This research was supported by the U.S. Department of Energy, the National Science Foundation, the Gordon and Betty Moore Foundation, the Fundacion Ramon Areces, and the CIFAR Quantum Materials Program. END
"Magic-angle" trilayer graphene may be a rare, magnet-proof superconductor
New findings might help inform the design of more powerful MRI machines or robust quantum computers.
(Press-News.org) MIT physicists have observed signs of a rare type of superconductivity in a material called magic-angle twisted trilayer graphene. In a study appearing in Nature, the researchers report that the material exhibits superconductivity at surprisingly high magnetic fields of up to 10 Tesla, which is three times higher than what the material is predicted to endure if it were a conventional superconductor. The results strongly imply that magic-angle trilayer graphene, which was initially discovered by the same group, is a very rare type of superconductor, known as a "spin-triplet," that is impervious to high magnetic fields. Such exotic superconductors could vastly improve technologies such as magnetic resonance imaging, which uses superconducting wires under a magnetic field to resonate with and image biological tissue. MRI machines are currently limited to magnet fields of 1 to 3 Tesla. If they could be built with spin-triplet superconductors, MRI could operate under higher magnetic fields to produce sharper, deeper images of the human body. The new evidence of spin-triplet superconductivity in trilayer graphene could also help scientists design stronger superconductors for practical quantum computing. "The value of this experiment is what it teaches us about fundamental superconductivity, about how materials can behave, so that with those lessons learned, we can try to design principles for other materials which would be easier to manufacture, that could perhaps give you better superconductivity," says Pablo Jarillo-Herrero, the Cecil and Ida Green Professor of Physics at MIT. His co-authors on the paper include postdoc Yuan Cao and graduate student Jeong Min Park at MIT, and Kenji Watanabe and Takashi Taniguchi of the National Institute for Materials Science in Japan. Strange shift Superconducting materials are defined by their super-efficient ability to conduct electricity without losing energy. When exposed to an electric current, electrons in a superconductor couple up in "Cooper pairs" that then travel through the material without resistance, like passengers on an express train. In a vast majority of superconductors, these passenger pairs have opposite spins, with one electron spinning up, and the other down -- a configuration known as a "spin-singlet." These pairs happily speed through a superconductor, except under high magnetic fields, which can shift the energy of each electron in opposite directions, pulling the pair apart. In this way, and through mechanisms, high magnetic fields can derail superconductivity in conventional spin-singlet superconductors. "That's the ultimate reason why in a large-enough magnetic field, superconductivity disappears," Park says. But there exists a handful of exotic superconductors that are impervious to magnetic fields, up to very large strengths. These materials superconduct through pairs of electrons with the same spin -- a property known as "spin-triplet." When exposed to high magnetic fields, the energy of both electrons in a Cooper pair shift in the same direction, in a way that they are not pulled apart but continue superconducting unperturbed, regardless of the magnetic field strength. Jarillo-Herrero's group was curious whether magic-angle trilayer graphene might harbor signs of this more unusual spin-triplet superconductivity. The team has produced pioneering work in the study of graphene moiré structures -- layers of atom-thin carbon lattices that, when stacked at specific angles, can give rise to surprising electronic behaviors. The researchers initially reported such curious properties in two angled sheets of graphene, which they dubbed magic-angle bilayer graphene. They soon followed up with tests of trilayer graphene, a sandwich configuration of three graphene sheets that turned out to be even stronger than its bilayer counterpart, retaining superconductivity at higher temperatures. When the researchers applied a modest magnetic field, they noticed that trilayer graphene was able to superconduct at field strengths that would destroy superconductivity in bilayer graphene. "We thought, this is something very strange," Jarillo-Herrero says. A super comeback In their new study, the physicists tested trilayer graphene's superconductivity under increasingly higher magnetic fields. They fabricated the material by peeling away atom-thin layers of carbon from a block of graphite, stacking three layers together, and rotating the middle one by 1.56 degrees with respect to the outer layers. They attached an electrode to either end of the material to run a current through and measure any energy lost in the process. Then they turned on a large magnet in the lab, with a field which they oriented parallel to the material. As they increased the magnetic field around trilayer graphene, they observed that superconductivity held strong up to a point before disappearing, but then curiously reappeared at higher field strengths -- a comeback that is highly unusual and not known to occur in conventional spin-singlet superconductors. "In spin-singlet superconductors, if you kill superconductivity, it never comes back -- it's gone for good," Cao says. "Here, it reappeared again. So this definitely says this material is not spin-singlet." They also observed that after "re-entry," superconductivity persisted up to 10 Tesla, the maximum field strength that the lab's magnet could produce. This is about three times higher than what the superconductor should withstand if it were a conventional spin-singlet, according to Pauli's limit, a theory that predicts the maximum magnetic field at which a material can retain superconductivity. Trilayer graphene's reappearance of superconductivity, paired with its persistence at higher magnetic fields than predicted, rules out the possibility that the material is a run-of-the-mill superconductor. Instead, it is likely a very rare type, possibly a spin-triplet, hosting Cooper pairs that speed through the material, impervious to high magnetic fields. The team plans to drill down on the material to confirm its exact spin state, which could help to inform the design of more powerful MRI machines, and also more robust quantum computers. "Regular quantum computing is super fragile," Jarillo-Herrero says. "You look at it and, poof, it disappears. About 20 years ago, theorists proposed a type of topological superconductivity that, if realized in any material, could [enable] a quantum computer where states responsible for computation are very robust. That would give infinite more power to do computing. The key ingredient to realize that would be spin-triplet superconductors, of a certain type. We have no idea if our type is of that type. But even if it's not, this could make it easier to put trilayer graphene with other materials to engineer that kind of superconductivity. That could be a major breakthrough. But it's still super early."
