From DOE’s Lawrence Berkeley National Laboratory (US) and University of California-Berkeley (US) : “This Exotic Particle Had an Out-of-Body Experience; These Scientists Took a Picture of It”

From DOE’s Lawrence Berkeley National Laboratory (US)

and

University of California-Berkeley (US)

August 19, 2021
Theresa Duque
tnduque@lbl.gov
(510) 495-2418

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Artist’s illustration of ghost particles moving through a quantum spin liquid. Credit: Jenny Nuss/Berkeley Lab.

Scientists have taken the clearest picture yet of electronic particles that make up a mysterious magnetic state called a quantum spin liquid (QSL).

The achievement could facilitate the development of superfast quantum computers and energy-efficient superconductors.

The scientists are the first to capture an image of how electrons in a QSL decompose into spin-like particles called spinons and charge-like particles called chargons.

“Other studies have seen various footprints of this phenomenon, but we have an actual picture of the state in which the spinon lives. This is something new,” said study leader Mike Crommie, a senior faculty scientist at Lawrence Berkeley National Laboratory (Berkeley Lab) and physics professor at University of California-Berkeley (US).

“Spinons are like ghost particles. They are like the Big Foot of quantum physics – people say that they’ve seen them but it’s hard to prove that they exist,” said co-author Sung-Kwan Mo, a staff scientist at Berkeley Lab’s Advanced Light Source [below]. “With our method we’ve provided some of the best evidence to date.”

A surprise catch from a quantum wave

In a QSL spinons freely move about carrying heat and spin but no electrical charge. To detect them, most researchers have relied on techniques that look for their heat signatures.

Now, as reported in the journal Nature Physics, Crommie, Mo, and their research teams have demonstrated how to characterize spinons in QSLs by directly imaging how they are distributed in a material.

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Schematic of the triangular spin lattice and star-of-David charge density wave pattern in a monolayer of tantalum diselenide. Each star consists of 13 tantalum atoms. Localized spins are represented by a blue arrow at the star center. The wavefunction of the localized electrons is represented by gray shading. Credit: Mike Crommie et al./Berkeley Lab.

To begin the study, Mo’s group at Berkeley Lab’s Advanced Light Source (ALS)[below] grew single-layer samples of tantalum diselenide (1T-TaSe2) that are only three-atoms thick. This material is part of a class of materials called transition metal dichalcogenides (TMDCs). The researchers in Mo’s team are experts in molecular beam epitaxy, a technique for synthesizing atomically thin TMDC crystals from their constituent elements.

Mo’s team then characterized the thin films through angle-resolved photoemission spectroscopy, a technique that uses X-rays generated at the ALS.

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Scanning tunneling microscopy image of a tantalum diselenide sample that is just 3 atoms thick. Credit: Mike Crommie et al./Berkeley Lab.

Using a microscopy technique called scanning tunneling microscopy (STM), researchers in the Crommie lab – including co-first authors Wei Ruan, a postdoctoral fellow at the time, and Yi Chen, then a UC Berkeley graduate student – injected electrons from a metal needle into the tantalum diselenide TMDC sample.

Images gathered by scanning tunneling spectroscopy (STS) – an imaging technique that measures how particles arrange themselves at a particular energy – revealed something quite unexpected: a layer of mysterious waves having wavelengths larger than one nanometer (1 billionth of a meter) blanketing the material’s surface.

“The long wavelengths we saw didn’t correspond to any known behavior of the crystal,” Crommie said. “We scratched our heads for a long time. What could cause such long wavelength modulations in the crystal? We ruled out the conventional explanations one by one. Little did we know that this was the signature of spinon ghost particles.”

How spinons take flight while chargons stand still.

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Illustration of an electron breaking apart into spinon ghost particles and chargons inside a quantum spin liquid. Credit: Mike Crommie et al./Berkeley Lab.

