Physics News and Discussions

[weatheriscool]

Physicists create platform to achieve ultra-strong photon-to-magnon coupling

by National University of Science and Technology MISIS
https://phys.org/news/2021-06-physicist ... pling.html

A team of scientists from NUST MISIS and MIPT have developed and tested a new platform for realization of the ultra-strong photon-to-magnon coupling. The proposed system is on-chip and is based on thin-film hetero-structures with superconducting, ferromagnetic and insulating layers. This discovery solves a problem that has been on the agenda of research teams from different countries for the last 10 years, and opens new opportunities in implementing quantum technologies. The study was published in the highly ranked journal Science Advances.

The last decade has seen significant progress in the development of artificial quantum systems. Scientists are exploring different platforms, each with its own advantages and disadvantages. The next critical step for advancing quantum industry requires an efficient method of information exchange between platform hybrid systems that could benefit from distinct platforms. For example, hybrid systems based on collective spin excitations, or magnons, are being developed. In such systems, magnons must interact with photons, standing electromagnetic waves trapped in a resonator. The main limiting factor for developing such systems is the fundamentally weak interaction between photons and magnons. They are of different sizes, and follow different dispersion laws. This size difference of a hundred times or more considerably complicates the interaction.

[weatheriscool]

Electron-pair discovery advances field of quantum materials
https://phys.org/news/2021-06-electron- ... antum.html
by Linda Glaser, Cornell University

In 2016, physicist J.C. Séamus Davis discovered an elusive state of quantum matter in the cuprates, which are copper oxide materials laced with other atoms. That launched a new sub-field in the study of quantum materials.

But whether this was a unique phenomenon in the cuprates or a universal and important property of nature remained unknown—until now.

Using an improved version of the radically new quantum microscope technology he developed for this purpose, Davis and his team have now found the same exotic state of quantum matter in a widely used and conventional type of material, the transition metal dichalcogenides (TMD).

Their paper, "Discovery of a Cooper-pair Density Wave State in a Transition-metal Dichalcogenide," published June 25 in Science. Co-authors include Cornell postdoctoral fellows Xiaolong Liu and Yi Xue Chong, and Rahul Sharma, Ph.D. '20, a postdoc at the University of Maryland.

[caltrek]

Unless one wants to argue that unidentified aerial phenomenon are a purely psychological phenomena, I think this topic belongs in the physics forum. The U.S. government certainly seems to think so. I thought that Yuli Ban had started a thread in this forum dedicated to this specific topic, by my attempt to locate such a thread using the search function came up empty. I guess that makes it an unidentified posting phenomena.

Audience:

Pentagon Releases UFO Report, Some Phenomena Still Unexplainable
by Jack Rodgers
June 25, 2021

https://www.courthousenews.com/pentagon ... plainable/

Introducing:

(Courthouse News) — A Defense Department program designed to investigate military reports of unidentified aerial phenomena, or UAPs, released its anticipated report Friday finding that the flying objects aren’t aliens, but that it isn’t quite sure what they are.

The Pentagon’s long-awaited assessment does not paint a clear picture of what service members have experienced, nor does it give definitive answers to what the objects may be.

Of the 144 sightings examined by officials as part of the report, only one was identifiable, the report notes.

A handful of those incidents — 18 of those encounters — observers describe the UAPs moving in ways uncharacteristic to present technology.

“Some UAP appeared to remain stationary in winds aloft, move against the wind, maneuver abruptly, or move at considerable speed, without discernable means of propulsion,” the report states. “In a small number of cases, military aircraft systems processed radio frequency (RF) energy associated with UAP sightings.

In the image from video provided by the Department of Defense labeled Gimbal, from 2015, an unexplained object is seen at center as it is tracked as it soars high along the clouds, traveling against the wind.
(Department of Defense via AP)

[weatheriscool]

The first on-chip valley-dependent quantum interference
https://phys.org/news/2021-06-on-chip-v ... antum.html
by University of Science and Technology of China

A research team led by academician Guo Guangcan from University of Science and Technology of China (USTC) of the Chinese Academy of Sciences (CAS), collaborating with researchers from Sun Yat-sen University and Zhejiang University, realized two-photon quantum interference in the structure of valley-dependent topological insulators based on the valley Hall effect.

