incisiveness, Creativity"

To kick off the Rensselaer Polytechnic Institute Commencement weekend, the annual President's Commencement Colloquy will take place on Friday, May 19, beginning at 3:30 p.m. The discussion, titled "Criticality, Incisiveness, Creativity," will include the Honorable Ernest J. Moniz, former Secretary of Energy, and the Honorable Roger W. Ferguson Jr., President and CEO of TIAA, and will be moderated by Rensselaer President Shirley Ann Jackson.

ORNL, University of Tennessee Launch New Doctoral Program in Data Science

The Tennessee Higher Education Commission has approved a new doctoral program in data science and engineering as part of the Bredesen Center for Interdisciplinary Research and Graduate Education.

SurfTec Receives $1.2 Million Energy Award to Develop Novel Coating

The Department of Energy has awarded $1.2 million to SurfTec LLC, a company affiliated with the U of A Technology Development Foundation, to continue developing a nanoparticle-based coating to replace lead-based journal bearings in the next generation of electric machines.

Ames Laboratory Scientist Inducted Into National Inventors Hall of Fame

Iver Anderson, senior metallurgist at Ames Laboratory, has been inducted into the National Inventors Hall of Fame.

DOE HPC4Mfg Program Funds 13 New Projects to Improve U.S. Energy Technologies Through High Performance Computing

A U.S. Department of Energy (DOE) program designed to spur the use of high performance supercomputers to advance U.S. manufacturing is funding 13 new industry projects for a total of $3.9 million.

Penn State Wind Energy Club Breezes to Victory in Collegiate Wind Competition

The Penn State Wind Energy Club breezed through the field at the U.S. Department of Energy Collegiate Wind Competition 2017 Technical Challenge, held April 20-22 at the National Wind Technology Center near Boulder, Colorado--earning its third overall victory in four years at the Collegiate Wind Competition.


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Casting a Wide Net

Designed molecules will provide positive impacts in energy production by selectively removing unwanted ions from complex solutions.

New Software Tools Streamline DNA Sequence Design-and-Build Process

Enhanced software tools will accelerate gene discovery and characterization, vital for new forms of fuel production.

The Ultrafast Interplay Between Molecules and Materials

Computer calculations by the Center for Solar Fuels, an Energy Frontier Research Center, shed light on nebulous interactions in semiconductors relevant to dye-sensitized solar cells.

Supercapacitors: WOODn't That Be Nice

Researchers at Nanostructures for Electrical Energy Storage, an Energy Frontier Research Center, take advantage of nature-made materials and structure for energy storage research.

Groundwater Flow Is Key for Modeling the Global Water Cycle

Water table depth and groundwater flow are vital to understanding the amount of water that plants transmit to the atmosphere.

Finding the Correct Path

A new computational technique greatly simplifies the complex reaction networks common to catalysis and combustion fields.

Opening Efficient Routes to Everyday Plastics

A new material from the Inorganometallic Catalyst Design Center, an Energy Frontier Research Center, facilitates the production of key industrial supplies.

Fight to the Top: Silver and Gold Compete for the Surface of a Bimetallic Solid

It's the classic plot of a buddy movie. Two struggling bodies team up to drive the plot and do good together. That same idea, when it comes to metals, could help scientists solve a big problem: the amount of energy consumed by making chemicals.

Saving Energy Through Light Control

New materials, designed by researchers at the Center for Excitonics, an Energy Frontier Research Center, can reduce energy consumption with the flip of a switch.

Teaching Perovskites to Swim

Scientists at the ANSER Energy Frontier Research Center designed a two-component layer protects a sunlight-harvesting device from water and heat.


How X-Rays Pushed Topological Matter R&D Over the Top

Article ID: 673039

Released: 2017-04-17 08:00:51

Source Newsroom: Lawrence Berkeley National Laboratory

  • Credit: Yulin Chen, Z.-X. Shen/Stanford University

    A 3-D image of the surface band structure of bismuth telluride.

  • Credit: Roy Kaltschmidt/Berkeley Lab

    Beamline 10.0.1 at Berkeley Lab’s Advanced Light Source is optimized for studies of topological properties in materials.

