From Brookhaven National Lab: “Lighting the Way to Centralized Computing Support for Photon Science”

From Brookhaven National Lab

December 18, 2018
Ariana Tantillo
atantillo@bnl.gov

Brookhaven Lab’s Computational Science Initiative hosted a workshop for scientists and information technology specialists to discuss best practices for managing and processing data generated at light source facilities

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On Sept. 24, scientists and information technology specialists from various labs in the United States and Europe participated in a full-day workshop—hosted by the Scientific Data and Computing Center at Brookhaven Lab—to share challenges and solutions to providing centralized computing support for photon science. From left to right, seated: Eric Lancon, Ian Collier, Kevin Casella, Jamal Irving, Tony Wong, and Abe Singer. Standing: Yee-Ting Li, Shigeki Misawa, Amedeo Perazzo, David Yu, Hironori Ito, Krishna Muriki, Alex Zaytsev, John DeStefano, Stuart Campbell, Martin Gasthuber, Andrew Richards, and Wei Yang.

Large particle accelerator–based facilities known as synchrotron light sources provide intense, highly focused photon beams in the infrared, visible, ultraviolet, and x-ray regions of the electromagnetic spectrum. The photons, or tiny bundles of light energy, can be used to probe the structure, chemical composition, and properties of a wide range of materials on the atomic scale. For example, scientists direct the brilliant light at batteries to resolve charge and discharge processes, at protein-drug complexes to understand how the molecules bind, and at soil samples to identify environmental contaminants.

As these facilities continue to become more advanced through upgrades to light sources, detectors, optics, and other technologies, they are producing data at a higher rate and with increasing complexity. These big data present a challenge to facility users, who have to be able to quickly analyze the data in real time to make sure their experiments are functioning as they should be. Once they have concluded their experiments, users also need ways to store, retrieve, and distribute the data for further analysis. High-performance computing hardware and software are critical to supporting such immediate analysis and post-acquisition requirements.

The U.S. Department of Energy’s (DOE) Brookhaven National Laboratory hosted a one-day workshop on Sept. 24 for information technology (IT) specialists and scientists from various labs around the world to discuss best practices and share experiences in providing centralized computing support to photon science. Many institutions provide limited computing resources (e.g., servers, disk/tape storage systems) within their respective light source facilities for data acquisition and a quick check and feedback on the quality of the collected data. Though these facilities have computing infrastructure (e.g., login access, network connectivity, data management software) to support usage, access to computing resources is often time-constrained because of the high number and frequency of experiments being conducted at any given time. For example, the Diamond Light Source in the United Kingdom hosts about 9,000 experiments in a single year. Because of the limited computing resources, extensive (or multiple attempts at) data reconstruction and analysis must typically be performed outside of the facilities. But centralized computing centers can provide the resources needed to manage and process data being generated by such experiments.

Continuing a legacy of computing support

Brookhaven Lab is home to the National Synchrotron Light Source II (NSLS-II) [see below], a DOE Office of Science User Facility, that began operating in 2014 and is 10,000 times brighter than the original NSLS. Currently, 28 beamlines are in operation or commissioning and one beamline is under construction, and there is space to accommodate an additional 30 beamlines. NSLS-II is expected to generate tens of petabytes of data (one petabyte is equivalent to a stack of CDs standing nearly 10,000 feet tall) per year in the next decade.

Brookhaven is also home to the Scientific Data and Computing Center (SDCC), part of the Computational Science Initiative (CSI). The centralized data storage, computing, and networking infrastructure that SDCC provides has historically supported the RHIC and ATLAS Computing Facility (RACF). This facility provides the necessary resources to store, process, analyze, and distribute experimental data from the Relativistic Heavy Ion Collider (RHIC)—another DOE Office of Science User Facility at Brookhaven—and the ATLAS detector at CERN’s Large Hadron Collider in Europe.

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The amount of data that need to be archived and retrieved from tape storage has significantly increased over the past decade, as seen in the above graph. “Hot” storage refers to storing data that are frequently accessed, while “cold” storage refers to storing data that are rarely used.