The study was published in Physical Review Letters on June 11st, 2021.

Topological photonics has a practical application prospect in the research of photonic chips due to its robust energy transport prosperities. The key to topological phase transition is to generate an energy gap at certain degenerate points by breaking either the time-reversal symmetry (TRS) or inversion symmetry.

[weatheriscool]

Physicists observationally confirm Hawking's black hole theorem for the first time

by Jennifer Chu, Massachusetts Institute of Technology
https://phys.org/news/2021-07-physicist ... -hole.html

There are certain rules that even the most extreme objects in the universe must obey. A central law for black holes predicts that the area of their event horizons—the boundary beyond which nothing can ever escape—should never shrink. This law is Hawking's area theorem, named after physicist Stephen Hawking, who derived the theorem in 1971.

Fifty years later, physicists at MIT and elsewhere have now confirmed Hawking's area theorem for the first time, using observations of gravitational waves. Their results appear today in Physical Review Letters.

[weatheriscool]

Scientists propose new source for rare subatomic particles
https://phys.org/news/2021-07-scientist ... icles.html
by Liu Jia, Chinese Academy of Sciences

A paper based on joint research by Prof. Yuan Changzheng from Institute of High Energy Physics of the Chinese Academy of Sciences, and Prof. Marek Karliner from Tel Aviv University of Israel, was published in Physical Review Letters. It points out a new abundant source of antineutrons and hyperons. These rare subatomic particles are essential for studying forces governing the behavior of matter at the smallest distances, from atomic nuclei to neutron stars.

Physicists investigate the subatomic world by bombarding their subjects with a hail of tiny subatomic 'bullets'. Based on how these 'bullets' bounce off their target, one can infer a wealth of detailed information about the target's structure. This method was pioneered by Ernest Rutherford, who used it to discover the atomic nucleus more than 100 years ago.

[weatheriscool]

Physicists take the most detailed image of atoms to date
https://www.sciencemag.org/news/2021/06 ... m=Facebook
By Anil OzaJun. 30, 2021 , 12:20 PM

Physicists just put Apple’s latest iPhone to shame, taking the most detailed image of atoms to date with a device that magnifies images 100 million times, Scientific American reports. The researchers, who set the record for the highest resolution microscope in 2018, outdid themselves with a study published last month. Using a method called electron ptychography, in which a beam of electrons is shot at an object and bounced off to create a scan that algorithms use to reverse engineer the above image, were used to visualize the sample. Previously, scientists could only use this method to image objects that were a few atoms thick. But the new study lays out a technique that can image samples 30 to 50 nanometers wide—a more than 10-fold increase in resolution, they report in Science. The breakthrough could help develop more efficient electronics and batteries, a process that requires visualizing components on the atomic level.

[weatheriscool]

The pressure is off and high temperature superconductivity remains

by Nicole Johnson, University of Houston
https://phys.org/news/2021-07-pressure- ... ivity.html

In a critical next step toward room-temperature superconductivity at ambient pressure, Paul Chu, Founding Director and Chief Scientist at the Texas Center for Superconductivity at the University of Houston (TcSUH), Liangzi Deng, research assistant professor of physics at TcSUH, and their colleagues at TcSUH conceived and developed a pressure-quench (PQ) technique that retains the pressure-enhanced and/or -induced high transition temperature (Tc) phase even after the removal of the applied pressure that generates this phase.

Pengcheng Dai, professor of physics and astronomy at Rice University and his group, and Yanming Ma, Dean of the College of Physics at Jilin University, and his group contributed toward successfully demonstrating the possibility of the pressure-quench technique in a model high temperature superconductor, iron selenide (FeSe). The results were published in the journal Proceedings of the National Academy of Sciences.

[Yuli Ban]

For The First Time, Scientists Have Connected a Superconductor to a Semiconductor
The team behind the research is hoping to open up all kinds of new applications in classical and quantum physics

Scientists have succeeded in combining two exciting material types together for the very first time: an ultrathin semiconductor just a single atom thick; and a superconductor, capable of conducting electricity with zero resistance.

