University of Central Florida (UCF) researcher Debashis Chanda, a professor at UCF’s NanoScience Technology Center, has developed a new technique to detect long wave infrared (LWIR) photons of different wavelengths or “colors.”
The research was recently published in Nano Letters.
The new detection and imaging technique will have applications in analyzing materials by their spectral properties, or spectroscopic imaging, as well as thermal imaging applications.
Scientists from Karlsruhe Institute of Technology (KIT) and the Indian Institute of Technology Guwahati (IITG) have developed a surface material that repels water droplets almost completely. Using an entirely innovative process, they changed metal-organic frameworks (MOFs)—artificially designed materials with novel properties—by grafting hydrocarbon chains.
The resulting superhydrophobic (extremely water-repellent) properties are interesting for use as self-cleaning surfaces that need to be robust against environmental influences, such as on automobiles or in architecture. The study was published in the journal Materials Horizons.
MOFs (metal-organic frameworks) are composed of metals and organic linkers that form a network with empty pores resembling a sponge. Their volumetric properties—unfolding two grams of this material would yield the area of a football pitch—make them an interesting material in applications such as gas storage, carbon dioxide separation, or novel medical technologies.
A research team from NIMS and UTokyo has proposed and demonstrated that the transverse magneto-thermoelectric conversion in magnetic materials can be utilized with much higher performance than previously by developing artificial materials comprising alternately and obliquely stacked multilayers of a magnetic metal and semiconductor.
The work is published in the journal Nature Communications.
When a temperature gradient is applied to a magnetic conductor, a charge current is generated in a direction orthogonal to the directions of both temperature gradient and magnetization of the magnetic conductor.
Copper-oxide (CuO2) superconductors, such as Bi2Sr2CaCu2O8+δ (Bi2212), have unusually high critical temperatures. Optical reflectivity measurements of Bi2212 have shown that it exhibits strong optical anisotropy. However, this has not been studied through optical transmittance measurements, which can offer more direct insights into bulk properties.
Now, researchers have elucidated the origin of this optical anisotropy through ultraviolet and visible light transmittance measurements of lead-doped Bi2212 single crystals, enabling a more precise investigation into its superconductivity mechanisms. Their research is published in the journal Scientific Reports.
Superconductors are materials which conduct electricity without any resistance when cooled down below a critical temperature. These materials have transformative applications in various fields, including electric motors, generators, high-speed maglev trains, and magnetic resonance imaging.
Photonic space-time crystals enhance light interaction and amplification, offering new applications in optical information processing.
Photonic space-time crystals are advanced materials designed to enhance the performance and efficiency of technologies like wireless communication and lasers. These crystals have a unique structure that is periodically arranged in three spatial dimensions and also changes over time, allowing precise control of light’s behavior. Researchers from the Karlsruhe Institute of Technology (KIT), in collaboration with Aalto University, the University of Eastern Finland, and Harbin Engineering University in China, have demonstrated how these four-dimensional materials can be applied in real-world technologies. Their findings were published in Nature Photonics.
Photonic Time Crystals
Theory of quantum anomalous Hall phases in pentalayer rhombohedral graphene moiré structures https://arxiv.org/abs/2311.
MIT physicists surprised to discover electrons in pentalayer graphene can exhibit fractional charge.
New theoretical research from MIT physicists explains how it could work, suggesting that electron interactions in confined two-dimensional spaces lead to novel quantum states, independent of magnetic fields.
Groundbreaking Discovery in Graphene
MIT physicists have made significant progress in understanding how electrons can split into fractional charges. Their findings reveal the conditions that create exotic electronic states in graphene and other two-dimensional materials.
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).
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.”
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 beam energy, but also produces high-quality beam at this energy level for the first time, paving the way for future high-efficiency machines.
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.