. Scientific Frontline: Physics
Showing posts with label Physics. Show all posts
Showing posts with label Physics. Show all posts

Thursday, May 18, 2023

'Charge Density Wave' Linked to Atomic Distortions in Would-be Superconductor

This image shows the positions of atoms (blue spheres) that make up the crystal lattice of a copper-oxide superconductor, superimposed on a map of electronic charge distribution (yellow is high charge density, dark spots are low) in charge-ordered states. Normally, the atoms can vibrate side-to-side (shadows represent average locations when vibrating). But when cooled to the point where the ladder-like charge density wave appears, the atomic positions shift along the "rungs" and the vibrations cease, locking the atoms in place. Understanding these charge-ordered states may help scientists unlock other interactions that trigger superconductivity at lower temperatures.
Illustration Credit: Courtesy of Brookhaven National Laboratory

Precision measurements reveal connection between electron density and atomic arrangements in charge-ordered states of a superconducting copper-oxide material

What makes some materials carry current with no resistance? Scientists are trying to unravel the complex characteristics. Harnessing this property, known as superconductivity, could lead to perfectly efficient power lines, ultrafast computers, and a range of energy-saving advances. Understanding these materials when they aren’t superconducting is a key part of the quest to unlock that potential.

“To solve the problem, we need to understand the many phases of these materials,” said Kazuhiro Fujita, a physicist in the Condensed Matter Physics & Materials Science Department of the U.S. Department of Energy’s Brookhaven National Laboratory. In a new study just published in Physical Review X, Fujita and his colleagues sought to find an explanation for an oddity observed in a phase that coexists with the superconducting phase of a copper-oxide superconductor.

Wednesday, May 17, 2023

Curved spacetime in a quantum simulator

   In the background: the gravitational lens effect, an example of an effect explained by relativity. With quantum particles, analogous effects can be studied.
Image Credit: NASA / TU Wien

New techniques can answer questions that were previously inaccessible experimentally - including questions about the relationship between quantum mechanics and relativity.

The theory of relativity works well when you want to explain cosmic-scale phenomena - such as the gravitational waves created when black holes collide. Quantum theory works well when describing particle-scale phenomena - such as the behavior of individual electrons in an atom. But combining the two in a completely satisfactory way has yet to be achieved. The search for a "quantum theory of gravity" is considered one of the significant unsolved tasks of science.

This is partly because the mathematics in this field is highly complicated. At the same time, it is tough to perform suitable experiments:  One would have to create situations in which phenomena of both the relativity theory play an important role, for example, a spacetime curved by heavy masses, and at the same time, quantum effects become visible, for example the dual particle and wave nature of light.

Friday, May 12, 2023

Ultralow temperature terahertz microscope capabilities enable better quantum technology

Terahertz microscope with cryogenic insert.
Image Credit: Courtesy of Ames National Laboratory

A team of scientists from the Department of Energy’s Ames National Laboratory have developed a way to collect terahertz imaging data on materials under extreme magnetic and cryogenic conditions. They accomplished their work with a new scanning probe microscope. 

This microscope was recently developed at Ames Lab. The team used the ultralow temperature terahertz microscope to take measurements on superconductors and topological semimetals. These materials were exposed to high magnetic fields and temperatures below liquid helium (below 4.2 Kelvins or -452 degrees Fahrenheit).

According to Jigang Wang, a scientist at Ames Lab, professor of Physics and Astronomy at Iowa State University, and the team leader, the team has been improving their terahertz microscope since it was first completed in 2019. “We have improved the resolution in terms of the space, time and energy,” said Wang. “We have also simultaneously improved operation to very low temperatures and high magnetic fields.”

Study reveals new ways for exotic quasiparticles to “relax”

By sandwiching bits of perovskite between two mirrors and stimulating them with laser beams, researchers were able to directly control the spin state of quasiparticles known as exciton-polariton pairs, which are hybrids of light and matter.
Illustration Credit: Courtesy of the researchers
(CC BY-NC-ND 3.0)

New findings from a team of researchers at MIT and elsewhere could help pave the way for new kinds of devices that efficiently bridge the gap between matter and light. These might include computer chips that eliminate inefficiencies inherent in today’s versions, and qubits, the basic building blocks for quantum computers, that could operate at room temperature instead of the ultracold conditions needed by most such devices.

The new work, based on sandwiching tiny flakes of a material called perovskite in between two precisely spaced reflective surfaces, is detailed in the journal Nature Communications, in a paper by MIT recent graduate Madeleine Laitz PhD ’22, postdoc Dane deQuilettes, MIT professors Vladimir Bulovic, Moungi Bawendi and Keith Nelson, and seven others.