With help from a theoretical collaborator at Massachusetts Institute of Technology (US), the researchers realized that when an electron is injected into a QSL from the tip of an STM, it breaks apart into two different particles inside the QSL – spinons (also known as ghost particles) and chargons. This is due to the peculiar way in which spin and charge in a QSL collectively interact with each other. The spinon ghost particles end up separately carrying the spin while the chargons separately bear the electrical charge.

In the current study, STM/STS images show that the chargons freeze in place, forming what scientists call a star-of-David charge-density-wave. Meanwhile, the spinons undergo an “out-of-body experience” as they separate from the immobilized chargons and move freely through the material, Crommie said. “This is unusual since in a conventional material, electrons carry both the spin and charge combined into one particle as they move about,” he explained. “They don’t usually break apart in this funny way.”

Crommie added that QSLs might one day form the basis of robust quantum bits (qubits) used for quantum computing. In conventional computing a bit encodes information either as a zero or a one, but a qubit can hold both zero and one at the same time, thus potentially speeding up certain types of calculations. Understanding how spinons and chargons behave in QSLs could help advance research in this area of next-gen computing.

Another motivation for understanding the inner workings of QSLs is that they have been predicted to be a precursor to exotic superconductivity. Crommie plans to test that prediction with Mo’s help at the ALS.

“Part of the beauty of this topic is that all the complex interactions within a QSL somehow combine to form a simple ghost particle that just bounces around inside the crystal,” he said. “Seeing this behavior was pretty surprising, especially since we weren’t even looking for it.”

Researchers from DOE’s SLAC National Accelerator Laboratory (US); Stanford University (US); DOE’s Argonne National Laboratory (US); The Massachusetts Institute of Technology (US); The Chinese Academy of Sciences [中国科学院] (CN), Shanghai Technical University [上海科技大学] (CN), Shenzhen University (SZU)[ 深圳大学](CN), Henan University of Science and Technology [河南科技大学英文版](CN); and the KAIST-Korea Advanced Institute of Science and Technology [한국과학기술원](KR) and Pusan National University[국립 부산 대학교(KR) contributed to this study. (Co-first author Wei Ruan is now an assistant professor of physics at Fudan University (CN); co-first author Yi Chen is currently a postdoctoral fellow at the Center for Quantum Nanoscience, Institute for Basic Science of Korea [ 기초과학연구원](KR).)

See the full article here .

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Please help promote STEM in your local schools.

Stem Education Coalition

The University of California-Berkeley US) is a public land-grant research university in Berkeley, California. Established in 1868 as the state’s first land-grant university, it was the first campus of the University of California (US) system and a founding member of the Association of American Universities (US). Its 14 colleges and schools offer over 350 degree programs and enroll some 31,000 undergraduate and 12,000 graduate students. Berkeley is ranked among the world’s top universities by major educational publications.

Berkeley hosts many leading research institutes, including the Mathematical Sciences Research Institute and the Space Sciences Laboratory. It founded and maintains close relationships with three national laboratories at DOE’s Lawrence Berkeley National Laboratory(US), DOE’s Lawrence Livermore National Laboratory(US) and DOE’s Los Alamos National Lab(US), and has played a prominent role in many scientific advances, from the Manhattan Project and the discovery of 16 chemical elements to breakthroughs in computer science and genomics. Berkeley is also known for student activism and the Free Speech Movement of the 1960s.

Berkeley alumni and faculty count among their ranks 110 Nobel laureates (34 alumni), 25 Turing Award winners (11 alumni), 14 Fields Medalists, 28 Wolf Prize winners, 103 MacArthur “Genius Grant” recipients, 30 Pulitzer Prize winners, and 19 Academy Award winners. The university has produced seven heads of state or government; five chief justices, including Chief Justice of the United States Earl Warren; 21 cabinet-level officials; 11 governors; and 25 living billionaires. It is also a leading producer of Fulbright Scholars, MacArthur Fellows, and Marshall Scholars. Berkeley alumni, widely recognized for their entrepreneurship, have founded many notable companies.