“Brookhaven has a long tradition of providing centralized computing support to the nuclear and high-energy physics communities,” said workshop organizer Tony Wong, deputy director of SDCC. “A standard approach for dealing with their computing requirements has been developed for more than 50 years. New and advanced photon science facilities such as NSLS-II have very different requirements, and therefore we need to reconsider our approach. The purpose of the workshop was to gain insights from labs with a proven track record of providing centralized computing support for photon science, and to apply those insights at SDCC and other centralized computing centers. There are a lot of research organizations around the world who are similar to Brookhaven in the sense that they have a long history in data-intensive nuclear and high-energy physics experiments and are now branching out to newer data-intensive areas, such as photon science.”

Nearly 30 scientists and IT specialists from several DOE national laboratories—Brookhaven, Argonne, Lawrence Berkeley, and SLAC—and research institutions in Europe, including the Diamond Light Source and Science and Technology Facilities Council in the United Kingdom and the PETRA III x-ray light source at the Deutsches Elektronen-Synchrotron (DESY) in Germany, participated in this first-of-its-kind workshop. They discussed common challenges in storing, archiving, retrieving, sharing, and analyzing photon science data, and techniques to overcome these challenges.

Meeting different computing requirements

One of the biggest differences in computing requirements between nuclear and high-energy physics and photon science is the speed with which the data must be analyzed upon collection.

“In nuclear and high-energy physics, the data-taking period spans weeks, months, or even years, and the data are analyzed at a later date,” said Wong. “But in photon science, experiments sometimes only last a few hours to a couple of days. When your time at a beamline is this limited, every second counts. Therefore, it is vitally important for the users to be able to immediately check their data as it is collected to ensure it is of value. It is through these data checks that scientists can confirm whether the detectors and instruments are working properly.”

Photon science also has unique networking requirements, both internally within the light sources and central computing centers, and externally across the internet and remote facilities. For example, in the past, scientists could load their experimental results onto portable storage devices such as removable drives. However, because of the proliferation of big data, this take-it-home approach is often not feasible. Instead, scientists are investigating cloud-based data storage and distribution technology. While the DOE-supported Energy Sciences Network (ESnet)—a DOE Office of Science User Facility stewarded by Lawrence Berkeley National Laboratory—provides high-bandwidth connections for national labs, universities, and research institutions to share their data, no such vehicle exists for private companies. Additionally, sending, storing, and accessing data over the internet can pose security concerns in cases where the data are proprietary or involve confidential information, such as corporate entities.

Even nonproprietary academic research requires that some security measures are in place to ensure that the appropriate personnel are accessing the computing resources and data. The workshop participants discussed authentication and authorization infrastructure and mechanisms to address these concerns.

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ESnet provides network connections across the world to enable sharing of big data for scientific discovery.

Identifying opportunities and challenges

According to Wong, the workshop raised both concern and optimism. Many of the world’s light sources will be undergoing upgrades between 2020 and 2025 that will increase today’s data collection rates by three to 10 times.

“If we are having trouble coping with data challenges today, even taking into account advancements in technology, we will continue to have problems in the future with respect to moving data from detectors to storage and performing real-time analysis on the data,” said Wong. “On the other hand, SDCC has extensive experience in providing software visualization, cloud computing, authentication and authorization, scalable disk storage, and other infrastructure for nuclear and high-energy physics research. This experience can be leveraged to tackle the unique challenges of managing and processing data for photon science.”

Going forward, SDCC will continue to engage with the larger community of IT experts in scientific computing through existing information-exchange forums, such as HEPiX. Established in 1991, HEPiX comprises more than 500 scientists and IT system administrators, engineers, and managers who meet twice a year to discuss scientific computing and data challenges in nuclear and high-energy physics. Recently, HEPiX has been extending these discussions to other scientific areas, with scientists and IT professionals from various light sources in attendance. Several of the Brookhaven workshop participants attended the recent HEPiX Autumn/Fall 2018 Workshop in Barcelona, Spain.

“The seeds have already been planted for interactions between the two communities,” said Wong. “It is our hope that the exchange of information will be mutually beneficial.”

With this knowledge sharing, SDCC hopes to expand the amount of support provided to NSLS-II, as well as the Center for Functional Nanomaterials (CFN)—another DOE Office of Science User Facility at Brookhaven. In fact, several scientists from NSLS-II and CFN attended the workshop, providing a comprehensive view of their computing needs.