By creating these perovskite sandwiches and stimulating them with laser beams, the researchers were able to directly control the momentum of certain “quasiparticles” within the system. Known as exciton-polariton pairs, these quasiparticles are hybrids of light and matter. Being able to control this property could ultimately make it possible to read and write data to devices based on this phenomenon.

Thursday, May 11, 2023

With new experimental method, researchers probe spin structure in 2D materials for first time

In the study, researchers describe what they believe to be the first measurement showing direct interaction between electrons spinning in a 2D material and photons coming from microwave radiation.
 Graphic Credit: Jia Li, an assistant professor of physics at Brown.

For two decades, physicists have tried to directly manipulate the spin of electrons in 2D materials like graphene. Doing so could spark key advances in the burgeoning world of 2D electronics, a field where super-fast, small and flexible electronic devices carry out computations based on quantum mechanics.

Standing in the way is that the typical way in which scientists measure the spin of electrons — an essential behavior that gives everything in the physical universe its structure — usually doesn’t work in 2D materials. This makes it incredibly difficult to fully understand the materials and propel forward technological advances based on them. But a team of scientists led by Brown University researchers believe they now have a way around this longstanding challenge. They describe their solution in a new study published in Nature Physics.

In the study, the team — which also include scientists from the Center for Integrated Nanotechnologies at Sandia National Laboratories, and the University of Innsbruck — describe what they believe to be the first measurement showing direct interaction between electrons spinning in a 2D material and photons coming from microwave radiation. Called a coupling, the absorption of microwave photons by electrons establishes a novel experimental technique for directly studying the properties of how electrons spin in these 2D quantum materials — one that could serve as a foundation for developing computational and communicational technologies based on those materials, according to the researchers.

Wednesday, May 10, 2023

Entangled quantum circuits

Par­tial sec­tion of the 30-​meter-long quantum con­nec­tion between two su­per­con­duct­ing cir­cuits. The va­cuum tube (center) con­tains a mi­crowave wave­guide that is cooled to around –273°C and con­nects the two quantum cir­cuits.
Pho­to Credit: ETH Zurich / Daniel Wink­ler

A group of researchers led by Andreas Wallraff, Professor of Solid State Physics at ETH Zurich, has performed a loophole-free Bell test to disprove the concept of “local causality” formulated by Albert Einstein in response to quantum mechanics. By showing that quantum mechanical objects that are far apart can be much more strongly correlated with each other than is possible in conventional systems, the researchers have provided further confirmation for quantum mechanics. What’s special about this experiment is that the researchers were able for the first time to perform it using superconducting circuits, which are considered to be promising candidates for building powerful quantum computers.

Physicists discover ‘stacked pancakes of liquid magnetism’

Physicists at Rice University and Ames Laboratory at Iowa State University discovered “stacked pancakes of liquid magnetism” that arise in some helical magnets due to changes in the arrangement of magnetic dipoles when the material warms. At very low temperatures (bottom panel), the orderly arrangement of dipoles leads to magnetism. At high temperature (top panel), dipoles are disordered and the material is nonmagnetic. Pancakes of liquidlike magnetism (middle panel) arise at an intermediate temperature where magnetic interactions within horizontal 2D layers are much stronger than vertical interactions between layers.
Illustration Credit: M. Butcher, courtesy of A. Nevidomskyy/Rice University

Physicists have discovered “stacked pancakes of liquid magnetism” that may account for the strange electronic behavior of some layered helical magnets.

The materials in the study are magnetic at cold temperatures and become nonmagnetic as they thaw. Experimental physicist Makariy Tanatar of Ames National Laboratory at Iowa State University noticed perplexing electronic behavior in layered helimagnetic crystals and brought the mystery to the attention of Rice theoretical physicist Andriy Nevidomskyy, who worked with Tanatar and former Rice graduate student Matthew Butcher to create a computational model that simulated the quantum states of atoms and electrons in the layered materials.

Monday, May 8, 2023

X-ray beams help researchers learn new tricks from old metals


An intense X-ray beam (in pink) is focused into a small spot on a single nanoscale grain of a platinum electrode (highlighted within the droplet). Diffraction interference patterns from that grain were collected on an X-ray detector (the black screen).
Illustration Credit: Dina Sheyfer, Argonne National Laboratory.

A research team led by the U.S. Department of Energy’s (DOE) Argonne National Laboratory used powerful X-ray beams to unlock a new understanding of materials important to the production and use of hydrogen. The goal is to make hydrogen production and usage more efficient and less expensive, offering a better fuel for transportation and industry.

