Phys.org May 4, 2022 An international team of researchers (USA – City College of New York, Virginia Tech, Oak Ridge National Laboratory, City University of New York, Poland) invented a new facile and powerful technique that uses ionic hydrogen to reduce charge carrier density in the bulk of 3D topological insulators and magnets. It made robust non-dissipative surface or edge quantum conduction channels accessible for manipulation and control. Hydrogen-tuning technique of chalcogen-based topological materials and nanostructures uses insertion and extraction of ionic hydrogen from dilute aqueous hydrochloric acid solution, which leaves the layered topological crystal structure as well as electronic […]
Nanoclusters self-organize into centimeter-scale hierarchical assemblies
Phys.org April 22, 2022 An international team of researchers (USA – Cornell University, Rochester Institute of Technology, Canada) has created synthetic nanoclusters from an organic–inorganic mesophase composed of monodisperse Cd37S18 magic-size cluster building blocks. The process produced “magic-size clusters” of 57 atoms, about 1.5 nanometers in length. Each of these nanoparticles had a shell of ligands that could interact with each other in such a way that they formed filaments several microns long and hundreds of nanometers wide. The filaments were periodically decorated with the magic-size clusters with perfect spacing between them. Enhanced patterning was achieved by controlling processing conditions, […]
A new strategy for active metasurface design provides a full 360-degree phase tunable metasurface
Phys.org May 2, 2022 Active metasurfaces have been proposed as one attractive means of achieving high-resolution spatiotemporal control of optical wavefronts, having applications such as LIDAR and dynamic holography. An international team of researchers (South Korea, USA – University of Wisconsin) has developed an electrically tunable metasurface design strategy that operates near the avoided crossing of two resonances, one a spectrally narrow, over-coupled resonance and the other with a high resonance frequency tunability. It displayed an upper limit of 4π range of dynamic phase modulation with no significant variations in optical amplitude, by enhancing the phase tunability through utilizing two […]
Perovskite photovoltaics for a greener Internet-of-Things
Nanowerk April 28, 2022 An international team of researchers (UK, USA – City College of New York) reviewed the novel device concepts that comprise photovoltaic cells alone or in tandem with batteries or supercapacitors, acting as the main power supply to another microelectronic component, enabling self-powered electronics for the Internet of Things (IoT). They emphasize the specific requirements posed by such applications to pave the way to large scale commercialization. They highlighted the importance of supporting a greener IoT ecosystem by eliminating toxic materials and solvents in the device fabrication process…read more. Open Access TECHNICAL ARTICLE
Photons can enable real-time physical random bit generation for information security app
Phys.org May 6, 2022 Most optical-chaos-based random bit generators perform their quantization process in the electrical domain using electrical analog-to-digital converters, so their real-time rates in a single channel are severely limited at the level of Gb/s due to the electronic bottleneck. An international team of researchers (China, UK) has experimentally demonstrated an all-optical method for random bit generation where chaotic pulses are quantized into a physical random bit stream in the all-optical domain by means of a length of highly nonlinear fiber. Using their method, they generated a 10-Gb/s random bit stream on-line. The single-channel real-time rate is limited […]
Physicists Developed a Superconductor Circuit Long Thought to Be Impossible
Science Alert April 27, 2022 An international team of researchers (Germany, China, the Netherlands, USA – Johns Hopkins University) fabricated an inversion symmetry breaking van der Waals heterostructure of NbSe2/Nb3Br8/NbSe2. They demonstrated that even without a magnetic field, the junction can be superconducting with a positive current while being resistive with a negative current. The ΔIc behaviour (the difference between positive and negative critical currents) with magnetic field is symmetric and Josephson coupling was proved through the Fraunhofer pattern. They achieved stable half-wave rectification of a square-wave excitation with a very low switching current density, high rectification ratio and high […]
Team demonstrates rare form of electricity in ultra-thin material
Phys.org April 27, 2022 Molybdenum disulfide (MoS2) is known as one of the most promising and robust 2D electronic materials. However, despite theoretical predictions, no ferroelectricity has been experimentally detected in MoS2. An international team of researchers (USA – University of Nebraska, industry, China, France, Luxembourg) has reported the experimental observation of a stable room-temperature out-of-plane polarization ordering in 2D MoS2 layers, where polarization switching is realized by mechanical pressure induced by a tip of a scanning probe microscope. Using this approach, they created the bi-domain polarization states, which exhibit different piezoelectric activity, second harmonic generation, surface potential, and conductivity. […]
Thin quantum wires work better with less insulating coatings
Phys.org May 4, 2022 Thin semiconducting wires, referred to as quantum wires, are often coated in insulating materials. Previous studies have explored how the mismatch between the insulating properties of both materials can influence their performance. Researchers in Vietnam have shown that thinner wires with less insulating coatings can improve the mobility of the electrons they carry. Previous models have presented conflicting conclusions about the ability of electrons to move through the wire, depending on whether coatings are more or less insulating than the semiconductor. The researchers considered the case where electrons are allowed to cross the outer boundary of […]
A simpler approach for creating quantum materials
Phys.org May 4, 2022 Using twisted bilayer graphene to make devices remains challenging because of the low yield of fabricating twisted bilayer graphene. Researchers at the University of Pennsylvania have shown how patterned, periodic deformations of a single layer of graphene transforms it into a material with electronic properties previously seen in twisted graphene bilayers. To better understand the quantum geometrical properties of this system, they set out to understand the theory underlying how electrons move in this single-layered system. After running computer simulations of single-layered experiments, the researchers were surprised to find new evidence of unexpected phenomena along the […]
Zero-index metamaterials offer new insights into the foundations of quantum mechanics
Phys.org April 27, 2022 Most theoretical derivations of fundamental radiative processes rely on energetic considerations and detailed balance equations, but not on momentum considerations. An international team of researchers (USA – Harvard University, University of Pennsylvania, Belgium, Spain, Denmark) re-examined the foundations of quantum physics from the perspective of momentum and explored what happens when the momentum of light is reduced to zero. They theoretically demonstrated that momentum recoil, transfer momentum from the field to the atom and Doppler shift are inhibited in NZI materials. Fundamental radiative processes inhibition is also explained due to those momentum considerations inside three-dimensional NZI […]