From Berkeley Lab: “Surprising Control over Photoelectrons from a Topological Insulator”

Berkeley Lab

Berkeley Lab scientists discover how a photon beam can flip the spin polarization of electrons emitted from an exciting new material

“Plain-looking but inherently strange crystalline materials called 3D topological insulators (TIs) are all the rage in materials science. Even at room temperature, a single chunk of TI is a good insulator in the bulk, yet behaves like a metal on its surface.

The interior bulk of a topological insulator is indeed an insulator, but electrons (spheres) move swiftly on the surface as if through a metal. They are spin-polarized, however, with their momenta (directional ribbons) and spins (arrows) locked together. Berkeley Lab researchers have discovered that the spin polarization of photoelectrons (arrowed sphere at upper right) emitted when the material is struck with high-energy photons (blue-green waves from left) is completely determined by the polarization of this incident light. (Image Chris Jozwiak, Zina Deretsky, and Berkeley Lab Creative Services Office)

Researchers find TIs exciting partly because the electrons that flow swiftly across their surfaces are ‘spin polarized’: the electron’s spin is locked to its momentum, perpendicular to the direction of travel. These interesting electronic states promise many uses – some exotic, like observing never-before-seen fundamental particles, but many practical, including building more versatile and efficient high-tech gadgets, or, further into the future, platforms for quantum computing.

A team of researchers from the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) and the University of California at Berkeley has just widened the vista of possibilities with an unexpected discovery about TIs: when hit with a laser beam, the spin polarization of the electrons they emit (in a process called photoemission) can be completely controlled in three dimensions, simply by tuning the polarization of the incident light.

‘The first time I saw this it was a shock; it was such a large effect and was counter to what most researchers had assumed about photoemission from topological insulators, or any other material,’ says Chris Jozwiak of Berkeley Lab’s Advanced Light Source (ALS), who worked on the experiment. ‘Being able to control the interaction of polarized light and photoelectron spin opens a playground of possibilities.’”

See the full article here.

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From Berkeley Lab: “Long Predicted Atomic Collapse State Observed in Graphene”

Berkeley Lab

Berkeley Lab researchers recreate elusive phenomenon with artificial nuclei

March 07, 2013
Lynn Yarris

“The first experimental observation of a quantum mechanical phenomenon that was predicted nearly 70 years ago holds important implications for the future of graphene-based electronic devices. Working with microscopic artificial atomic nuclei fabricated on graphene, a collaboration of researchers led by scientists with the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) and the University of California (UC) Berkeley have imaged the “atomic collapse” states theorized to occur around super-large atomic nuclei.

An artificial atomic nucleus made up of five charged calcium dimers is centered in an atomic-collapse electron cloud. (Image courtesy of Michael Crommie)

‘Atomic collapse is one of the holy grails of graphene research, as well as a holy grail of atomic and nuclear physics,’ says Michael Crommie, a physicist who holds joint appointments with Berkeley Lab’s Materials Sciences Division and UC Berkeley’s Physics Department. ‘While this work represents a very nice confirmation of basic relativistic quantum mechanics predictions made many decades ago, it is also highly relevant for future nanoscale devices where electrical charge is concentrated into very small areas.’”

Michael Crommie is a physicist who holds joint appointments with Berkeley Lab’s Materials Sciences Division and UC Berkeley’s Physics Department. (Photo by Roy Kaltschmidt)

See the full article here.

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From Berkeley Lab: “In the Blink of an Eye: X-ray Imaging on the Attosecond Timescale”

Berkeley Lab

March 07, 2013
Lynn Yarris

“In the blink of an eye, more attoseconds have expired than the age of Earth measured in – minutes. A lot more. To be precise, an attosecond is one billionth of a billionth of a second. The attosecond timescale is where you must go to study the electron action that is the starting point of all of chemistry. Not surprisingly, chemists are most eager to explore it with X-rays, the region of the electromagnetic spectrum that can probe the core electrons of atoms, the electrons that uniquely identify atomic species.

