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Category: particle physics – Page 312

Ever since its discovery in 2004, graphene has received attention owing to its extraordinary properties, among them its extremely high carrier mobility. However, the high carrier mobility has only been observed using techniques that require complex and expensive fabrication methods. Now, researchers at Chalmers report on a surprisingly high charge-carrier mobility of graphene using much cheaper and simpler methods.

“This finding shows that graphene transferred to cheap and flexible substrates can still have an uncompromisingly high mobility, and it paves the way for a new era of graphene nano-electronics,” says Munis Khan, researcher at Chalmers University of Technology.

Graphene is the one-atom-thick layer of carbon atoms, known as the world’s thinnest material. The material has become a popular choice in semiconductor, automotive and optoelectronic industry due to its excellent electrical, chemical, and material properties. One such property is its extremely .

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Dude, what if everything around us was just … a hologram?

The thing is, it could be—and a University of Michigan physicist is using quantum computing and machine learning to better understand the idea, called holographic duality.

Holographic duality is a mathematical conjecture that connects theories of particles and their interactions with the theory of gravity. This conjecture suggests that the theory of gravity and the theory of particles are mathematically equivalent: what happens mathematically in the theory of gravity happens in the theory of particles, and vice versa.

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A team of researchers working at Tsinghua University in China has created a sub-1-nm gate in a MoS2 transistor. In their paper published in the journal Nature, the group outlines how they created the super tiny gate and explains why they believe it will be difficult for anyone to beat their record.

For most of the history of microcomputing, Moore’s Law has held up—researchers and engineers have managed to double the speed and capability of computers regularly by reducing the size of their components. But more recently, it has grown increasingly difficult to make components smaller as scientists now run into . In this new effort, the researchers believe they may have bumped up against the ultimate limit—they have built a gate that is just one atom in length.

At their most basic, transistors are a source and a drain, with a gate controlling the flow of electricity between them. It switches on and off depending on how much electricity is applied. The push to reduce the size of the components has led to the testing of materials such as carbon nanotubes, which are approximately 1nm, for use as gates. In this new effort, the researchers have unrolled the and used its graphene edge as the gate—reducing its length to just 0.34 nm.

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Probability of a reaction occurring increases 100-fold and points to quantum control of chemistry.

A new step towards quantum control of chemistry has been achieved by researchers in the US, who found that tuning the magnetic field applied to colliding ultracold molecules could alter the probability of them reacting or undergoing inelastic scattering a 100-fold.1 The work could potentially prove useful for producing large ensembles of molecules in the same state and investigating their properties.

At room temperature, the random thermal motion of atoms and molecules blurs the quantum nature of chemistry. In an ultracold regime, however, this thermal motion is stilled, revealing chemical interactions as quantum interference processes between matter waves. Remarkable phenomena have been seen in ultracold atomic gases, such as the creation of Bose–Einstein condensates, in which atoms all enter the quantum ground state of a trap, allowing a macroscopic view of their quantum wavefunction. Wolfgang Ketterle at the Massachusetts Institute of Technology (MIT), whose group performed the new research, shared the 2001 physics Nobel prize for the creation of this condensate.

Cooling molecules to the ground state of a trap is much trickier than cooling atoms because they can contain thermal energy in so many internal degrees of freedom, and was only achieved by Jun Ye of JILA in the US and colleagues recently.2 In 2020, Ye’s group applied an electric field to potassium–rubidium molecules, which decay into diatomic potassium and rubidium molecules. The researchers showed that, at a specific field, the molecules were excited into states forbidden by quantum mechanics and could get close enough to react. This drastically slowed the decay rate. ‘For our system, we typically think that, if the two molecules get very close together, there is close to a 100% chance that they will undergo a chemical reaction,’ explains Kyle Matsuda, Ye’s PhD student and the 2020 paper’s lead author.

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Since the discovery of the Higgs boson a decade ago, the ATLAS and CMS collaborations at the Large Hadron Collider (LHC) have been hard at work trying to unlock the secrets of this special particle. In particular, the collaborations have been investigating in detail how the Higgs boson interacts with fundamental particles such as the particles that make up matter, quarks and leptons. In the Standard Model of particle physics, these matter particles fall into three “generations” of increasing mass, and the Higgs boson interacts with them with a strength that is proportional to their mass. Any deviation from this behavior would provide a clear indication of new phenomena.

ATLAS and CMS have previously observed the interactions of the Higgs boson with the heaviest and leptons, of the third generation, which within the current measurement precision agree with the predictions from the Standard Model. And they have also obtained the first indications that the Higgs boson interacts with a muon, a lepton of the second generation. However, they have yet to observe it interacting with second-generation quarks. In two recent publications, ATLAS and CMS report analyses that place tight limits on the strength of the Higgs boson interaction with a charm quark, a second-generation quark.

ATLAS and CMS studied the Higgs boson interactions by looking at how the boson transforms, or “decays,” into lighter particles or how it is produced together with other particles. In their latest studies, using data from the second run of the LHC, the two teams searched for the decay of the Higgs boson into a charm quark and its antimatter counterpart, the charm antiquark.

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A team of researchers from Lawrence Livermore National Laboratory, the University of California at Berkeley and Princeton University has developed plasma-based techniques to build a lens for laser beams with petawatt-scale power. In their paper published in the journal Physical Review Letters, the group describes the two techniques they developed.

Physicists conducting work with and fusion research efforts are hopeful that other researchers will build lasers that are more powerful than those currently available. Such work has been held up by the solid-state optics technology used to create lasers—giving them more power would damage the parts used to generate the laser, making them useless. In this new effort, the researchers noted that other researchers have found that plasma can be used to create optic components such as amplifiers and mirrors. They wondered if the same might be true for the kind of lens needed to produce extremely powerful laser beams. They came up with a concept that involved inducing patterns of high and in a given plasma. Light moving through it, they note, would experience a based on the density of the plasma.

The researchers did not actually build such a laser, but instead, proposed two ways that it might be built. The first method involved firing two pump lasers at a gas sample. The first laser ionized the gas into a plasma, while the second did not. The result was a plasma with a bulls-eye configuration of high and low-density plasma rings, which could be used as a laser lens.

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Many people say that Einstein failed because he was simply ahead of his time. The knowledge and tools needed to complete a unified theory simply hadn’t been developed before Einstein died in 1955.

Today, many physicists are taking up his quest. The most promising approach appears to be string theory, which requires 10 or more dimensions and describes all elementary particles as vibrating strings, with different modes of vibration producing different particles.

String theory has not yet made any testable predictions, and some scientists worry that string theorists have, like Einstein in his later years, strayed too far from physical reality in their obsession with beautiful mathematics. But many others believe string theory does indeed hold the key to completing Einstein’s quest, and researchers are hoping to find ways to test some of the predictions of string theory.

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Scientists from Durham University and Kings College London have presented a theoretical review in a new study strongly supporting the search for axion dark matter.

The identity of dark matter, which makes up 85% of the matter in the universe, is one of the big unanswered questions in particle physics.

Scientists know of its existence because of its gravitational pull effects on stars and galaxies but what kind of particle it is, still remains a mystery.

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