ELSE PRESS RELEASES FROM THIS DATE:
Association between COVID-19 exposure, self-reported compliance with public health guidelines among essential employees at an institution of higher education
What The Study Did: This study at an institution of higher education in Colorado evaluated the association between self-reported protective behaviors and how common SARS-CoV-2 infection was among essential in-person employees during the first six months of the COVID-19 pandemic in the United States. Authors: Tracy L. Nelson, M.P.H., Ph.D., of Colorado State University in Fort Collins, is the corresponding author. To access the embargoed study: Visit our For The Media website at this link https://media.jamanetwork.com/ (doi:10.1001/jamanetworkopen.2021.16543) Editor's Note: The article includes conflict of interest and funding/support disclosures. ...
Gender-affirming hair removal, mental health outcomes
What The Study Did: In this analysis of the 2015 U.S. Transgender Survey, gender-affirming hair removal procedures were associated with lower odds of past-month severe psychological distress, past-year smoking and past-year suicidal ideation. Authors: Michelle S. Lee, B.A., of Harvard Medical School in Boston, is the corresponding author. To access the embargoed study: Visit our For The Media website at this link https://media.jamanetwork.com/ (doi:10.1001/jamadermatol.2021.2551) Editor's Note: The article includes conflicts of interest ...
Preventing approximal caries in primary teeth with topical fluorides
Alexandria, Va., USA - Parach Sirivichayakul, Mahidol University, Bangkok, Thailand, presented the poster "Preventing Approximal Caries in Primary Teeth With Topical Fluorides" at the virtual 99th General Session & Exhibition of the International Association for Dental Research (IADR), held in conjunction with the 50th Annual Meeting of the American Association for Dental Research (AADR) and the 45th Annual Meeting of the Canadian Association for Dental Research (CADR), on July 21-24, 2021. There is limited evidence regarding the use of silver diamine fluoride (SDF) for caries prevention in primary teeth. This randomized clinical trial evaluated the effectiveness of 38% SDF, 5% sodium fluoride (NaF) varnish and ...
Researchers discover a 'layer hall effect' in a 2D topological Axion antiferromagnet
Chestnut Hill, Mass. (7/21/2021) - Researchers have discovered a "layer" Hall effect in a solid state chip constructed of antiferromagnetic manganese bismuth telluride, a finding that signals a much sought-after topological Axion insulating state, the team reports in the current edition of the journal Nature. Researchers have been trying to find evidence of a topological Axion insulating (TAI) state and developed some candidate materials based on theoretical calculations. The layered Hall effect represents the first clear experimental evidence of the state, a feature bound by the laws of quantum physics, according to Boston College Assistant Professor ...
City-funded housing repairs in low-income neighborhoods associated with drop in crime
PHILADELPHIA--Investing in structural home repairs in historically segregated, low-income, Black and Latino neighborhoods has been associated with reduced crime rates. In Philadelphia, when a home received repairs through a city-funded program, total crime dropped by 21.9% on that block, and as the number of repaired houses on a block increased, instances of crime fell even further, according to research from the Perelman School of Medicine at the University of Pennsylvania published today in JAMA Network Open. In an effort to address an old housing stock and high levels of historical disinvestment in Philadelphia, the city implemented the Basic Systems Repair ...
Glass sponges have properties for the design of ships, planes and skyscrapers
Rome (Italy), July 21st, 2021 - The remarkable structural properties of the basket sponge (E. aspergillum) might seem fathoms removed from human-engineered structures. However, insights into how the organism's latticework of holes and ridges influences the hydrodynamics of seawater in its vicinity could lead to advanced designs for buildings, bridges, marine vehicles and aircraft, and anything that must respond safely to forces imposed by the flow of air or water. While past research has investigated the structure of the sponge, there have been few studies of the hydrodynamic fields ...
