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Category: materials – Page 9

The size and strength of the momentum bandgap improve as the quality factor of the metasurface increases. Figure 3f shows that metasurfaces with a higher Q-factor provide wider momentum bandgaps for surface waves with larger amplification rates, assuming the same modulation function. In comparison, the metasurface discussed in Fig. 3b–e has a quality factor of Q = 2.44. Moreover, for sufficiently large Q-factors (Q ≥ 9.75), a second momentum bandgap opens inside the light cone, that is, for propagating waves. The size of the second bandgap grows with the quality factor of the metasurface because resonances with longer lifetimes suffer from smaller radiation losses and require weaker modulation to maintain the same amplification rate. When the quality factor takes sufficiently large values, the two bandgaps merge and the metasurface can amplify incident waves with all possible momenta k ∣ ∣ (see Fig. 3f).

We place a dipole emitter above the metasurface to demonstrate this infinite momentum bandgap (see Fig. 3g). The dipole radiation includes a wide spectrum of momenta, as shown in the upper panel of the figure. Once the temporal modulation of the metasurface is on, waves with all different momenta are amplified and radiated in the specular and retro-directions with respect to the source; see the lower panel in Fig. 3g. This leads to interesting possibilities such as amplified emission and lasing of light from a radiation source6. In contrast to the idea suggested in ref. 6, due to the substantially enhanced bandgap, it is possible here to amplify emission with a large and, in principle, tunable spectrum of wavenumbers. This provides opportunities for beam shaping of the amplified signal and for creating perfect lenses31. Indeed, the evanescent wave content of the source radiation can be reconstructed effectively thanks to the amplification of the wide range of k ∣ ∣. In Supplementary Section 5, we demonstrate that evanescent and propagating wave components of the radiating dipole are amplified by the metasurface in reflection and transmission regimes.

To provide a feasible optical realization of the resonant PTC, we consider a penetrable metasurface surrounded by air and consisting of dielectric nanospheres that are made of a material with a time-varying permittivity (see Fig. 4a). Each nanosphere effectively behaves as an LC resonator as it supports Mie resonances32. For simplicity, we initially ignore material dispersion. The permittivity associated with each nanosphere reads \(\varepsilon (t)=1+{\chi }_{0}[1+m\cos ({\omega }_{{\rm{m}}}t)]\). Varying the permittivity in time modulates the Mie resonance frequencies of the nanospheres (see Fig. 2b). In the following, we rely on the T-matrix method to study the optical response from such a metasurface33 (see Methods and Supplementary Section 6 for details).

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Scientists have accidentally discovered a particle that has mass when it’s traveling in one direction, but no mass while traveling in a different direction. Known as semi-Dirac fermions, particles with this bizarre behavior were first predicted 16 years ago.

The discovery was made in a semi-metal material called ZrSiS, made up of zirconium, silicon and sulfur, while studying the properties of quasiparticles. These emerge from the collective behavior of many particles within a solid material.

“This was totally unexpected,” said Yinming Shao, lead author on the study. “We weren’t even looking for a semi-Dirac fermion when we started working with this material, but we were seeing signatures we didn’t understand – and it turns out we had made the first observation of these wild quasiparticles that sometimes move like they have mass and sometimes move like they have none.”

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Scientists have used a pair of lasers and a supersonic sheet of gas to accelerate electrons to high energies in less than a foot. The development marks a major step forward in laser-plasma acceleration, a promising method for making compact, high-energy particle accelerators that could have applications in particle physics, medicine, and materials science.

In a new study soon to be published in the journal Physical Review Letters, a team of researchers successfully accelerated high-quality beams of electrons to more than 10 billion electronvolts (10 gigaelectronvolts, or GeV) in 30 centimeters. The preprint can be found in the online repository arXiv.

The work was led by the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab), with collaborators at the University of Maryland. The research took place at the Berkeley Lab Laser Accelerator Center (BELLA), which set a world record of 8-GeV electrons in 20 centimeters in 2019. The new experiment not only increases the , but also produces high-quality beam at this energy level for the first time, paving the way for future high-efficiency machines.

