EurekAlert December 23, 2019 The experimental set-up used by an international team of researchers (Germany, Spain, France, Luxembourg) involved nanoscale gold antennae as well as an ultrafast laser capable of emitting one hundred million single-cycle light pulses per second in order to generate a measurable current. The bowtie design of the optical antenna allowed for a sub-wavelength and sub-cycle spatio-temporal concentration of the electric field of the laser pulse into the gap of a width of six nm. As a result of the highly nonlinear character of electron tunneling out of the metal and acceleration over the gap in the […]
A fast and inexpensive device to capture and identify viruses
EurekAlert December 23, 2019 Currently, virologists estimate that 1.67 million unknown viruses are in animals, a number of which can be transmitted to humans. A team of researchers in the US (Pennsylvania State University, New York University) synthesized a gradient of aligned carbon nanotube forest arrays to capture different viruses and detect them in-situ Raman spectroscopy to identify the viruses based on their individual vibration. They designed and assembled a portable platform that enriches virus particles from several milliliters of clinical samples in a couple of minutes. They added gold nanoparticles to enhance the Raman signal to detect the virus […]
In leap for quantum computing, silicon quantum bits establish a long-distance relationship
EurekAlert December 25, 2019 Silicon spin qubits have several advantages over superconducting qubits – they retain their quantum state longer than competing qubit technologies and they could be manufactured at low cost. A team of researchers in the US (Princeton University, industry) connected the qubits via a “wire” which is a narrow cavity containing a photon that picks up the message from one qubit and transmits it to the next qubit. The two qubits were located about half a centimeter apart. The team succeeded in tuning both qubits independently of each other while still coupling them to the photon. An […]
Lasers learn to accurately spot space junk
Phys.org December 24, 2019 Scientists have developed space junk identification systems, but it has proven tricky to pinpoint the swift, small specks of space litter. Researchers in China trained a back propagation neural network to recognize space debris using two correcting algorithms. The Genetic Algorithm and Levenberg-Marquardt optimized the neural network’s thresholds for recognition of space debris, ensuring the network wasn’t too sensitive and could be trained on localized areas of space. The team demonstrated the improved accuracy by testing against three traditional methods. The observation data of 95 stars was used to solve the algorithm coefficients from each method, […]
Paving the way for spintronic RAMs: A deeper look into a powerful spin phenomenon
Science Daily December 26, 2019 Extensive studies on Unidirectional spin Hall magnetoresistance (USMR) in metallic bilayers has found that its magnitude (∼10−5) is too small for practical applications. An international team of researchers(Japan,Vietnam) has demonstrated a giant USMR effect in a heterostructure of BiSb topological insulator – GaMnAs ferromagnetic semiconductors. They obtained a large USMR ratio of 1.1% and found that this giant USMR is governed not by the giant magnetoresistance like spin-dependent scattering but by magnon emission/absorption and strong spin-disorder scattering in the GaMnAs layer. Their results present a novel strategy to exploit spin-related phenomena in topological materials, which […]
Scientists create thin films with tantalizing electronic properties
Science Daily December 23, 2019 An international team of researchers (USA – SUNY New York, Los Alamos National Laboratory, Rensselaer Polytechnic Institute, China) has fabricated barium zirconium sulfide (BaZrS3) thin films by sulfurization of oxide films deposited by pulsed laser deposition. They showed that these films are n-type with carrier densities in the range of 1019-1020 cm−3. Temperature dependent conductivity measurements suggest shallow donor levels. By assuring that BaZrS3 is a promising candidate, these results potentially unleash a family of chalcogenide perovskites for optoelectronics such as photodetectors, photovoltaics, and light emitting diodes…read more. TECHNICAL ARTICLE
Scientists discover first antiferromagnetic topological quantum material
Science Daily December 19, 2019 An international team of researchers led by Spain has developed a crystal growing technique for intrinsically magnetic topological material manganese-bismuth telluride (MnBi2Te4) and characterized the physical properties of the crystals. The team was able to prove both in theory and in spectroscopic experiments that MnBi2Te4 is the first antiferromagnetic topological insulator (AFMTI) below its Néel temperature. They optimized the synthesis protocol for the new material so that MnBi2Te4 single crystals can be produced more easily. Recent findings show that there are even more structural derivatives of MnBi2Te4, which are relevant in the context of MTI…read […]
Space-time metasurface makes light reflect only in one direction
Phys.org December 20, 2019 Currently isolators and circulators based on the magneto-optic effect make the devices bulky and difficult for integration. Leveraging both spatial and temporal phase manipulation offered by an ultrathin nonlinear metasurface researchers at Pennsylvania State University experimentally demonstrated nonreciprocal light reflection at wavelengths around 860 nm. The metasurface creates spatial phase gradient and multi-terahertz temporal phase wobbling, which leads to unidirectional photonic transitions in both the momentum and energy spaces. They observed completely asymmetric reflections in forward and backward light propagations over a large bandwidth around 5.77 THz within a sub-wavelength interaction length of 150 nm. Their approach highlights a […]
Tweaks behind the rebirth of nearly discarded organic solar technologies
Science Daily December 19, 2019 Unlike silicon solar technology, non-fullerene acceptors (NFAs) can be shaped, made semi-transparent or colored and fine-tuned to free up and move electrons to generate electricity. Researchers at Georgia Institute of Technology have modeled tiny tweaks to molecular shapes and calculated corresponding energy conversion in a common NFA electron donor/acceptor pairing. Improved performance came from tweaks to a tiny component, a methoxy group, on the acceptor, and two positions out of four possible positions it took boosted the conversion of light into electricity from 6% to 12%…read more. Open Access TECHNICAL ARTICLE
Using a material’s ‘memory’ to encode unique physical properties
Science Daily December 20, 2019 A team of researchers in the US (University of Chicago, University of Pennsylvania) has shown that aging encodes a memory of the stresses imposed during preparation. Because of inhomogeneous local stresses, the material itself decides how to evolve by modifying stressed regions differently from those under less stress. Because material evolution occurs in response to stresses, aging can be “directed” to produce sought-after responses and unusual functionalities that do not inherently exist. Aging obeys a natural “greedy algorithm” as, at each instant, the material simply follows the path of most rapid and accessible relaxation. Their […]