“SDCC already supports these user facilities but we would like to make this support more encompassing,” said Wong. “For instance, we provide offline computing resources for post-data acquisition analysis but we are not yet providing a real-time data quality IT infrastructure. Events like this workshop are part of SDCC’s larger ongoing effort to provide adequate computing support to scientists, enabling them to carry out the world-class research that leads to scientific discoveries.”

See the full article here .


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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.
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From Brookhaven National Lab: “High-Caliber Research Launches NSLS-II Beamline into Operations”

From Brookhaven National Lab

August 2, 2018
Stephanie Kossman
skossman@bnl.gov

Pratt & Whitney conduct the first experiments at a new National Synchrotron Light Source II beamline.

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Bruce Ravel is the lead scientist at the Beamline for Materials Measurement (BMM), a new, state-of-the-art experimental station at NSLS-II. BMM was constructed and is operated by the National Institute of Standards and Technology (NIST).

A new experimental station (beamline) has begun operations at the National Synchrotron Light Source II (NSLS-II)—a U.S. Department of Energy (DOE) Office of Science User Facility at DOE’s Brookhaven National Laboratory. Called the Beamline for Materials Measurement (BMM), it offers scientists state-of-the-art technology for using a classic synchrotron technique: x-ray absorption spectroscopy.

“There are critical questions in all areas of science that can be solved using x-ray absorption spectroscopy, from energy sciences and catalysis to geochemistry and materials science,” said Bruce Ravel, a physicist at the National Institute of Standards and Technology (NIST), which constructed and operates BMM through a partnership with NSLS-II.

X-ray absorption spectroscopy is a research technique that was developed in the 1980s and, since then, has been at the forefront of scientific discovery.

“The reason we’ve used this technique for 40 years and the reason why NIST built the BMM beamline is because it adds a great value to the scientific community,” Ravel explained.

The first group of researchers to conduct experiments at BMM came from jet engine manufacturer Pratt & Whitney. Senior Engineer Chris Pelliccione and colleagues used BMM to study the chemistry of jet engines.

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Pratt & Whitney Senior Engineer Chris Pelliccione (left) with NIST’s Bruce Ravel (right) at BMM’s workstation.

“We investigated the ceramic thermal barrier coatings used in jet engines,” Pelliccione said. “Due to the extreme temperature and pressure that these components operate in, the data from this investigation will help us design for durability. Our experiment at BMM was designed to understand some of the chemical interactions in more detail for today’s programs as well as tomorrow’s new breakthroughs.”

Coupling BMM’s advanced design with NSLS-II’s ultra-bright x-ray light, the scientists at Pratt & Whitney were able to determine the spatial distribution of chemical interactions in the coating.

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The Beamline for Materials Measurement (BMM) at the National Synchrotron Light Source II.

“We needed a beamline with a small focused beam size and high flux to obtain the quality of data we were interested in,” Pelliccione said. “BMM offers both of these capabilities and our measurements were very successful. We were able to extract valuable information about the coatings that is not easily accessible through other research techniques.”

Pratt & Whitney conducted its experiments at BMM during the final “commissioning” stage of the beamline, and the high-caliber research launched BMM into general operations.

“We hope to take advantage of the fantastic beamlines that are already up and running at NSLS-II, as well as those that are coming online soon,” Pelliccione concluded.

Ravel added, “It was incredibly gratifying to send Pratt & Whitney home with such valuable data. It is a very important part of NIST’s mission to work with companies and to promote U.S. innovation and industrial competitiveness.”

More about NIST and NSLS-II

NSLS-II is one of the world’s newest and most advanced synchrotron light sources. NSLS-II currently has 26 beamlines in operations and three in commissioning and construction phases. The facility has space for an additional 30 beamlines to be constructed. With the goal of “seeing” detailed views of chemical reactions, NSLS-II partnered with NIST to develop and operate three beamlines—SST-1, SST -2 and BMM—at NSLS-II.

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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.
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From University of Chicago: “UChicago scientists build trap to make tiny packages of light ‘collide’”

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University of Chicago

March 27, 2018
Louise Lerner

Study examines how to manipulate photons for quantum engineering.

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Asst. Prof. Jonathan Simon with the photon collider—the blue light is reflected by a precisely arranged set of mirrors to manipulate individual photons so that they ‘collide’ with one another. Photo by Jean Lachat.