Both these materials have unusual and fascinating properties, and by putting them together through a delicate lab fabrication process, the team behind the research is hoping to open up all kinds of new applications in classical and quantum physics.

Semiconductors are key to the electrical gadgets that dominate our lives, from TVs to phones. What makes them so useful as opposed to regular metals is their electrical conductivity can be adjusted by applying a voltage to them (among other methods), making it easy to switch a current flow on and off.

Here, a single layer of the semiconductor molybdenum disulfide (MoS2) was extracted and added to the fabrication process.

Then we have superconductors – able to transfer an electrical charge with perfect efficiency and nothing lost to heat, when at a certain temperature (usually an extremely low one).

[weatheriscool]

Quantum phase transition discovered in a quasi-2D system consisting purely of spins
https://phys.org/news/2021-07-quantum-p ... urely.html
by José Tadeu Arantes, FAPESP

Pure quantum systems can undergo phase transitions analogous to the classical phase transition between the liquid and gaseous states of water. At the quantum level, however, the particle spins in states that emerge from phase transitions display collective entangled behavior. This unexpected observation offers a new avenue for the production of materials with topological properties that are useful in spintronics applications and quantum computing.

The discovery was made by an international collaboration led by Julio Larrea, a professor at the University of São Paulo's Physics Institute (IF-USP) in Brazil. Larrea is first author of an article on the study published in Nature.

"We obtained the first experimental evidence of a first-order quantum phase transition in a quasi-two-dimensional system consisting entirely of spins. It was a groundbreaking study in terms of both experimental development and theoretical interpretation," Larrea said.

[weatheriscool]

Electrons in quantum liquid gain energy from laser pulses

by Graz University of Technology

The absorption of energy from laser light by free electrons in a liquid has been demonstrated for the first time. Until now, this process was observed only in the gas phase. The findings, led by Graz University of Technology, open new doors for ultra-fast electron microscopy.

The investigation and development of materials crucially depends on the ability to observe smallest objects at fastest time scales. The necessary spatial resolution for investigations in the (sub-)atomic range can be achieved with electron microscopy. For the most rapid processes, however, proceeding within a few femtoseconds (quadrillionths of a second), the time resolution of conventional electron microscopes is insufficient. To improve the time duration of electron pulses, electrons would have to be selected within a shorter time window—in analogy to a camera shutter, which controls the exposure time in photography.

In principle, this temporal selection is possible with extremely short laser pulses through a process called laser-assisted electron scattering (LAES). In this process, electrons can absorb energy from the light field during collisions with atoms of the sample under investigation. "Structural information is provided by all electrons, but those that have a higher energy level can be assigned to the time window in which the light pulse was present. With this method, it is possible to select a short time window from the long electron pulse and thus improve the time resolution," explains Markus Koch, professor at the Institute of Experimental Physics at Graz University of Technology. So far, however, LAES processes have only been observed in the gas phase, despite their investigation for about 50 years.

https://phys.org/news/2021-07-electrons ... nergy.html

[weatheriscool]

The demonstration of ultrafast switching to an insulating-like metastable state

by Ingrid Fadelli , Phys.org
https://phys.org/news/2021-07-ultrafast ... state.html

In recent years, physicists and electronics engineers have been trying to devise strategies to control or produce quantum states of matter in different materials. Such strategies could ultimately prove valuable for the development of new technological devices.

Researchers at the University of Tokyo and UMR 7162 CNRS Universitè Paris recently introduced a new approach to attain the ultrafast switching of materials to an insulating-like metastable state. Their strategy, introduced in a paper published in Nature Physics, is based on the direct excitation of the amplitude mode of a charge density wave (i.e., amplitudon) via the application of an intense terahertz pulse.

"Our primary interest is to control quantum states of matter by light in an ultrafast manner while avoiding the heating effect." Ryo Shimano, one of the researchers who carried out the study, told Phys.org. "In correlated electron materials, multiple quantum phases including superconductivity, density waves and magnetic orders appear next to each other in their phase diagram. We are investigating the potential of light as a tuning knob for these quantum phases."