“Efficient hydrogen production is key,” said Hoydoo You, an Argonne senior physicist. ​“Hydrogen is the lightest energy storage material. Hydrogen can be produced from water using renewable energy or excess energy, transported as a fuel, and converted back to water to produce energy for consumers. Platinum and its alloys are best in catalyzing and boosting the water-splitting process by accelerating the exchange of electrons.”

Understanding and developing materials enabling efficient production and usage of hydrogen are key to the hydrogen economy. The researchers made a first step in developing a tool that enables them to characterize the materials with a new level of detail, ultimately producing the best materials for hydrogen production and use.

Tuesday, May 2, 2023

Quantum Entanglement of Photons Doubles Microscope Resolution

Using a "spooky" phenomenon of quantum physics, Caltech researchers have discovered a way to double the resolution of light microscopes.
Photo Credit: Lance Hayashida/Caltech

In a paper appearing in the journal Nature Communications, a team led by Lihong Wang, Bren Professor of Medical Engineering and Electrical Engineering, shows the achievement of a leap forward in microscopy through what is known as quantum entanglement. Quantum entanglement is a phenomenon in which two particles are linked such that the state of one particle is tied to the state of the other particle regardless of whether the particles are anywhere near each other. Albert Einstein famously referred to quantum entanglement as "spooky action at a distance" because it could not be explained by his relativity theory.

According to quantum theory, any type of particle can be entangled. In the case of Wang's new microscopy technique, dubbed quantum microscopy by coincidence (QMC), the entangled particles are photons. Collectively, two entangled photons are known as a biphoton, and, importantly for Wang's microscopy, they behave in some ways as a single particle that has double the momentum of a single photon.

Since quantum mechanics says that all particles are also waves, and that the wavelength of a wave is inversely related to the momentum of the particle, particles with larger momenta have smaller wavelengths. So, because a biphoton has double the momentum of a photon, its wavelength is half that of the individual photons.

Monday, May 1, 2023

Researchers develop clever algorithm to improve our understanding of particle beams in accelerators

A representation of a particle beam traveling through an accelerator.
Illustration Credit: Greg Stewart/SLAC National Laboratory

The algorithm pairs machine-learning techniques with beam physics equations to avoid massive data crunching.

Whenever SLAC National Accelerator Laboratory’s linear accelerator is on, packs of around a billion electrons each travel together at nearly the speed of light through metal piping. These electron bunches form the accelerator’s particle beam, which is used to study the atomic behavior of molecules, novel materials and many other subjects. But trying to estimate what a particle beam actually looks like as it travels through an accelerator is difficult, often leaving scientists with only a rough approximation of how a beam will behave during an experiment.

Now, researchers at the Department of Energy’s SLAC National Accelerator Laboratory, the DOE’s Argonne National Laboratory and the University of Chicago have developed an algorithm that more precisely predicts a beam’s distribution of particle positions and velocities as it zips through an accelerator. This detailed beam information will help scientists perform their experiments more reliably – a need that is becoming increasingly important as accelerator facilities operate at higher and higher energies and generate more complex beam profiles. The researchers detailed their algorithm and method in April in Physical Review Letters.

Thursday, April 27, 2023

Discovering Hidden Order in Disordered Crystals New Material Analysis Method Combining Resonant X-Ray Diffraction and Solid-State NMR

Researchers at Tokyo Tech have discovered hidden chemical order of the Mo and Nb atoms in disordered Ba7Nb4MoO20, by combining state-of-the-art techniques, including resonant X-ray diffraction and solid-state nuclear magnetic resonance. This study provides valuable insights into how a material's properties, such as ionic conduction, can be heavily influenced by its hidden chemical order. These results would stimulate significant advances in materials science and engineering.

Determining the precise structure of a crystalline solid is a challenging endeavor. Materials properties such as ion conduction and chemical stability, are heavily influenced by the chemical (occupational) order and disorder. However, the techniques that scientists typically use to elucidate unknown crystal structures suffer from serious limitations.

For instance, X-ray and neutron diffraction methods are powerful techniques to reveal the atomic positions and arrangement in the crystal lattice. However, they may not be adequate for distinguishing different atomic species with similar X-ray scattering factors and similar neutron scattering lengths.

Wednesday, April 26, 2023

Paradoxical quantum phenomenon measured for the first time

Photo Credit: © Thomas Schweigler, TU Wien

How do quantum particles share information? A peculiar conjecture about quantum information has been experimentally confirmed at the TU Wien.

Some things are related, others are not. Suppose you randomly select a person from a crowd who is significantly taller than the average. In that case, there is a good chance that they will also weigh more than the average. Statistically, one quantity also contains some information about the other.