The need for nuance in carbohydrate recommendations
Carbohydrates have traditionally been the largest source of energy intake for much of the world's population1. However, without a standard definition for carbohydrate quality, some foods that contain carbohydrates are often stigmatized based on isolated and reductionist assessment methods that fail to consider their contributions to nutrient intakes and balanced, healthy diets. A new perspective piece, published in Advances in Nutrition, brings to light the pressing need to define carbohydrate quality, to better assess the value of nutrient-dense carbohydrate-containing foods in healthy lifestyles. Ultimately, the authors call for a more holistic approach to carbohydrate guidance to address the complex ...
Traditional Japanese food may hold building blocks of COVID-19 treatments
Natto, a fermented soybean dish often served for breakfast in Japan, originated at the turn of the last millennium but may hold an answer to a modern problem: COVID-19, according to a new study based on cell cultures. Long thought to contribute to longer, healthier lives across Japan -- the country with the longest life expectancy on Earth and home to more than a quarter of the world's population aged 65 years or older -- natto was previously found to be a diet staple in those who were least likely to die from stroke or cardiac disease. Now, researchers have found that extract made from the sticky, strong smelling natto may inhibit the ability of the virus that causes COVID-19 to infect cells. The team published its results on July 13th in Biochemical and Biophysical Research Communications. ...
Researchers discover nucleotide sequence responsible for effectively fighting pathologies
Researchers from HSE University have discovered nucleotide sequences characteristic of microRNA isoforms (microRNAs with errors). The discovery will help predict errors in microRNA behaviour and create drugs that can detect targets (such as viruses) more effectively. The results of the study have been published in the RNA Biology journal. MicroRNAs (miRNAs) are very small molecules that regulate all the processes in a cell, including the transformation of inherited information in RNA or proteins (gene expression). Each microRNA has its own unique set of targets--genes whose activity it can suppress. Recent studies show that even slight changes in microRNA nucleotide sequences (so-called microRNA isoforms or isomiRs) can completely rebuild numerous targets. This can drastically ...
A novel method for the rapid repair of peripheral nerve injuries
Each year, hundreds of thousands of people worldwide suffer from peripheral nerve injuries, which often leave them with long-term disabilities. The peripheral nervous system is analogous to the circulatory system; a network of vessels that reaches all parts of the body, but instead of blood flowing through vessels, electrical signals propagate information through thin fibers called axons, which are engulfed within nerve trunks. These nerve trunks are the communication network relaying information from all parts of the body to the brain, coordinating activity, and generating motor and sensory function. If one of the nerve trunks is damaged or torn - a common condition in limb injuries ...
LAST 30 PRESS RELEASES:
Scientists model 'true prevalence' of COVID-19 throughout pandemic
New breakthrough to help immune systems in the fight against cancer
Through the thin-film glass, researchers spot a new liquid phase
Administering opioids to pregnant mice alters behavior and gene expression in offspring
Brain's 'memory center' needed to recognize image sequences but not single sights
Safety of second dose of mRNA COVID-19 vaccines after first-dose allergic reactions
Changes in disparities in access to care, health after Medicare eligibility
Use of high-risk medications among lonely older adults
65+ and lonely? Don't talk to your doctor about another prescription
Exosome formulation developed to deliver antibodies for choroidal neovascularization therapy
Second COVID-19 mRNA vaccine dose found safe following allergic reactions to first dose
Plant root-associated bacteria preferentially colonize their native host-plant roots
Rare inherited variants in previously unsuspected genes may confer significant risk for autism
International experts call for a unified public health response to NAFLD and NASH epidemic
International collaboration of scientists rewrite the rulebook of flowering plant genetics
Improving air quality reduces dementia risk, multiple studies suggest
Misplaced trust: When trust in science fosters pseudoscience
Two types of blood pressure meds prevent heart events equally, but side effects differ
New statement provides path to include ethnicity, ancestry, race in genomic research
Among effective antihypertensive drugs, less popular choice is slightly safer
Juicy past of favorite Okinawan fruit revealed
Anticipate a resurgence of respiratory viruses in young children
Anxiety, depression, burnout rising as college students prepare to return to campus
Goal-setting and positive parent-child relationships reduce risk of youth vaping
New research identifies cancer types with little survival improvements in adolescents and young adul
Oncotarget: Replication-stress sensitivity in breast cancer cells
Oncotarget: TERT and its binding protein: overexpression of GABPA/B in gliomas
Development of a novel technology to check body temperature with smartphone camera
The mechanics of puncture finally explained
Extreme heat, dry summers main cause of tree death in Colorado's subalpine forests[Press-News.org] "Magic-angle" trilayer graphene may be a rare, magnet-proof superconductor
New findings might help inform the design of more powerful MRI machines or robust quantum computers.