[Time_Traveller]

Star Trek’s Warp Drive Leads to New Physics

July 13, 2021

For Erik Lentz, it all started with Star Trek. Every few episodes of Star Trek: The Next Generation, Captain Jean-Luc Picard would raise his hand and order, “Warp one, engage!” Then stars became dashes, and light-years flashed by at impossible speed. And Lentz, still in elementary school, wondered whether warp drive might also work in real life.

“At some point, I realized that the technology didn’t exist,” Lentz says. He studied physics at the University of Washington, wrote his Ph.D. dissertation on dark matter and generally became far too busy to be concerned with science fiction. But then, at the start of the coronavirus pandemic, Lentz found himself alone in Göttingen, Germany, where he was doing postdoctoral work. He suddenly had plenty of free time on his hands—and childhood fancies in his head.

Lentz read everything he could find on warp drives in the scientific literature, which was not very much. Then he began to think about it for himself. After a few weeks, something occurred to him that everyone else seemed to have overlooked. Lentz put his idea on paper and discussed it with more experienced colleagues. A year later it was published in a physics journal.

It quickly became clear that Lentz was not the only person dreaming about warp drives. Media outlets all over the world picked up the story, and a dozen journalists asked for interviews. A discussion on the online forum Reddit attracted 2,700 comments and 33,000 likes. One Internet user wrote, “Anyone else feel like they were born 300 years too soon?”

https://www.scientificamerican.com/arti ... w-physics/

[weatheriscool]

Optical levitation of glass nanosphere enables quantum control
https://phys.org/news/2021-07-optical-l ... ables.html
by Oliver Morsch, ETH Zurich

Researchers at ETH Zurich have trapped a tiny sphere measuring a hundred nanometres using laser light and slowed down its motion to the lowest quantum mechanical state. This technique could help researchers to study quantum effects in macroscopic objects and build extremely sensitive sensors.

Why can atoms or elementary particles behave like waves according to quantum physics, which allows them to be in several places at the same time? And why does everything we see around us obviously obey the laws of classical physics, where such a phenomenon is impossible? In recent years, researchers have coaxed larger and larger objects into behaving quantum mechanically. One consequence of this is that, when passing through a double slit, these objects form an interference pattern that is characteristic of waves.

Up to now, this could be achieved with molecules consisting of a few thousand atoms. However, physicists hope one day to be able to observe such quantum effects with properly macroscopic objects. Lukas Novotny, professor of photonics, and his collaborators at the Department of Information Technology and Electrical Engineering at ETH Zurich have now made a crucial step in that direction. Their results were recently published in the scientific journal Nature.

[Yuli Ban]

This Bendable Ice Is Freaking Us Out

New research from China shows that thin, carefully crafted strands of ice can take on surprisingly elastic properties.

As a medium, ice is very unforgiving. It melts at temperatures above freezing (obviously) and snaps instead of bending when under strain. Defects like microcracks, surface imperfections, and pores—which form during the freezing process—give ice its brittle, stubborn quality.

Such is not the case for all ice, however. Scientists in China have shown that ice, under the right circumstances, can be surprisingly flexible and springy. In tests, strands measuring just 4.4 micrometers in diameter could be bent to a near-circular shape, and when the pressure was eased, the strands returned to their original shape. Limin Tong from Zhejiang University in Hangzhou led the new research, published today in Science.

[weatheriscool]

Scientists create world's thinnest magnet
https://phys.org/news/2021-07-scientist ... agnet.html
by Lawrence Berkeley National Laboratory

The development of an ultrathin magnet that operates at room temperature could lead to new applications in computing and electronics—such as high-density, compact spintronic memory devices—and new tools for the study of quantum physics.

The ultrathin magnet, which was recently reported in the journal Nature Communications , could make big advances in next-gen memories, computing, spintronics, and quantum physics. It was discovered by scientists at the Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab) and UC Berkeley.

"We're the first to make a room-temperature 2-D magnet that is chemically stable under ambient conditions," said senior author Jie Yao, a faculty scientist in Berkeley Lab's Materials Sciences Division and associate professor of materials science and engineering at UC Berkeley.