The universe is illuminated via photons, the tiny individual particles that make up light, but they don’t interact with each other. To make them see the light, a team of University of Chicago physicists built a trap to help photons bounce off each other.

Their photon collider, described in the March 19 edition of Nature Physics, is the latest effort to make photons behave like other particles such as electrons—a step toward greater understanding and control of quantum systems, which may one day manifest as technology with new properties.

Quantum systems behave according to the strange laws that govern the smallest particles in the universe, like electrons. Scientists are increasingly interested in exploring new ways to harness the particles’ odd behaviors, like being in two states at once, and then choosing one only when measured.

Jonathan Simon, the Neubauer Family Assistant Professor of Physics and the James Franck Institute, is interested in how walls dividing matter and light begin to break down at this scale. Most electronic systems use electrons as the moving parts, but photons can display quantum properties just as easily as electrons—and photons’ quirks could both offer advantages as technologies and serve as models to understand the more slippery electrons. So his team wants to manipulate and stack photons to build matter out of light.

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(From left): Asst. Prof. Jonathan Simon, graduate student Ningyuan Jia and postdoctoral scholar Logan Clark with the photon collider. (Photo by Jean Lachat).

“Essentially we want to make photon systems into a kind of quantum Legos—blown-up materials that you can more easily study and tease out basic quantum design principles,” said Simon, who is also a fellow of the Institute for Molecular Engineering.

But because photons have no mass, no charge and no chill—they always want to travel at the speed of light—making them behave like other particles takes some delicate finagling.

Two years ago, Simon’s lab figured out a way to make photons behave as though they were in a magnetic field. The next challenge was to make photons react to each others’ presence, which light normally doesn’t.

In their lab, the scientists shine a weak laser to send a photon into a trap: a series of mirrors that keep it continuously bouncing around inside. The photon interacts with a cloud of rubidium atoms that are prepared so that once any atom in the cloud absorbs a photon, no other atom can. This repels other incoming photons behind them—as though they were “colliding.”

This offers a new way to understand some of the more poorly understood quantum properties, like entanglement—the state in which two particles become linked and share the same state even at great distances.

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Scientists use a weak laser to send a photon into a series of mirrors, which keeps the photon continuously bouncing around inside. (Photo by Jean Lachat).

“We don’t have much intuition about what kinds of entanglement lead to which properties,” Simon said, “so if we can understand an analogous system, that could give us some insight.”

There’s also interest in using photon systems for ultra-secure communications and to make computers. The team’s next step, Simon said, is to combine this setup with their previous one, to produce a set of photons that both interact with each other and with magnetic fields.

The first author on the study was UChicago graduate student Ningyuan Jia. Other co-authors were graduate students Albert Ryou (now at the University of Washington), Nathan Schine and Alexandros Georgakopoulos, as well as postdoctoral scholars Ariel Sommer (now at Lehigh University) and Logan Clark.

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From FNAL: “Photons continue to enlighten physicists”

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FNAL Art Image by Angela Gonzales

Fermilab is an enduring source of strength for the US contribution to scientific research world wide.

December 13, 2017
Andy Beretvas
Alessandra Lucà

You may be familiar with particles of light, called photons. Physicists give the name “prompt photons” to those that are produced by two particles smashing together — hard collisions — as contrasted with those resulting from the decay of other particles. The Tevatron produced prompt photons by the hard collisions between protons and antiprotons.

Knowing the likelihood that proton-antiproton collisions will produce prompt photons tells us something about the proton’s components, which are called quarks and gluons. In particular, we can learn about the density of quarks and gluons inside the colliding protons and get a better grasp on how they fragment into photons. These ingredients are all described in a theory called perturbative quantum chromodynamics.

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The cross section is presented as a function of the transverse energy of the photon.

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This plot compares three models — Pythia 6.216, Sherpa 1.4.1 and MCFM 6.8 — to the data.

Prompt photons at hadron colliders constitute an important test of perturbative quantum chromodynamics (pQCD), and may also be found in signatures of new physics processes. A precise measurement of prompt photon production is important to probe theoretical models, as well as to gain a better understanding of final states that contain energetic photons.

CDF physicists used the full Tevatron Run II data set, which contained 2.1 million collision events in the selected sample, to measure the prompt photons’ energies.