Berkeley’s athletic teams compete in Division I of the NCAA, primarily in the Pac-12 Conference, and are collectively known as the California Golden Bears. The university’s teams have won 107 national championships, and its students and alumni have won 207 Olympic medals.

Made possible by President Lincoln’s signing of the Morrill Act in 1862, the University of California was founded in 1868 as the state’s first land-grant university by inheriting certain assets and objectives of the private College of California and the public Agricultural, Mining, and Mechanical Arts College. Although this process is often incorrectly mistaken for a merger, the Organic Act created a “completely new institution” and did not actually merge the two precursor entities into the new university. The Organic Act states that the “University shall have for its design, to provide instruction and thorough and complete education in all departments of science, literature and art, industrial and professional pursuits, and general education, and also special courses of instruction in preparation for the professions”.

Ten faculty members and 40 students made up the fledgling university when it opened in Oakland in 1869. Frederick H. Billings, a trustee of the College of California, suggested that a new campus site north of Oakland be named in honor of Anglo-Irish philosopher George Berkeley. The university began admitting women the following year. In 1870, Henry Durant, founder of the College of California, became its first president. With the completion of North and South Halls in 1873, the university relocated to its Berkeley location with 167 male and 22 female students.

Beginning in 1891, Phoebe Apperson Hearst made several large gifts to Berkeley, funding a number of programs and new buildings and sponsoring, in 1898, an international competition in Antwerp, Belgium, where French architect Émile Bénard submitted the winning design for a campus master plan.

20th century

In 1905, the University Farm was established near Sacramento, ultimately becoming the University of California-Davis. In 1919, Los Angeles State Normal School became the southern branch of the University, which ultimately became the University of California-Los Angeles. By 1920s, the number of campus buildings had grown substantially and included twenty structures designed by architect John Galen Howard.

In 1917, one of the nation’s first ROTC programs was established at Berkeley and its School of Military Aeronautics began training pilots, including Gen. Jimmy Doolittle. Berkeley ROTC alumni include former Secretary of Defense Robert McNamara and Army Chief of Staff Frederick C. Weyand as well as 16 other generals. In 1926, future fleet admiral Chester W. Nimitz established the first Naval ROTC unit at Berkeley.

In the 1930s, Ernest Lawrence helped establish the Radiation Laboratory (now DOE’s Lawrence Berkeley National Laboratory (US)) and invented the cyclotron, which won him the Nobel physics prize in 1939. Using the cyclotron, Berkeley professors and Berkeley Lab researchers went on to discover 16 chemical elements—more than any other university in the world. In particular, during World War II and following Glenn Seaborg’s then-secret discovery of plutonium, Ernest Orlando Lawrence’s Radiation Laboratory began to contract with the U.S. Army to develop the atomic bomb. Physics professor J. Robert Oppenheimer was named scientific head of the Manhattan Project in 1942. Along with the Lawrence Berkeley National Laboratory, Berkeley founded and was then a partner in managing two other labs, Los Alamos National Laboratory (1943) and Lawrence Livermore National Laboratory (1952).

By 1942, the American Council on Education ranked Berkeley second only to Harvard University (US) in the number of distinguished departments.

In 1952, the University of California reorganized itself into a system of semi-autonomous campuses, with each campus given its own chancellor, and Clark Kerr became Berkeley’s first Chancellor, while Sproul remained in place as the President of the University of California.

Berkeley gained a worldwide reputation for political activism in the 1960s. In 1964, the Free Speech Movement organized student resistance to the university’s restrictions on political activities on campus—most conspicuously, student activities related to the Civil Rights Movement. The arrest in Sproul Plaza of Jack Weinberg, a recent Berkeley alumnus and chair of Campus CORE, in October 1964, prompted a series of student-led acts of formal remonstrance and civil disobedience that ultimately gave rise to the Free Speech Movement, which movement would prevail and serve as precedent for student opposition to America’s involvement in the Vietnam War.