Quantum physics allows for even stronger links between different quantities: different particles or parts of an extensive quantum system can "share" a certain amount of information. There are curious theoretical predictions about this: surprisingly, the measure of this "mutual information" does not depend on the size of the system but only on its surface. This surprising result has been confirmed experimentally at the TU Wien and published in "Nature Physics". Theoretical input to the experiment and its interpretation came from the Max-Planck-Institut für Quantenoptik in Garching, FU Berlin, ETH Zürich and New York University.

Material found in smartphone screens can be harnessed to map magnetic fields

Existing magnetic field imaging equipment tends to be large and expensive, but this research marks the next step in the development of quantum sensing.
Photo Credit: Rodion Kutsaiev

Hand-held magnetic field imaging equipment could be used in construction safety and medical diagnostics.

Smartphones could one day become portable quantum sensors thanks to a new chip-scale approach that uses organic light-emitting diodes (OLEDs) to image magnetic fields, with significant implications for use in healthcare and industry settings.  

UNSW researchers from the ARC Centre of Excellence in Exciton Science have demonstrated that OLEDs, a type of semiconductor material commonly found in flat-screen televisions, smartphone screens and other digital displays, can be harnessed to map magnetic fields. 

The latest research, led by Dr Rugang Geng and Professor Dane McCamey from the UNSW School of Physics, has been detailed in Nature Communications

Tuesday, April 25, 2023

Scientists Create a Longer-Lasting Exciton that May Open New Possibilities in Quantum Information Science

Alessandra Lanzara at Berkeley Lab.
Photo Credit: Mark Joseph Hanson

In a new study, scientists have observed long-lived excitons in a topological material, opening intriguing new research directions for optoelectronics and quantum computing. 

Excitons are charge-neutral quasiparticles created when light is absorbed by a semiconductor. Consisting of an excited electron coupled to a lower-energy electron vacancy or hole, an exciton is typically short-lived, surviving only until the electron and hole recombine, which limits its usefulness in applications. 

“If we want to make progress in quantum computing and create more sustainable electronics, we need longer exciton lifetimes and new ways of transferring information that don’t rely on the charge of electrons,” said Alessandra Lanzara, who led the study. Lanzara is a senior faculty scientist at the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) and a UC Berkeley physics professor. “Here we’re leveraging topological material properties to make an exciton that is long lived and very robust to disorder.” 

In a topological insulator, electrons can only move on the surface. By creating an exciton in such a material, the researchers hoped to achieve a state in which an electron trapped on the surface was coupled to a hole that remained confined in the bulk. Such a state would be spatially indirect – extending from the surface into the bulk – and could retain the special spin properties inherent to topological surface states. 

Condensed Matter Physics Inspires a New Model of Cellular Behavior

Model illustrating how cells exert pressure on one another, leading to extrusion.
Image Credit: Courtesy of S. Monfared

Cells are expert cooperators and collaborators. To maintain tissue health, cells talk to each other, exert pressure on each other, and kick out cells that are not contributing to the overall well-being of the collective. When it's time to get rid of a cell, the collective group initiates a process called cell extrusion. Cells can be extruded for a number of reasons—they could be cancerous, or old, or they simply could be overcrowding other cells. Extrusion is a necessary process for tissues to maintain health and integrity.

Biologists have long studied the biochemical cues and signals that underly cell extrusion, but the mechanical, physical forces involved are poorly understood.

Now, inspired by the mechanics of a phase of matter called liquid crystals, researchers have developed the first three-dimensional model of a layer of cells and the extrusion behavior that emerges from their physical interactions. From this new model, the team discovered that the more a cell is squeezed by its neighbors in a particular symmetric way, the more likely it is to get extruded from the group.

Thursday, April 20, 2023

Dark order in the universe

3D position and shape information for each galaxy helped to measure the magnitude of alignment relative to distant galaxies
Illustration Credit: KyotoU/Jake Tobiyama

Einstein would nod in approval. General relativity may apply even in the farthest reaches of the universe.

Now, scientists from international research institutions, including Kyoto University, have confirmed that the intrinsic alignments of galaxies have characteristics that allow it to be a powerful probe of dark matter and dark energy on a cosmological scale.

By gathering evidence that the distribution of galaxies more than tens of millions of light years away is subject to the gravitational effects of dark matter, the team succeeded in testing general theory of gravity at vast spatial scales. The international team analyzed the positions and orientations of galaxies, acquired from archived data of 1.2 million galaxy observations. With the help of available 3D positional information of each galaxy, the resulting statistical analysis quantitatively characterized the extent to which the orientation of distant galaxies is aligned.