FNAL/Tevatron CDF detector

The researchers were particularly interested in the energy they carried in a direction perpendicular to the colliding beams, a property called transverse energy.

The photons’ transverse energy tells you something about the process that produced it. Photons with less than 100 GeV of transverse energy were generated primarily by quarks and gluons scattering off each other. At higher energies, the dominant process was the annihilation of a quark with its antimatter counterpart.

CDF conducted a similar study to this one in 2009. An important part of the measurement is that the photons should be isolated (the energy deposited near the photon is small). This time, a larger data set meant scientists could study a larger range of transverse photon energy, from 30 to 500 GeV. Moreover, a different statistical technique has been developed to better identify prompt photons; their identification is very challenging because of the huge background coming from other particles (mostly hadrons).

The results are presented in the first figure: The likelihood of proton-antiproton collisions producing a prompt photon decreases with increasing transverse energy. Note the data covers six orders of magnitude. This provides a challenge for theorists to come up with models that predicts this behavior correctly over so large a range.

Over the full range, data shows good agreement with the MCFM prediction. This model is a next-to-leading order pQCD calculation developed by Fermilab physicists John Campbell, Keith Ellis, Walter Giele and Ciaran Williams.

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From Stanford: “Eureka moment leads to new method of studying environmental toxins”

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March 31, 2016 [Stanford just saw fit to put this in social media.]
Ker Than

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View of the TVA Kingston Fossil Plant fly ash spill. Work using X-ray beams is clarifying how pollutants bind or release from solid surfaces and move into groundwater. Photo: Brian Stansberry via Wikimedia Commons

A technique for probing the surface of particles revealed how toxins move from the soil to groundwater.

In 1986, Gordon Brown used SLAC’s Stanford Synchrotron Radiation Lightsource (SSRL) to visualize something no one had ever seen before: the exact way that atoms bond to a solid surface.

SLAC/SSRL
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The work stemmed from a eureka moment that Brown had during the doctoral defense of graduate student Kim Hayes but has since grown into one of the seminal works in inorganic geochemistry, and even spawned a new field of study — molecular environmental science.

Knowing how charged ions interact with solid surfaces is crucial for understanding how toxic metal ions such as lead, arsenic and mercury or radioactive elements such as uranium may be released from particles in soils and sediments and into groundwater or vice versa. Using the techniques Brown’s team helped pioneer, scientists today can paint exquisitely detailed pictures of how metal ions bind to different solid surfaces, including those on nanoparticles.

“You can determine what other atoms are around the pollutant ions of interest, the inter-atomic distances separating them and the number and types of chemical bonds that keep them bound to the surface,” says Brown, a professor of geological sciences and of photon science. “This is crucial for understanding how easily they move from one place to another.”


Access mp4 video here .

Synchrotron-generated X-rays like those produced at SSRL are ideal for this type of investigation for a number of reasons, says John Bargar, a senior scientist at SLAC and Brown’s former PhD student. For one thing, synchrotron X-rays are highly focused, much like laser beams. “All of the photons produced are condensed into either a pencil beam or a narrow fan,” Bargar says. “That means you can use nearly all of the photons that you’re making with very little waste.”

Another advantage of synchrotron X-rays, Brown says, is that their extremely high intensity makes it possible to detect and study pollutant ions at the very low concentration levels typically found in many polluted environmental samples.

Moreover, synchrotron X-rays are polarized, meaning their waves vibrate primarily in a single plane. By modifying the direction of polarization, scientists can create very powerful probes for studying chemical bonds in molecules.

“A metal ion sitting inside a larger molecule is surrounded by many bonds. Oftentimes, we don’t want to interrogate all of those bonds at once,” Bargar says. “With polarized X-rays, we can selectively interrogate the bonds in a specific orientation.”

Recently, Brown and Bargar have collaborated to study how organic matter and live microbial organisms affect the binding affinities of different environmental pollutants to solid surfaces. Bargar and Brown are also investigating ways to harness bacterial aggregations called biofilms to neutralize the effects of environmental pollutants. In addition, they are also using synchrotron X-rays at SSRL to look for more efficient ways of safely extracting oil and gas from tight shales via hydraulic fracturing, a process that is transforming the energy landscape of the United States.

