Science Daily May 24, 2022 Key applications such as THz scanning tunnelling microscopy or electronic devices operating at optical clock rates call for ultimately short, almost unipolar waveforms, at megahertz (MHz) repetition rates. An international team of researchers (Germany, USA – University of Michigan) has developed a flexible and scalable scheme for the generation of strong phase-locked THz pulses based on shift currents in type-II-aligned epitaxial semiconductor heterostructures. The measured THz waveforms exhibit only 0.45 optical cycles at their centre frequency within the full width at half maximum of the intensity envelope, peak fields above 1.1 kV cm−1 and spectral components up […]
Explosions help probe elusive atmospheric waves
Phys.org May 25, 2022 Researchers from the Southern Methodist University will discuss a method for using infrasound pulses from detonated munitions to probe atmospheric phenomena at the 182nd Meeting of the Acoustical Society of America meeting. The sound they record propagates upward into the atmosphere and is refracted back down to the ground. The information they provide on the upper atmosphere can tell us about the winds aloft, and these can affect the weather at the ground. However, it requires sizeable source to have enough strength to reach the atmosphere and bounce back. Therefore, they set up detectors in the […]
Generating ultra-violet lasers with near-infrared light through ‘domino upconversion’ of nanoparticles
Phys.org May 19, 2022 Direct ultraviolet lasing is constrained by the fabrication challenge and operation cost. Researchers in China have developed a strategy for the indirect generation of deep-ultraviolet lasing through a tandem upconversion process. They developed a core–shell–shell nanoparticle to achieve deep-ultraviolet emission at 290 nm by excitation in the telecommunication wavelength range at 1550 nm. The ultra large anti-Stokes shift of 1260 nm (~3.5 eV) stems from a tandem combination of distinct upconversion processes that are integrated into separate layers of the core–shell–shell structure. By incorporating the core–shell–shell nanoparticles as gain media into a toroid microcavity, single-mode lasing at 289.2 nm was realized […]
Is it topological? A new materials database has the answer
MIT News May 19, 2022 The recently introduced theories of topological quantum chemistry and symmetry-based indicators (SIs) have facilitated the discovery of topological phases of matter and large-scale searches for materials with experimentally accessible topological properties at the Fermi energy (EF). Away from EF, energetically isolated bands and topological gaps are also useful in numerous experimental settings; they can be accessed via (electro)chemical doping, electrostatic gating, hydrostatic pressure, and nonequilibrium photoexcitation and are relevant to Floquet engineering and nonlinear optical experiments. An international team of researchers (Spain, USA – MIT, Princeton University, Germany) has completed a catalog of stable and […]
The limits of vision: Seeing shadows in the dark
Science Daily May 23, 2022 Mice use a specific neural pathway to detect shadows, and it can detect just about the dimmest shadows possible. The human eye has the same neural circuit, which researchers in Finland think could be used to probe visual diseases at unprecedented resolution. To test shadow detection, the researchers put mice in a maze with nearly no light. The exit was marked by a black spot, just barely distinct from the surrounding darkness. By tracking how the mice moved through the maze and measuring the activity of neurons at the back of the eye the team […]
Long-hypothesized ‘next generation wonder material’ created
Science Daily May 21, 2022 Scientists have long been interested in the construction of new or novel carbon allotropes. The most well-known carbon allotropes are graphite and diamonds, which are created out of sp2 carbon and sp3 carbon, respectively. However, the traditional methods don’t allow for the different types of carbon to be synthesized together in large capacity. Researchers at the University of Colorado used alkyne metathesis as well as thermodynamics and kinetic control to successfully create a material that could rival the conductivity of graphene but with control. Now the team is looking into the details of it, including […]
Nuclear Fusion Can Unleash Even More Power Than We Realized, Scientists Say
Science Alert May 26, 2022 The research led by physicists from the Swiss Plasma Center has determined that the maximum hydrogen fuel density is about twice the Greenwald Limit – an estimate derived from experiments more than 30 years ago. The exact value depends on the power. But as a rough estimate, the increase is on the order of a factor of two in ITER. Although scientists had long suspected the Greenwald Limit could be improved upon, it has been a foundational rule of fusion research for more than 30 years, a guiding principle of the ITER design. The key […]
Release of two new datasets related to climate in Central Asia
Phys.org May 23, 2022 Researchers in China have derived a high-resolution (9 km) climate projection dataset over Central Asia (HCPD-CA) from dynamically downscaled results based on multiple bias-corrected global climate models. It contains four geostatic variables and 10 meteorological elements that are widely used to drive ecological and hydrological models. The reference and future periods are 1986–2005 and 2031–2050, respectively. The carbon emission scenario is Representative Concentration Pathway (RCP) 4.5. The evaluation showed that the data product has good quality in describing the climatology of all the elements in CA despite some systematic biases. Main features of projected climate changes over […]
Researchers demonstrate organic crystals can serve as energy converters for emerging technologies
Phys.org May 20, 2022 While organic crystals were previously thought to be fragile, an international team of researchers (UAE, USA – New York University) has discovered that some organic crystals are mechanically very robust. They demonstrated that the ferroelectric crystals of guanidinium nitrate exert a linear stroke of 51%, the highest value observed when transitioning at 295–305 K on heating and at 265–275 K on cooling. Their maximum force density is higher than electric cylinders, ceramic piezo actuators, and electrostatic actuators, and their work capacity is close to that of thermal actuators. They demonstrated that the material expanded and contracted over half […]
Secure communication with light particles that sidesteps the reliance on polarization
Phys.org May 25, 2022 Researchers in Germany have created a scalable star-shaped quantum-key-distribution (QKD) optical-fiber network using WDM of broadband photon pairs to establish key exchange between multiple pairs of participants. They demonstrated simultaneous bipartite key exchange between any possible combination of participants and showed that the quantum bit error rate (QBER) itself can be used to stabilize the phase in the interferometers by small temperature adjustments. The key distribution is insensitive to polarization fluctuations in the network, enabling key distribution using deployed fibers even under challenging environmental conditions. They demonstrated that the network could be extended to 34 participants […]