Berkeley Lab’s Ali Belkacem

Ali Belkacem, a chemist with the Lawrence Berkeley National Laboratory, has been using powerful laboratory-scale lasers to test whether multidimensional nonlinear x-ray spectroscopy on the attosecond timescale is practical for the light sources of the future – and just what combination of beam characteristics is needed to define them.

Heralded as the science of the 21st century by Science and The Economist, attosecond science is a new frontier of molecular and material science. It is expected to catalyze novel applications in a wide range of fields such as nanotechnology and life sciences, based on the ultimate visualization and control of the quantum nature of the electron.”

See the full article here.

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From Berkeley Lab: “Searching for the Solar System’s Chemical Recipe”

Berkeley Lab

Berkeley Lab’s Chemical Dynamics Beamline points to why isotope ratios in interplanetary dust and meteorites differ from Earth’s

February 20, 2013
Paul Preuss

“By studying the origins of different isotope ratios among the elements that make up today’s smorgasbord of planets, moons, comets, asteroids, and interplanetary ice and dust, Mark Thiemens and his colleagues hope to learn how our solar system evolved. Thiemens, Dean of the Division of Physical Sciences at the University of California, San Diego, has worked on this problem for over three decades.

The protosun evolved in a hot nebula of infalling gas and dust that formed an accretion disk (green) of surrounding matter. Visible and ultraviolet light poured from the sun, irradiating abundant clouds of carbon monoxide, hydrogen sulfide, and other chemicals. Temperatures near the sun were hot enough to melt silicates and other minerals, forming the chondrules found in early meteoroids (dashed black circles). Beyond the “snowline” (dashed white curves), water, methane, and other compounds condensed to ice. Numerous chemical reactions contributed to the isotopic ratios seen in relics of the early solar system today.

In recent years his team has found the Chemical Dynamics Beamline of the Advanced Light Source (ALS) at the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) to be an invaluable tool for examining how photochemistry determines the basic ingredients in the solar system recipe.

‘Mark and his colleagues Subrata Chakraborty and Teresa Jackson wanted to know if photochemistry could explain some of the differences in isotope ratios between Earth and what’s found in meteorites and interplanetary dust particles,’ says Musahid (Musa) Ahmed of Berkeley Lab’s Chemical Sciences Division, a scientist at the Chemical Dynamics Beamline who works with the UC San Diego team. ‘They needed a source of ultraviolet light powerful enough to dissociate gas molecules like carbon monoxide, hydrogen sulfide, and nitrogen. That’s us: our beamline basically provides information about gas-phase photodynamics.’”

At this point, I direct you to the full article. There is a lot going on here.

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From Berkeley Lab: “Engineering Bacterial Live Wires”

Berkeley Lab

February 28, 2013
Lita Stephenson

Just like electronics, living cells use electrons for energy and information transfer. Despite electrons being a common ‘language’ of the living and electronic worlds, living cells cannot speak to our largely technological realm. Cell membranes are largely to blame for this inability to plug cells into our computers: they form a greasy barrier that tightly controls charge balance in a cell. Thus, giving a cell the ability to communicate directly with an electrode would lead to enormous opportunities in the development of new energy conversion techniques, fuel production, biological reporters, or new forms of bioelectronic systems.

Previous studies performed by scientists and collaborators at Lawrence Berkeley National Laboratory’s (Berkeley Lab) Molecular Foundry have made enormous headway toward cellular-electrode communication by using E. coli as a testbed for expressing an electron transfer pathway naturally occurring in a bacterial species called Shewanella oneidensis MR-1. The engineered E. coli was able to use the protein complex to reduce nanocrystalline iron oxide (Jensen, et al. (2010) PNAS.). Building off of this research, a group led by Caroline Ajo-Franklin, a staff scientist in the Biological Nanostructures Facility at Berkeley Lab’s Molecular Foundry studying synthetic biology, has now demonstrated that these engineered E. coli strains can generate measurable current at an anode.

The results of this new study, Tuning promoter strengths for improved synthesis and function of electron conduits in Escherichia coli, have recently been published in ACS Synthetic Biology, the American Chemical Society’s new flagship journal for synthetic biology.

