Physics News and Discussions

weatheriscool
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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
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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."
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Time_Traveller
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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/
“People assume that time is a strict progression of cause to effect, but *actually* from a non-linear, non-subjective viewpoint - it's more like a big ball of wibbly wobbly... time-y wimey... stuff.” - Steven Moffat
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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.
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Yuli Ban
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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.
And remember my friend, future events such as these will affect you in the future
weatheriscool
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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.
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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.
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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.
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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.
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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.
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