In 1982, the Mathematical Sciences Research Institute (MSRI) was established on campus with support from the National Science Foundation and at the request of three Berkeley mathematicians — Shiing-Shen Chern, Calvin Moore and Isadore M. Singer. The institute is now widely regarded as a leading center for collaborative mathematical research, drawing thousands of visiting researchers from around the world each year.

21st century

In the current century, Berkeley has become less politically active and more focused on entrepreneurship and fundraising, especially for STEM disciplines.

Modern Berkeley students are less politically radical, with a greater percentage of moderates and conservatives than in the 1960s and 70s. Democrats outnumber Republicans on the faculty by a ratio of 9:1. On the whole, Democrats outnumber Republicans on American university campuses by a ratio of 10:1.

In 2007, the Energy Biosciences Institute was established with funding from BP and Stanley Hall, a research facility and headquarters for the California Institute for Quantitative Biosciences, opened. The next few years saw the dedication of the Center for Biomedical and Health Sciences, funded by a lead gift from billionaire Li Ka-shing; the opening of Sutardja Dai Hall, home of the Center for Information Technology Research in the Interest of Society; and the unveiling of Blum Hall, housing the Blum Center for Developing Economies. Supported by a grant from alumnus James Simons, the Simons Institute for the Theory of Computing was established in 2012. In 2014, Berkeley and its sister campus, Univerity of California-San Fransisco (US), established the Innovative Genomics Institute, and, in 2020, an anonymous donor pledged $252 million to help fund a new center for computing and data science.

Since 2000, Berkeley alumni and faculty have received 40 Nobel Prizes, behind only Harvard and Massachusetts Institute of Technology (US) among US universities; five Turing Awards, behind only MIT and Stanford; and five Fields Medals, second only to Princeton University (US). According to PitchBook, Berkeley ranks second, just behind Stanford University, in producing VC-backed entrepreneurs.

UC Berkeley Seal


Bringing Science Solutions to the World

In the world of science, Lawrence Berkeley National Laboratory (Berkeley Lab) (US) is synonymous with “excellence.” Thirteen Nobel prizes are associated with Berkeley Lab. Seventy Lab scientists are members of the National Academy of Sciences (NAS), one of the highest honors for a scientist in the United States. Thirteen of our scientists have won the National Medal of Science, our nation’s highest award for lifetime achievement in fields of scientific research. Eighteen of our engineers have been elected to the National Academy of Engineering, and three of our scientists have been elected into the Institute of Medicine. In addition, Berkeley Lab has trained thousands of university science and engineering students who are advancing technological innovations across the nation and around the world.

Berkeley Lab is a member of the national laboratory system supported by the U.S. Department of Energy through its Office of Science. It is managed by the University of California (US) and is charged with conducting unclassified research across a wide range of scientific disciplines. Located on a 202-acre site in the hills above the UC Berkeley campus that offers spectacular views of the San Francisco Bay, Berkeley Lab employs approximately 3,232 scientists, engineers and support staff. The Lab’s total costs for FY 2014 were $785 million. A recent study estimates the Laboratory’s overall economic impact through direct, indirect and induced spending on the nine counties that make up the San Francisco Bay Area to be nearly $700 million annually. The Lab was also responsible for creating 5,600 jobs locally and 12,000 nationally. The overall economic impact on the national economy is estimated at $1.6 billion a year. Technologies developed at Berkeley Lab have generated billions of dollars in revenues, and thousands of jobs. Savings as a result of Berkeley Lab developments in lighting and windows, and other energy-efficient technologies, have also been in the billions of dollars.

Berkeley Lab was founded in 1931 by Ernest Orlando Lawrence, a University of California-Berkeley (US) physicist who won the 1939 Nobel Prize in physics for his invention of the cyclotron, a circular particle accelerator that opened the door to high-energy physics. It was Lawrence’s belief that scientific research is best done through teams of individuals with different fields of expertise, working together. His teamwork concept is a Berkeley Lab legacy that continues today.