Wednesday, April 19, 2023

Particle trio exceeds expectations at LHC

Illustration Credit: ATLAS Experiment/CERN

The ATLAS experiment measured more than expected of a trio of particles in the aftermath of proton collisions. The results will refine physicists’ understanding of our universe at the subatomic level.

The ATLAS experiment has confirmed that a trio of particles – a top-antitop quark pair and a W boson –occurs more frequently than expected in the wake of proton-proton collisions inside the Large Hadron Collider (LHC). 

The process that creates these three particles post impact is quite rare: Only one out of every 50,000 collisions at the LHC produces the trio, known as ttW. After popping into existence, top quarks and W bosons are short lived and decay almost immediately, so the team identified ttW events based on the electrons and muons they decay into. 

Members of the ATLAS group at the Department of Energy's SLAC National Accelerator Laboratory have spent the last three years completing a complex analysis to measure the process, including developing novel methods to estimate and remove background and detector effects to maximize the accuracy and detail of the analysis of the measurement. The results will help researchers better test theories of elementary particle physics as well as help experimentalists studying other particle physics processes.

New blue light technique could enable advances in understanding nanoscale technologies

Photo Credit: Courtesy of Brown University

With a new microscopy technique that uses blue light to measure electrons in semiconductors and other nanoscale materials, a team of Brown University researchers is opening a new realm of possibilities in the study of these critical components, which can help power devices like mobile phones and laptops.

The findings are a first in nanoscale imaging and provide a workaround to a longstanding problem that has greatly limited the study of key phenomena in a wide variety of materials that could one day lead to more energy-efficient semiconductors and electronics. The work was published in Light: Science & Applications.

“There is a lot of interest these days in studying materials with nanoscale resolution using optics,” said Daniel Mittleman, a professor in Brown’s School of Engineering and author of the paper describing the work. “As the wavelength gets shorter, this becomes a lot harder to implement. As a result, nobody had ever done it with blue light until now.”

Tuesday, April 18, 2023

Teasing strange matter from the ordinary

New insights from Jefferson Lab reveal details of how strange matter forms in ordinary matter
Photo Credit: Courtesy of Jefferson Lab

In a unique analysis of experimental data, nuclear physicists have made the first-ever observations of how lambda particles, so-called “strange matter,” are produced by a specific process called semi-inclusive deep inelastic scattering (SIDIS). What’s more, these data hint that the building blocks of protons, quarks and gluons, are capable of marching through the atomic nucleus in pairs called diquarks, at least part of the time. These results come from an experiment conducted at the U.S. Department of Energy’s Thomas Jefferson National Accelerator Facility.

It’s a result that has been decades in the making. The dataset was originally collected in 2004. Lamiaa El Fassi, now an associate professor of physics at Mississippi State University and principal investigator of the work, first analyzed these data during her thesis project to earn her graduate degree on a different topic.

Nearly a decade after completing her initial research with these data, El Fassi revisited the dataset and led her group through a careful analysis to yield these unprecedented measurements. The dataset comes from experiments in Jefferson Lab’s Continuous Electron Beam Accelerator Facility (CEBAF), a DOE user facility. In the experiment, nuclear physicists tracked what happened when electrons from CEBAF scatter off the target nucleus and probe the confined quarks inside protons and neutrons. The results were recently published in Physical Review Letters.

The quantum spin liquid that isn't one

Prof. Andrej Pustogow
Photo Credit: Courtesy of TU Wien

The simplest explanation is often the best - this also applies to fundamental science. Researchers from TU Wien and Toho University recently showed that a supposed quantum spin liquid can be described by more conventional physics.

For two decades, it was believed that a possible quantum spin liquid was discovered in a synthetically produced material. In this case, it would not follow the laws of classical physics even on a macroscopic level, but rather those of the quantum world. There is great hope in these materials: they would be suitable for applications in quantum entangled information transmission (quantum cryptography) or even quantum computation.

Now, however, researchers from TU Wien and Toho University in Japan have shown that the promising material, κ-(BEDT-TTF)2Cu2(CN)3, is not the predicted quantum spin liquid, but a material that can be described using known concepts.

In their recent publication in the journal "Nature Communications", the researchers report how they investigated the mysterious quantum state by measuring the electrical resistance in κ-(BEDT-TTF)2Cu2(CN)3 as a function of temperature and pressure. In 2021, Andrej Pustogow from the Institute of Solid-State Physics at TU Wien has already investigated the magnetic properties of this material, opens an external URL in a new window.

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