“The X-ray beams synchrotrons are able to generate today are about 15 orders of magnitude brighter than what was available when I was a graduate student. This has led to a revolution in all areas of science and engineering,” Brown says. “I could collect the data for my entire PhD thesis in one morning at SSRL now.”

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From MIT: “Electrons corralled using new quantum tool”


MIT News

May 7, 2015
David L. Chandler

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Image: Jon Wyrick/NIST

“Whispering gallery” effect confines electrons, could provide basis for new electron-optics devices.

Researchers have succeeded in creating a new “whispering gallery” effect for electrons in a sheet of graphene — making it possible to precisely control a region that reflects electrons within the material. They say the accomplishment could provide a basic building block for new kinds of electronic lenses, as well as quantum-based devices that combine electronics and optics.

The new system uses a needle-like probe that forms the basis of present-day scanning tunneling microscopes (STM), enabling control of both the location and the size of the reflecting region within graphene — a two-dimensional form of carbon that is just one atom thick.

The new finding is described in a paper appearing in the journal Science, co-authored by MIT professor of physics Leonid Levitov and researchers at the National Institute of Standards and Technology (NIST), the University of Maryland, Imperial College London, and the National Institute for Materials Science (NIMS) in Tsukuba, Japan.

When the sharp tip of the STM is poised over a sheet of graphene, it produces a circular barrier on the sheet that “acts as a perfect curved mirror” for electrons, Levitov says, reflecting them along the curved surface until they begin to interfere with themselves. This controllable reflectivity and interference is similar, he adds, to so-called “whispering gallery” confinement modes that have been used in optical and acoustic systems — but these have not been tunable or adjustable.

“In optics, whispering gallery resonators are known and useful,” Levitov says. “They provide high-quality cavities that find applications in sensing, spectroscopy, and communications. But the usual problem in optics is they’re not tunable.” Similarly, previous attempts to create quantum “corrals” for electrons have used atoms precisely positioned on a surface, which cannot be reconfigured easily.

The confinement in this case is produced by the boundary between two different regions on the graphene surface, corresponding to the “p” and “n” regions in a transistor. In this case, a circular region just beneath the STM tip takes on one polarity, and the surrounding region the opposite polarity, creating a controllable circular junction between the two regions. Electrons inside sheets of graphene behave like particles of light; in this case, the circular junction acts as a curved mirror that can focus and control the electrons.

It’s too early to predict what specific uses might be found for this phenomenon, Levitov says, but adds, “Any resonator can be used for a variety of things.”

This electron resonator combines several good features. There’s clearly something special about having tunability and also high quality at the same time.”

Philip Kim, a professor of physics at Harvard University who was not connected with this research, says it is “a very notable example of demonstrating novel electronic properties of graphene.” He adds, “Electrons in graphene behave like photons confined in a two-dimensional atomic sheet. This work unambiguously demonstrates that electrons confined in the potential created by scanning probe microscope exhibit a wave like resonance behavior, known as whispering gallery mode.”

Because the new system is based on well-established STM technology, it could be developed relatively quickly into usable devices, Levitov suggests. And conveniently, the STM not only creates the whispering gallery effect, but also provides a means of observing the results, to study the phenomenon. “The tip does double-duty in this case,” he says.

This could be a step toward the creation of electronic lenses, Levitov says — “a concept that intrigues graphene researchers.” In principle, these could provide a way of observing objects one-thousandth the size of those visible using light waves.

Electronic lenses would represent a fundamentally different approach from existing electron microscopes, which bombard a surface with high-energy beams of electrons, obliterating any subtle effects within the objects being observed. Electron lenses, by contrast, would be able to observe the ambient low-energy electrons within the object itself.

An appealing feature of the setup developed in NIST is that the boundary between the two surface regions, which can serve as a lens, is movable, since it is carried along with the STM tip when it is scanning the surface. This could make it possible to study “subtle things about how charge carriers behave at a microscopic level, that you can’t see from the outside,” Levitov says.

The new work by Levitov and his colleagues provides one piece of such a system — and potentially of other advanced electro-optical systems, he says, such as negative-refraction materials that have been proposed as a kind of “invisibility cloak.” The new whispering-gallery mode for electrons is part of a toolbox that could lead to a whole family of new quantum-based electron-optics devices. It could also be used for high-fidelity sensing, since such resonators “can be used to enhance your sensitivity to very small signals,” Levitov says.