History

1931–1941

The laboratory was founded on August 26, 1931, by Ernest Lawrence, as the Radiation Laboratory of the University of California, Berkeley, associated with the Physics Department. It centered physics research around his new instrument, the cyclotron, a type of particle accelerator for which he was awarded the Nobel Prize in Physics in 1939.

LBNL 88 inch cyclotron.


Throughout the 1930s, Lawrence pushed to create larger and larger machines for physics research, courting private philanthropists for funding. He was the first to develop a large team to build big projects to make discoveries in basic research. Eventually these machines grew too large to be held on the university grounds, and in 1940 the lab moved to its current site atop the hill above campus. Part of the team put together during this period includes two other young scientists who went on to establish large laboratories; J. Robert Oppenheimer founded DOE’s Los Alamos Laboratory (US), and Robert Wilson founded Fermi National Accelerator Laboratory(US).

1942–1950

Leslie Groves visited Lawrence’s Radiation Laboratory in late 1942 as he was organizing the Manhattan Project, meeting J. Robert Oppenheimer for the first time. Oppenheimer was tasked with organizing the nuclear bomb development effort and founded today’s Los Alamos National Laboratory to help keep the work secret. At the RadLab, Lawrence and his colleagues developed the technique of electromagnetic enrichment of uranium using their experience with cyclotrons. The “calutrons” (named after the University) became the basic unit of the massive Y-12 facility in Oak Ridge, Tennessee. Lawrence’s lab helped contribute to what have been judged to be the three most valuable technology developments of the war (the atomic bomb, proximity fuse, and radar). The cyclotron, whose construction was stalled during the war, was finished in November 1946. The Manhattan Project shut down two months later.

1951–2018

After the war, the Radiation Laboratory became one of the first laboratories to be incorporated into the Atomic Energy Commission (AEC) (now Department of Energy (US). The most highly classified work remained at Los Alamos, but the RadLab remained involved. Edward Teller suggested setting up a second lab similar to Los Alamos to compete with their designs. This led to the creation of an offshoot of the RadLab (now the Lawrence Livermore National Laboratory (US)) in 1952. Some of the RadLab’s work was transferred to the new lab, but some classified research continued at Berkeley Lab until the 1970s, when it became a laboratory dedicated only to unclassified scientific research.

Shortly after the death of Lawrence in August 1958, the UC Radiation Laboratory (both branches) was renamed the Lawrence Radiation Laboratory. The Berkeley location became the Lawrence Berkeley Laboratory in 1971, although many continued to call it the RadLab. Gradually, another shortened form came into common usage, LBNL. Its formal name was amended to Ernest Orlando Lawrence Berkeley National Laboratory in 1995, when “National” was added to the names of all DOE labs. “Ernest Orlando” was later dropped to shorten the name. Today, the lab is commonly referred to as “Berkeley Lab”.

The Alvarez Physics Memos are a set of informal working papers of the large group of physicists, engineers, computer programmers, and technicians led by Luis W. Alvarez from the early 1950s until his death in 1988. Over 1700 memos are available on-line, hosted by the Laboratory.

The lab remains owned by the Department of Energy (US), with management from the University of California (US). Companies such as Intel were funding the lab’s research into computing chips.

Science mission

From the 1950s through the present, Berkeley Lab has maintained its status as a major international center for physics research, and has also diversified its research program into almost every realm of scientific investigation. Its mission is to solve the most pressing and profound scientific problems facing humanity, conduct basic research for a secure energy future, understand living systems to improve the environment, health, and energy supply, understand matter and energy in the universe, build and safely operate leading scientific facilities for the nation, and train the next generation of scientists and engineers.

The Laboratory’s 20 scientific divisions are organized within six areas of research: Computing Sciences; Physical Sciences; Earth and Environmental Sciences; Biosciences; Energy Sciences; and Energy Technologies. Berkeley Lab has six main science thrusts: advancing integrated fundamental energy science; integrative biological and environmental system science; advanced computing for science impact; discovering the fundamental properties of matter and energy; accelerators for the future; and developing energy technology innovations for a sustainable future. It was Lawrence’s belief that scientific research is best done through teams of individuals with different fields of expertise, working together. His teamwork concept is a Berkeley Lab tradition that continues today.