[weatheriscool]

Buzz about thermoelectrics heats up with promising new magnesium-based materials
https://phys.org/news/2021-07-thermoele ... rials.html
by Jeremy Rumsey, Oak Ridge National Laboratory

The landing of NASA's Perseverance rover was another leap forward not only for space exploration but also for the technology that's powering the craft on its years-long mission on Mars—a thermoelectric generator that turns heat into electricity.

Looking for the next leap in thermoelectric technologies, researchers at Duke University and Michigan State University gained new fundamental insights into two magnesium-based materials (Mg3Sb2 and Mg3Bi2) that have the potential to significantly outperform traditional thermoelectric designs and would also be more environmentally friendly and less expensive to manufacture. Contrary to prevailing scientific wisdom regarding the use of heavy elements, the researchers showed that replacing atoms of heavier elements such as calcium and ytterbium with lighter magnesium atoms actually led to a threefold increase in the magnesium-based materials' performance.

[weatheriscool]

ATLAS reports first observation of WWW production
https://phys.org/news/2021-07-atlas-www-production.html
by ATLAS Experiment

The ATLAS Collaboration at CERN announces the first observation of "WWW production": The simultaneous creation of three massive W bosons in high-energy Large Hadron Collider (LHC) collisions.

As a carrier particle of the electroweak force, the W boson plays a crucial role in the Standard Model of particle physics. Though discovered nearly four decades ago, the W boson continues to provide physicists with new avenues for exploration. In particular, its study has allowed scientists to test the Standard Model through precise measurements of rare processes.

Today, at the EPS-HEP Conference 2021, the ATLAS Collaboration announced the first observation of a rare process: The simultaneous production of three W bosons. ATLAS researchers analyzed the full LHC Run-2 dataset, recorded by the detector between 2015 and 2018, to observe the process with a statistical significance of 8.2 standard deviations—well above the 5 standard-deviation threshold needed to claim observation. This result follows an earlier observation by the CMS Collaboration of inclusive three weak boson production.

[weatheriscool]

New exotic matter particle, a tetraquark, discovered
https://phys.org/news/2021-07-exotic-pa ... quark.html
by CERN

Today, the LHCb experiment at CERN is presenting a new discovery at the European Physical Society Conference on High Energy Physics (EPS-HEP). The new particle discovered by LHCb, labeled as Tcc+, is a tetraquark—an exotic hadron containing two quarks and two antiquarks. It is the longest-lived exotic matter particle ever discovered, and the first to contain two heavy quarks and two light antiquarks.

Quarks are the fundamental building blocks from which matter is constructed. They combine to form hadrons, namely baryons, such as the proton and the neutron, which consist of three quarks, and mesons, which are formed as quark-antiquark pairs. In recent years a number of so-called exotic hadrons—particles with four or five quarks, instead of the conventional two or three—have been found. Today's discovery is of a particularly unique exotic hadron, an exotic exotic hadron if you like.

[weatheriscool]

Engineers bend light to enhance wavelength conversion
https://phys.org/news/2021-07-wavelengt ... rsion.html
by University of California, Los Angeles

Schematic of InAs lattice in contact with a nanoantenna array that bends incoming light so it is tightly confined around the shallow surface of the semiconductor. The giant electric field created across the surface of the semiconductor accelerates photo-excited electrons, which then unload the extra energy they gained by radiating it at different optical wavelengths. Credit: Deniz Turan/UCLA

Electrical engineers from the UCLA Samueli School of Engineering have developed a more efficient way of converting light from one wavelength to another, opening the door for improvements in the performance of imaging, sensing and communication systems.

Mona Jarrahi, professor of electrical and computer engineering at UCLA Samueli, led the Nature Communications-published research.

Finding an efficient way to convert wavelengths of light is crucial to the improvement of many imaging and sensing technologies. For example, converting incoming light into terahertz wavelengths enables imaging and sensing in optically opaque environments. However, previous conversion frameworks were inefficient and required bulky and complex optical setups.