Authors of the recent publication in the Biological Nanostructures Laboratory. From left to right: Caroline Ajo-Franklin, Heather Jensen, Matt Hepler, Cheryl Goldbeck

See the full article here.

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From Berkeley Lab: “Reading the Human Genome”

Berkeley Lab

Berkeley Lab Researchers Produce First Step-by-Step Look at Transcription Initiation

February 27, 2013
Lynn Yarris

Researchers with the U.S. Department of Energy (DOE)’s Lawrence Berkeley National Laboratory (Berkeley Lab) have achieved a major advance in understanding how genetic information is transcribed from DNA to RNA by providing the first step-by-step look at the biomolecular machinery that reads the human genome.

‘We’ve provided a series of snapshots that shows how the genome is read one gene at a time,’ says biophysicist Eva Nogales who led this research. ‘For the genetic code to be transcribed into messenger RNA, the DNA double helix has to be opened and the strand of gene sequences has to be properly positioned so that RNA polymerase, the enzyme that catalyzes transcription, knows where the gene starts. The electron microscopy images we produced show how this is done.’

Says Paula Flicker of the National Institutes of Health’s National Institute of General Medical Sciences, which partly funded the research, ‘The process of transcription is essential to all living things so understanding how it initiates is enormously important. This work is a beautiful example of integrating multiple approaches to reveal the structure of a large molecular complex and provide insight into the molecular basis of a fundamental cellular process.’”

Eva Nogales and Yuan He used cryo-electron microscopy to record how a complex of biomolecules is able to read the human genome one gene at a time. (Photo by Roy Kaltschmidt)

See the full article here.

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From Berkeley Lab: “New Opportunities for Crystal Growth”

Berkeley Lab

Berkeley Lab Facility Provides Unique Capabilities for the Synthesis of New Crystals and Materials

February 25, 2013
Lynn Yarris

“Talk with material scientist Edith Bourret-Courchesne about what it takes to grow and develop useful crystals and a word you will hear repeated often is “patience.” As the leader of a unique crystal growth facility at Lawrence Berkeley National Laboratory (Berkeley Lab) dedicated to the synthesis of crystals and new materials, patience is more than a virtue, it’s a necessity.

Edith Bourret-Courchesne, Berkeley Lab materials scientist, heads a facility that provides a wide range of crystal purification, growth and characterization capabilities. (Photo by Roy Kaltschmidt)

‘The growth of every crystal is unique, like the formation of a snowflake, and since we work with compounds that have never before been crystallized the processes by which we grow our crystals are also unique,’ she says. ‘As a result, a lot of our research is aimed at understanding why something didn’t work.’

Bourret-Courchesne is a senior scientist with Berkeley Lab’s Materials Sciences Division where she has been studying the synthesis of new crystals and materials since 1984…In 2008, Bourret-Courchesne’s crystal growth research effort received a much welcomed boost in the form of a grant from the U.S. Department of Energy (DOE) through the National Nuclear Security Agency (NNSA). This NNSA grant enabled Berkeley Lab to acquire the capabilities needed to grow and develop new single crystals as high-performance scintillators that can be used for the detection of nuclear materials.”

See the full very informative article here.

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From Berkeley Lab: “Gordon and Betty Moore Foundation Gives a Big Boost to BigBOSS”

Berkeley Lab

$2.1 Million Grant to Berkeley Center for Cosmological Physics advances dark energy research at UC Berkeley and Berkeley Lab

December 04, 2012
Paul Preuss

“A $2.1 million grant from the Gordon and Betty Moore Foundation to the University of California at Berkeley, through the Berkeley Center for Cosmological Physics (BCCP), will fund the development of revolutionary technologies for BigBOSS, a project now in the proposal stage designed to study dark energy with unprecedented precision. BigBOSS is based at the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab).