Berkeley Lab operates five major National User Facilities for the DOE Office of Science (US):

The Advanced Light Source (ALS) is a synchrotron light source with 41 beam lines providing ultraviolet, soft x-ray, and hard x-ray light to scientific experiments.

LBNL/ALS


The ALS is one of the world’s brightest sources of soft x-rays, which are used to characterize the electronic structure of matter and to reveal microscopic structures with elemental and chemical specificity. About 2,500 scientist-users carry out research at ALS every year. Berkeley Lab is proposing an upgrade of ALS which would increase the coherent flux of soft x-rays by two-three orders of magnitude.

The DOE Joint Genome Institute (US) supports genomic research in support of the DOE missions in alternative energy, global carbon cycling, and environmental management. The JGI’s partner laboratories are Berkeley Lab, DOE’s Lawrence Livermore National Laboratory (US), DOE’s Oak Ridge National Laboratory (US)(ORNL), DOE’s Pacific Northwest National Laboratory (US) (PNNL), and the HudsonAlpha Institute for Biotechnology (US). The JGI’s central role is the development of a diversity of large-scale experimental and computational capabilities to link sequence to biological insights relevant to energy and environmental research. Approximately 1,200 scientist-users take advantage of JGI’s capabilities for their research every year.

The LBNL Molecular Foundry (US) [above] is a multidisciplinary nanoscience research facility. Its seven research facilities focus on Imaging and Manipulation of Nanostructures; Nanofabrication; Theory of Nanostructured Materials; Inorganic Nanostructures; Biological Nanostructures; Organic and Macromolecular Synthesis; and Electron Microscopy. Approximately 700 scientist-users make use of these facilities in their research every year.

The DOE’s NERSC National Energy Research Scientific Computing Center (US) is the scientific computing facility that provides large-scale computing for the DOE’s unclassified research programs. Its current systems provide over 3 billion computational hours annually. NERSC supports 6,000 scientific users from universities, national laboratories, and industry.

DOE’s NERSC National Energy Research Scientific Computing Center(US) at Lawrence Berkeley National Laboratory

The Genepool system is a cluster dedicated to the DOE Joint Genome Institute’s computing needs. Denovo is a smaller test system for Genepool that is primarily used by NERSC staff to test new system configurations and software.

PDSF is a networked distributed computing cluster designed primarily to meet the detector simulation and data analysis requirements of physics, astrophysics and nuclear science collaborations.

NERSC is a DOE Office of Science User Facility.

The DOE’s Energy Science Network (US) is a high-speed network infrastructure optimized for very large scientific data flows. ESNet provides connectivity for all major DOE sites and facilities, and the network transports roughly 35 petabytes of traffic each month.

Berkeley Lab is the lead partner in the DOE’s Joint Bioenergy Institute (US) (JBEI), located in Emeryville, California. Other partners are the DOE’s Sandia National Laboratory (US), the University of California (UC) campuses of Berkeley and Davis, the Carnegie Institution for Science (US), and DOE’s Lawrence Livermore National Laboratory (US) (LLNL). JBEI’s primary scientific mission is to advance the development of the next generation of biofuels – liquid fuels derived from the solar energy stored in plant biomass. JBEI is one of three new U.S. Department of Energy (DOE) Bioenergy Research Centers (BRCs).

Berkeley Lab has a major role in two DOE Energy Innovation Hubs. The mission of the Joint Center for Artificial Photosynthesis (JCAP) is to find a cost-effective method to produce fuels using only sunlight, water, and carbon dioxide. The lead institution for JCAP is the California Institute of Technology (US) and Berkeley Lab is the second institutional center. The mission of the Joint Center for Energy Storage Research (JCESR) is to create next-generation battery technologies that will transform transportation and the electricity grid. DOE’s Argonne National Laboratory (US) leads JCESR and Berkeley Lab is a major partner.