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 […]
Category Archives: Materials science
A novel insulating state emerges in a 2D material
Nanowerk April 23, 2022 Within the Transition-metal dichalcogenides (TMD) family, iridium ditelluride (IrTe2) is ideally suited for the systematic study of competing factors that can affect a material’s electronic properties. An international team of researchers (USA – Lawrence Berkely National Laboratory, SLAC National Accelerator Laboratory, UC Berkeley, Sandford University, South Korea, Egypt) synthesized bilayer and monolayer IrTe2 samples and characterized their atomic and electronic structures. The analysis of the material showed that monolayer IrTe2 develops a large band gap that’s an order of magnitude larger than is typical for TMD systems, transforming the material into an insulator through the removal […]
New study solves mystery of how soft liquid droplets erode hard surfaces
Science Daily March 31, 2022 An international team of researchers (USA – University of Minnesota, Chile) has developed a method of high-speed stress microscopy, which measures the key dynamic properties of drop impact responsible for erosion, i.e., the shear stress and pressure distributions of impacting drops, with unprecedented spatiotemporal resolutions. Their experiments revealed the fast propagation of self-similar noncentral stress maxima underneath impacting drops and quantify the shear force on impacted substrates. They examined the deformation of elastic substrates under impact and uncovered impact-induced surface shock waves. The study opens the door for quantitative measurements of the impact stress of […]
Quantum ‘shock absorbers’ allow perovskite to exhibit superfluorescence at room temperature
Phys.org March 31, 2022 While analyzing the structure and optical properties of a common lead-halide hybrid perovskite an international team of researchers (USA – North Caroline State University, France) noticed the formation of polarons in these materials. Their analysis showed that formation of large polarons creates a thermal vibrational noise filter mechanism that they called ‘Quantum Analog of Vibration Isolation,’ or QAVI, which is like a shock absorber protecting the dipoles. When they are protected by the shock absorbers, the dipoles can synchronize and exhibit superfluorescence. According to the researchers, QAVI is an intrinsic property that exists in certain materials, […]
Scientists develop environmentally safe, frost-resistant coatings
Phys.org April 1, 2022 Researchers at the University of Illinois have proposed a design rationale for developing a family of cryoprotectant and phase change material-based compositions in the form of mixtures, non-aqueous emulsions-creams and gels. An in situ generated surface hydration layer protects the underlying substrate from a variety of foulants, varying from ice to disease-causing bacteria. Each formulation utilizes unique chemistry to curtail the embodied cryoprotectant loss and can be easily applied as an all-in-one sprayable/paintable coating capable of significantly outperforming untreated industrial materials in terms of their ability to delay condensation-frosting and shed ice simultaneously. They observed an […]
Decoding a material’s ‘memory’
Science Daily March 24, 2022 While it has been known that individual particle distribution influences yield point, or flow, in disordered materials, it has been challenging to study this phenomenon since the field lacks ways to “quantify” disorder in such materials. Researchers at the University of Pennsylvania tracked individual particles on top of a liquid-air interface. Then, they used a magnetic needle that moves back and forth to apply a shearing force. With this system, the researchers can systematically apply forces to 50,000 particles, track their detailed movement, and use complex image analysis to see if two neighboring particles remain […]
Team achieves 30-fold enhancement of thermoelectric performance in polycrystalline tin selenide
Phys.org March 28, 2022 Tin selenide (SnSe) is known to exhibit a record high energy conversion (ZT) in its single crystal form. However, the performance deteriorates in practical polycrystals because of a low electronic conductivity (σ) and a high thermal conductivity (κ). Researchers in Japan enhanced the ZT of polycrystalline SnSe by demonstrating a high σ and a low κ simultaneously by introducing tellurium (Te) ion into the structure of SnSe. The large-size Te ion in Sn(Se1−xTex) forms weak Sn-Te bonds, leading to the high-density formation of hole-donating Sn vacancies and the reduced phonon frequency and enhanced phonon scattering. This […]
Water as a ‘glue’ for elasticity enhanced, wet attachment of biomimetic structures
Phys.org March 29, 2022 Octopus, clingfish, and larva use soft cups to attach to surfaces under water. Using a novel micro cup, fabricated by two-photon lithography, coupled with in situ pressure sensor and observation cameras, an international team of researchers (Germany, USA – University of Illinois) has detailed the nature of its attachment/detachment under water. It involves elasticity-enhanced hydrodynamics generating “self-sealing” and high suction at the cup-substrate interface, converting water into “glue.” Detachment is mediated by seal breaking. They identified three distinct mechanisms of breaking including elastic buckling of the cup rim. A mathematical model described the interplay between the […]
When a band falls flat: Searching for flatness in materials
Science Daily March 30, 2022 An international team of researchers (USA – Princeton University, France, Germany, China, Spain) has developed a catalog of the naturally occurring three-dimensional stoichiometric materials with flat bands around the Fermi level. They considered 55,206 materials from the Inorganic Crystal Structure Database which provides their structural parameters, space group, band structure, density of states and topological characterization and combined several direct signatures and properties of band flatness with a high-throughput analysis of all crystal structures. From this set they created the Materials Flatband Database website https://www.topologicalquantumchemistry.fr/flatbands/ , with its own search engine for future theoretical and […]
A sieve for molecules
Science Daily March 7, 2022 Scientists have long tried to use graphene as a sieve. However, it doesn’t have any pores. An international team of researchers (Germany, USA – Yale University) found that bilayer silica composed of corner-sharing (SiO4) units to be permeable for small molecules due to its intrinsic lattice openings. Their study sheds light on the mass transport properties of freestanding 2D SiO2 upon using atomic layer deposition (ALD) to grow large-area films on Au/mica substrates followed by transfer onto Si3N4 windows. Permeation experiments with gaseous and vaporous substances revealed the suspended material to be porous, but the […]