  • Credit: David Hsieh, Yuqi Xia, Andrew Wray/Princeton University

    Band structure of bismuth selenide, a topological insulator. The red areas represent surface states and the vertical space between the yellow areas is the bulk band gap. At lower right, a 3-D schematic of the cone-shaped surface band structure. The spin states (yellow arrows) indicate that electrons on the surface won’t backscatter from disorder and impurities in the material.

  • Credit: Roy Kaltschmidt/Berkeley Lab

    Alexei Fedorov, a staff scientist at Berkeley Lab's Advanced Light Source, is pictured here at Beamline 12.0.1, which is specialized for topological matter research.

While using X-rays generated by the Advanced Light Source (ALS), a synchrotron facility at the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab), to study a bismuth-containing thermoelectric material that can convert heat into electricity, physicist M. Zahid Hasan of Princeton University saw that something was interfering with the anticipated view of electrons’ behavior inside the material.

Knowing how electrons move within this material was sought as a key to decipher how it worked, so this interference -- which he and his team observed more than a decade ago during an experiment employing an X-ray-based technique dubbed ARPES (angle-resolved photoemission spectroscopy) -- was a problem ... at first.

“Since 2004, I was involved with this research looking for a better understanding of bismuth-based thermoelectric materials, among other things,” said Hasan.

Around 2007, after completing more X-ray experiments at the ALS and other synchrotrons, and after gaining some understanding of the theory related to his team’s observations, it would become clear to Hasan that this obstruction was actually a discovery: One that would spark a revolution in materials research that continues today, and that could eventually lead to new generations of electronics and quantum technologies.

Topological matter research is now a flourishing field of research at the ALS, with several staff members devoted to supporting X-ray techniques that largely focus on the properties of topological matter.

“Since 2005, something on the surface was annoying me quite a bit,” said Hasan, a Princeton physics professor who in late 2016 became a visiting faculty member at Berkeley Lab’s Materials Sciences Division and a Visiting Miller Professor at UC Berkeley. “I could not get rid of the surface states.”

Back at Princeton, Hasan struck up a conversation with a fellow physics professor, Duncan Haldane, and he also spoke with Charles Kane, a physics professor at the neighboring University of Pennsylvania, for their collective theoretical insight about the surface effects he was seeing in some bismuth-containing materials. “At that point I was not aware of the theoretical predictions.”

They discussed theoretical work, some of it dating back several decades, that had explored bizarre and resilient “topological” states in which electrons could move about the surface of a thin material with next to no resistance -- like in a traditional superconductor but with a different mechanism.

The theoretical work provided little clue in how to find the effects in the materials exhibiting this phenomenon, though. So Hasan set out on a path that crossed into the fields of quantum theory, particle physics, and complex mathematics.

“I had to translate all of the abstract math into these experiments,” he said. “It was like translating from a foreign language.”

Flash forward to October 2016, and this time Haldane was describing his early theoretical work during a Nobel Prize press conference. Haldane shared the 2016 Nobel Prize in Physics with David Thouless of the University of Washington (a former postdoctoral researcher at Berkeley Lab) and J. Michael Kosterlitz of Brown University for their work in “theoretical discoveries of topological phase transitions and topological phases of matter.” 

Haldane had said at the time of the Nobel Prize announcement, “I put in the first paper that this is unlikely to be anything anyone could make.” His work, he said, was a “sleeper” that “sat around as an interesting toy model for a very long time -- no one quite knew what to do with it.”

What helped bring that “toy model” to life were later theories by Kane and collaborators, and innovative ARPES studies at the ALS and other synchrotrons that directly probed exotic topological states in some materials.

Synchrotrons like the ALS have dozens of beamlines that produce focused X-rays and other types of light beams for a variety of experiments that explore the properties of exotic materials and other samples at tiny scales, and ARPES provides a window into materials’ electron properties.

The Nobel Committee, in its supporting materials for the prize, had cited early experiments by Hasan’s team at the ALS on materials exhibiting topological insulator phases. A topological insulator acts like an electrical conductor on the surface and an insulator (with no electrical flow) inside.