Harvard’s Kim says that this work “is an important step toward building novel electronic applications, based on the unique relativistic quantum-mechanical behavior of electrons in graphene.”

The research team also included graduate student Joaquin Rodriguez-Nieva from MIT; Yue Zhao, Jonathan Wyrick, Fabian Natterer, Nikolai Zhitenev, and Joseph Stroscio from NIST; Cyprian Lewandowski from Imperial College London; and Kenji Watanabe and Takashi Taniguchi from NIMS.

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From BNL: “Physicists Solve Low-Temperature Magnetic Mystery”

Brookhaven Lab

March 27, 2015
Chelsea Whyte, (631) 344-8671 or Peter Genzer, (631) 344-3174

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Ignace Jarrige shown with the sample used in the experiment.

Researchers have made an experimental breakthrough in explaining a rare property of an exotic magnetic material, potentially opening a path to a host of new technologies. From information storage to magnetic refrigeration, many of tomorrow’s most promising innovations rely on sophisticated magnetic materials, and this discovery opens the door to harnessing the physics that governs those materials.

The work, led by Brookhaven National Laboratory physicist Ignace Jarrige, and University of Connecticut professor Jason Hancock, together with collaborators from Japan and Argonne National Laboratory, marks a major advance in the search for practical materials that will enable several types of next-generation technology. A paper describing the team’s results was published this week in the journal Physical Review Letters.

The work is related to the Kondo Effect, a physical phenomenon that explains how magnetic impurities affect the electrical resistance of materials. The researchers were looking at a material called ytterbium-indium-copper-four (usually written using its chemical formula: YbInCu4).

YbInCu4 has long been known to undergo a unique transition as a result of changing temperature. Below a certain temperature, the material’s magnetism disappears, while above that temperature, it is strongly magnetic. This transition, which has puzzled physicists for decades, has recently revealed its secret. “We detected a gap in the electronic spectrum, similar to that found in semiconductors like silicon, whose energy shift at the transition causes the Kondo Effect to strengthen sharply,” said Jarrige

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From Left to Right: Jason Hancock, Diego Casa, and Jung-ho Kim, shown with one of the instruments used in the experiment.

Electronic energy gaps define how electrons move (or don’t move) within the material, and are the critical component in understanding the electrical and magnetic properties of materials. “Our discovery goes to show that tailored semiconductor gaps can be used as a convenient knob to finely control the Kondo Effect and hence magnetism in technological materials,” said Jarrige.

To uncover the energy gap, the team used a process called Resonant Inelastic X-Ray Scattering (RIXS), a new experimental technique that is made possible by an intense X-ray beam produced at a synchrotron operated by the Department of Energy and located at Argonne National Laboratory outside of Chicago. By placing materials in the focused X-ray beam and sensitively measuring and analyzing how the X-rays are scattered, the team was able to uncover elusive properties such as the energy gap and connect them to the enigmatic magnetic behavior.

The new physics identified through this work suggest a roadmap to the development of materials with strong “magnetocaloric” properties, the tendency of a material to change temperature in the presence of a magnetic field. “The Kondo Effect in YbInCu4 turns on at a very low temperature of 42 Kelvin (-384F),” said Hancock, “but we now understand why it happens, which suggests that it could happen in other materials near room temperature.” If that material is discovered, according to Hancock, it would revolutionize cooling technology.

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During the RIXS experiment, an X-ray beam is used to excite electrons inside the sample. The X-ray loses energy during the process and then is scattered out of the sample. A fine analysis of the scattered X-rays yields insight into the mechanism that controls the strength of the Kondo Effect.

Household use of air conditioners in the US accounts for over $11 billion in energy costs and releases 100 million tons of carbon dioxide annually. Use of the magnetocaloric effect for magnetic refrigeration as an alternative to the mechanical fans and pumps in widespread use today could significantly reduce those numbers.

In addition to its potential applications to technology, the work has advanced the state of the art in research. “The RIXS technique we have developed can be applied in other areas of basic energy science,” said Hancock, noting that the development is very timely, and that it may be useful in the search for “topological Kondo insulators,” materials which have been predicted in theory, but have yet to be discovered.

See the full article here.

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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.
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