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Category: particle physics – Page 366

Precision Spectroscopy Now Possible Under Starved-Light Conditions

In a study recently published in Nature, researchers from the Max Born Institute in Berlin, Germany, and the Max-Planck Institute of Quantum Optics in Garching have unveiled a new technique for deciphering the properties of matter with light, that can simultaneously detect and precisely quantify many substances with a high chemical selectivity.

Their technique interrogates the atoms and molecules in the ultraviolet spectral region at very feeble light levels. Using two optical frequency combs and a photon counter, the experiments open up exciting prospects for conducting dual-comb spectroscopy in low-light conditions and they pave the way for novel applications of photon-level diagnostics, such as precision spectroscopy of single atoms or molecules for fundamental tests of physics and ultraviolet photochemistry in the Earth’s atmosphere or from space telescopes.

Ghost particle on the scales: Research offers more precise determination of neutrino mass

What is the mass of a neutrino at rest? This is one of the big unanswered questions in physics. Neutrinos play a central role in nature. A team led by Klaus Blaum, Director at the Max Planck Institute for Nuclear Physics in Heidelberg, has now made an important contribution in “weighing” neutrinos as part of the international ECHo collaboration. Their findings are published in Nature Physics.

Using a Penning trap, it has measured the change in mass of a holmium-163 isotope with extreme precision when its nucleus captures an electron and turns into dysprosium-163. From this, it was able to determine the Q value 50 times more accurately than before. Using a more precise Q-value, possible systematic errors in the determination of the neutrino mass can be revealed.

In the 1930s, it turned out that neither the energy nor the momentum balance is correct in the radioactive beta decay of an atomic nucleus. This led to the postulate of “ghost particles” that “secretly” carry away energy and momentum. In 1956, experimental proof of such neutrinos was finally obtained. The challenge: neutrinos only interact with other particles of matter via the weak interaction that is also underlying the beta decay of an atomic nucleus.

School on Quantum Chaos

Quantum chaos focuses on the quantum manifestations of classical chaos. A characteristic of classical chaos is the exponential sensitivity of the dynamics with respect to infinitesimal changes in the initial conditions. Thus, to classify classical dynamics it is sufficient to follow phase space trajectories starting infinitesimally close to each other and to determine the evolution of their distances with respect to each other with time. Because of the uncertainty relation, this is no longer possible in the corresponding quantum system. One important aspect of quantum chaos is the understanding of features of the classical dynamics in terms of the fluctuation properties in the energy spectra of closed quantum systems or of the fluctuations exhibited by the scattering matrix elements describing open ones. The fluctuation properties are predicted to be universal, that is, to be the same for systems belonging to the same universality class and exhibiting the same chaotic behavior in the corresponding classical dynamics and to be describable by random matrix theory. Furthermore, random-matrix models that had been developed for the scattering matrix associated with compound-nuclear reactions have been shown to be applicable to quantum-chaotic scattering processes. A second important aspect within the field of quantum chaos concerns the semiclassical approach. In this context, one of the most important achievements was the periodic orbit theory pioneered by Gutzwiller, which led to understanding the impact of the classical dynamics on the properties of the quantum system in terms of purely classical quantities. The focus of research within the field of quantum chaos has been extended to relativistic quantum systems and to many-body quantum systems with focus on random matrix theory and the semiclassical approach. In distinction to single-particle systems, many-body systems like atomic nuclei do not have a classical analogue. In recent years different measures of chaos and models have been developed. Here, a prominent model is the Sachdev-Ye-Kitaev model which serves as a paradigm for the study of quantum chaos in strongly interacting many-body systems. The school is aimed at PhD students, post-docs and outstanding master students and the first part will provide a survey of single-and many-body quantum chaos and applications based on random-matrix theory and the semiclassical approach. The second part of the school will focus on current aspects of research in the context of many-body quantum chaos. There is no registration fee and limited funds are available for travel and local expenses. Organizers: Hilda Cerdeira (IFT-UNESP, Brazil) Barbara Dietz-Pilatus (Institute for Basic Science (IBS), Republic of Korea)

Graphene’s Light-Speed Electrons Promise Revolution in Nanoscale Transistors

Researchers have shown that double-layer graphene can function both as a superconductor and an insulator, a property that could revolutionize transistor technology. This dual functionality allows for the development of nanoscale transistors that are highly energy-efficient.

An international research team led by the University of Göttingen has demonstrated experimentally that electrons in naturally occurring double-layer graphene move like particles without any mass, in the same way that light travels. Furthermore, they have shown that the current can be “switched” on and off, which has potential for developing tiny, energy-efficient transistors – like the light switch in your house but at a nanoscale. The Massachusetts Institute of Technology (MIT), USA, and the National Institute for Materials Science (NIMS), Japan, were also involved in the research. The results were published in the scientific journal Nature Communications.

Researchers Develop “Goldene” — A New Form of Ultra-Thin Gold With Semiconductor Properties

For the first time, scientists have managed to create sheets of gold only a single atom layer thick. The material has been termed goldene. According to researchers from Linköping University, Sweden, this has given the gold new properties that can make it suitable for use in applications such as carbon dioxide conversion, hydrogen production, and production of value-added chemicals. Their findings are published in the journal Nature Synthesis.

Scientists have long tried to make single-atom-thick sheets of gold but failed because the metal’s tendency to lump together. But researchers from Linköping University have now succeeded thanks to a hundred-year-old method used by Japanese smiths.

“If you make a material extremely thin, something extraordinary happens – as with graphene. The same thing happens with gold. As you know, gold is usually a metal, but if single-atom-layer thick, the gold can become a semiconductor instead,” says Shun Kashiwaya, researcher at the Materials Design Division at Linköping University.