Zahid Hussain, division deputy at the ALS said, “Hasan is an exceptional scientist with a deep understanding of both theory and experiment. He is the reason this became experimentally visible. One experiment did that.”

Hasan’s work provided an early demonstration of a 3-D topological insulator, for example.

In these materials, the electron motion is relatively robust, and is immune to many types of impurities and deformities. Researchers have found examples of topological properties in materials even at room temperature.

This is a critical advantage over so-called high-temperature superconductors, which must be chilled to extreme temperatures in order to achieve a nearly resistance-free flow of electrons.

With topological materials, the electrons exhibit unique patterns in a property known as electron spin that is analogous to a compass needle pointing up or down, and this property can change based on the electron’s path and position in a material.

One potential future application for the spin properties of electrons in topological materials is spintronics, an emerging field that seeks to control the spin on demand to transmit and store information, much like the zeroes and ones in traditional computer memory.

Spin could also be harnessed as the information carriers in quantum computers, which could conceivably carry out exponentially more calculations of a certain type in a shorter time than conventional supercomputers.

Jonathan Denlinger, a staff scientist in the Scientific Support Group at the ALS, said the breakthrough studies on materials with topological behavior led to a rapid shift in focus on materials’ surface properties. Researchers had historically been more interested in electrons within the “bulk,” or inside of materials. 

Hasan’s group used three ALS beamlines -- MERLIN, 12.0.1, and 10.0.1 -- in pioneering ARPES studies of topological matter. Hasan was a co-leader on the proposal that led to the construction of MERLIN in the early 2000s.

Denlinger, and fellow ALS staff scientists Alexei Fedorov and Sung-Kwan Mo, work at these ALS beamlines, which specialize in ARPES and a related variant called spin-resolved photoelectron spectroscopy. The techniques can provide detailed information about how electrons travel in materials and also about the electrons’ spin orientation.

ARPES beamlines at the ALS remain in high demand for topological matter research. Fedorov said, “These days, almost every proposal submitted to our beamline in one way or another deals with topological matter.”

The quest for discoveries of new topological matter at the ALS will also be boosted by a beamline known as MAESTRO that started up last year. A new beamline called COSMIC (coherent scattering and microscopy), now in commissioning, will help in visualizing exotic ordered structures formed in some topological materials.

ALS-U, a planned upgrade of the ALS, should improve and enhance topological matter studies using the ALS,” Mo said. “It will allow us to focus down to a very small spot,” which could reveal more detail in the electron behavior of topological matter.

Improved X-ray performance could help identify some topological materials that were previously overlooked, and to better distinguish and classify their properties, Hasan said.

Hasan’s early work in topological matter, including topological insulators, led him to the detection of a previously theorized massless particle known as the Weyl fermion in topological semimetals, and he is now devising a related experiment that he hopes will mimic the period of the early universe in which particles began to take on mass.

Denlinger, Fedorov, and Mo are gearing up for more studies of topological matter, and are reaching out to possible collaborators across Berkeley Lab and the global scientific community.

Nanoscale materials show a lot of promise for topological materials applications, and thermoelectrics -- those same materials that can transfer heat to electricity and vice versa, and that led to the first realization of topological matter in X-ray experiments -- should see performance gains in the short term thanks to the feverish pace of R&D in the field, Fedorov noted.

Hasan, too, said he is excited about progress in the field. “We are in the middle of a topological revolution in physics, for sure,” he said.

The Advanced Light Source (ALS) is a DOE Office of Science User Facility. Operation of ALS and this work is supported by the DOE Office of Science.

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Lawrence Berkeley National Laboratory addresses the world’s most urgent scientific challenges by advancing sustainable energy, protecting human health, creating new materials, and revealing the origin and fate of the universe. Founded in 1931, Berkeley Lab’s scientific expertise has been recognized with 13 Nobel Prizes. The University of California manages Berkeley Lab for the U.S. Department of Energy’s Office of Science. For more, visit www.lbl.gov.

DOE’s 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 science.energy.gov.