The BigBOSS proposal adds a new widefield, prime-focus corrector to the Mayall 4-meter telescope. A focal array with 5,000 optical fibers, individually positioned by robotic actuators, delivers light to a set of 10 three-arm spectrometers. (Lawrence Berkeley National Laboratory. Background photo Mark Duggan)

‘BigBOSS is the next big thing in cosmology,’ says Uroš Seljak, Director of the BCCP, who is a professor of physics and astronomy at UC Berkeley and a member of Berkeley Lab’s Physics Division. ‘It would map millions and millions of galaxies, allowing us to measure dark energy to high precision – and would yield other important scientific results as well, including determining neutrino mass and the number of neutrino families.’”

See the full article here.

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From Berkeley Lab: “Searching for the Solar System’s Chemical Recipe”

Berkeley Lab

Berkeley Lab’s Chemical Dynamics Beamline points to why isotope ratios in interplanetary dust and meteorites differ from Earth’s

February 20, 2013
Paul Preuss

The protosun evolved in a hot nebula of infalling gas and dust that formed an accretion disk (green) of surrounding matter. Visible and ultraviolet light poured from the sun, irradiating abundant clouds of carbon monoxide, hydrogen sulfide, and other chemicals. Temperatures near the sun were hot enough to melt silicates and other minerals, forming the chondrules found in early meteoroids (dashed black circles). Beyond the “snowline” (dashed white curves), water, methane, and other compounds condensed to ice. Numerous chemical reactions contributed to the isotopic ratios seen in relics of the early solar system today. No image credit.

“By studying the origins of different isotope ratios among the elements that make up today’s smorgasbord of planets, moons, comets, asteroids, and interplanetary ice and dust, Mark Thiemens and his colleagues hope to learn how our solar system evolved. Thiemens, Dean of the Division of Physical Sciences at the University of California, San Diego, has worked on this problem for over three decades.

In recent years his team has found the Chemical Dynamics Beamline of the Advanced Light Source (ALS) at the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) to be an invaluable tool for examining how photochemistry determines the basic ingredients in the solar system recipe.

‘Mark and his colleagues Subrata Chakraborty and Teresa Jackson wanted to know if photochemistry could explain some of the differences in isotope ratios between Earth and what’s found in meteorites and interplanetary dust particles,’ says Musahid (Musa) Ahmed of Berkeley Lab’s Chemical Sciences Division, a scientist at the Chemical Dynamics Beamline who works with the UC San Diego team. ‘They needed a source of ultraviolet light powerful enough to dissociate gas molecules like carbon monoxide, hydrogen sulfide, and nitrogen. That’s us: our beamline basically provides information about gas-phase photodynamics.’”

See the full article here.

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From Berkeley Lab: “A Cyclotron’s Long Journey Home”

Berkeley Lab

One of the world’s first working circular particle accelerators returns to Berkeley Lab—75 years later.

February 19, 2013
Julie Chao

Seventy-five years after one of the world’s first working cyclotrons was handed to the London Science Museum, it has returned to its birthplace in the Berkeley hills, where the man who invented it, Ernest O. Lawrence, helped launch the field of modern particle physics as well as the national laboratory that would bear his name, Lawrence Berkeley National Laboratory.

Ernest O. Lawrence

On Jan. 9, 1932 the brass cyclotron—which measures 26 inches from end to end and whose accelerating chamber measures just 11 inches in diameter—was successfully used to boost protons to energies of 1.22 million electron volts. Its return to Berkeley Lab caps a decades-long saga in which various parties endeavored to secure the cyclotron’s return from London, but the persistence of Pamela Patterson, who chronicles Berkeley Lab’s history as managing editor of its website, finally paid off.

Ernest O. Lawrence’s 11-inch cyclotron has returned to Berkeley Lab after 75 years. No image credit.

Particle accelerators propel electrically charged particles to speeds approaching that of light. Increasing the speed of a particle increases its kinetic energy. Smashing highly energized particles into a target or other particles shatters them and releases their contents for inspection. In this fashion, accelerators serve as incredibly powerful ‘microscopes,’ allowing scientists to observe our universe at the level where its deepest secrets are kept.”

See the full article here.

The Tevatron at Fermilab

The Large Hadron Collider at CERN

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