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A self-replicating machine is a type of autonomous robot that is capable of reproducing itself autonomously using raw materials found in the environment, thus exhibiting self-replication in a way analogous to that found in nature. Homer Jacobson, Edward F. Moore, Freeman Dyson, John von Neumann, Konrad Zuse and in more recent times by K. Eric Drexler in his book on nanotechnology, Engines of Creation (coining the term clanking replicator for such machines) and by Robert Freitas and Ralph Merkle in their review Kinematic Self-Replicating Machinesmoons and asteroid belts for ore and other materials, the creation of lunar factories, and even the construction of solar power satellites in space. The von Neumann probeuniversal constructor, a self-replicating machine that would be able to evolve and which he formalized in a cellular automata environment. Notably, Von Neumann’s Self-Reproducing Automata scheme posited that open-ended evolution requires inherited information to be copied and passed to offspring separately from the self-replicating machine, an insight that preceded the discovery of the structure of the DNA molecule by Watson and Crick and how it is separately translated and replicated in the cell.https://en.m.wikipedia.org/wiki/Self-replicating_machine#:~:...n_probe_is, [ 9 ] A self-replicating machine is an artificial self-replicating system that relies on conventional large-scale technology and automation. The concept, first proposed by Von Neumann no later than the 1940s, has attracted a range of different approaches involving various types of technology. Certain idiosyncratic terms are occasionally found in the literature. For example, the term clanking replicator was once used by Drexler [ 10 ] to distinguish macroscale replicating systems from the microscopic nanorobots or “assemblers” that nanotechnology may make possible, but the term is informal and is rarely used by others in popular or technical discussions. Replicators have also been called “von Neumann machines” after John von Neumann, who first rigorously studied the idea.

The semiconductor industry’s long held imperative—Moore’s Law, which dictates that transistor densities on a chip should double roughly every two years—is getting more and more difficult to maintain. The ability to shrink down transistors, and the interconnects between them, is hitting some basic physical limitations. In particular, when copper interconnects are scaled down, their resistivity skyrockets, which decreases how much information they can carry and increases their energy draw.

The industry has been looking for alternative interconnect materials to prolong the march of Moore’s Law a bit longer. Graphene is a very attractive optionin many ways: The sheet-thin carbon material offers excellent electrical and thermal conductivity, and is stronger than diamond.

However, researchers have struggled to incorporate graphene into mainstream computing applications for two main reasons. First, depositing graphene requires high temperatures that are incompatible with traditional CMOS manufacturing. And second, the charge carrier density of undoped, macroscopic graphene sheets is relatively low.

Making smaller transistors, and the interconnections between them, is getting near impossible. Copper interconnects get more resistive as they are scaled down, making them worse and slower at carrying information. Startup Destination 2D thinks graphene is the solution. They have a novel technique of growing graphene that is CMOS compatible, promising 100x current density improvement over copper.

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A new study by Rice University physicist Qimiao Si unravels the enigmatic behaviors of quantum critical metals—materials that defy conventional physics at low temperatures. Published in Nature Physics Dec. 9, the research examines quantum critical points (QCPs), where materials teeter on the edge between two distinct phases, such as magnetism and nonmagnetism. The findings illuminate the peculiarities of these metals and provide a deeper understanding of high-temperature superconductors, which conduct electricity without resistance at relatively high temperatures.

Key to this study is , a delicate state where the material becomes ultrasensitive to quantum fluctuations—microscopic disturbances that alter electron behavior. While ordinary metals obey well-established principles, quantum critical metals defy these norms, exhibiting strange and collective properties that have long puzzled scientists. Physicists call such systems “strange metals.”

“Our work dives into how quasiparticles lose their identity in strange metals at these quantum critical points, which leads to unique properties that defy traditional theories,” said Si, the Harry C. and Olga K. Wiess Professor of Physics and Astronomy and director of Rice’s Extreme Quantum Materials Alliance.

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Intel Foundry has showcased “breakthrough” developments in the realm of transistor and packaging technologies, revealing material and silicon innovation.

Intel Foundry Showcases “Subtractive Ruthenium” & New Transistor Technologies To Ensure Node Scalability

[Press Release]: Today at the IEEE International Electron Devices Meeting (IEDM) 2024, Intel Foundry unveiled breakthroughs to help drive the semiconductor industry forward into the next decade and beyond. Intel Foundry showcased new material advancements that help improve interconnections within a chip, resulting in up to 25% capacitance by using subtractive ruthenium.

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MXenes in grooved plastic create durable, heat-tolerant films that twist light beams.

A team of researchers at the University of Michigan employed MXenes, a type of ceramic-like material derived from industrial waste materials to develop heat-tolerant films capable of twisting light beams.

The MXenes were integrated into plastic sheets with microscopic grooves to create sturdy, heat-tolerant films capable of twisting light beams.

This innovation paves the way for imaging applications, such as capturing the hot turbulence of aircraft propulsion systems, helping aerospace engineers improve engine designs for better performance.

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