Nanowerk October 27, 2022 With the discovery of nodal-line semimetals, the notion of the Dirac point has been extended to lines and loops in momentum space. However, experimental evidence for the enhanced correlations in nodal-line semimetals is sparse. An international team of researchers (USA -Columbia University, University of Arkansas, Pennsylvania State University, Florida State University, National High Magnetic Field Laboratory, Flatiron Institute, China, the Netherlands, Germany) found prominent correlation effects in a nodal-line semimetal compound, ZrSiSe, through experiments and density functional theory calculations. They observed two fundamental spectroscopic hallmarks of electronic correlations: strong reduction of the free-carrier Drude weight and […]
Category Archives: Materials science
Functional carbon materials for addressing dendrite problems in metal batteries
Phys.org October 25, 2022 Metal batteries that directly use active metals as anodes are promising solutions for energy upgrade of battery technologies, but they suffer from dendrite problems. Researchers in China have demonstrated that functional carbon materials (FCMs) can suppress metal dendrites. They reviewed recent progress in using FCMs to deal with dendrite problems. The review focused on the surface chemistry and multi-dimensional carbon material engineering, which systematically overcomes the problems through diverse methods, such as reinforcing desolvation, improving interface compatibility, homogenizing electric field, buffering volume expansion and lattice mismatch. They refined the long-standing debate about whether surface defects in […]
A new process to build 2D materials made possible by quantum calculations
Phys.org October 10, 2022 Ultra-thin 2D materials are frequently grown by exposing a hot metal surface to a specific gas, which results in the gas decomposing on the metal and forming the desired 2D material. Due to the hot temperatures involved, it is difficult to monitor the growth of 2D materials during the several intermediate steps involved before the 2D material is completed. An international team of researchers (Austria, UK) utilized helium atom scattering to discover and control the growth of novel 2D h-BN nanoporous phases during the CVD process. They found that prior to the formation of h-BN from […]
Exotic electronic effect found in 2D topological material
Phys.org September 26, 2022 When external or intrinsic parameters break symmetries, global properties of topological materials change drastically. While a rich variety of non-trivial quantum phases could in principle also originate from broken time-reversal symmetry, realizing systems that combine magnetism with complex topological properties is remarkably elusive. An international team of researchers (Germany, USA – UC Davis) demonstrated that giant open Fermi arcs are created at the surface of ultrathin hybrid magnets where the Fermi-surface topology is substantially modified by hybridization with a heavy-metal substrate. The interplay between magnetism and topology allows for control of shape and the location of […]
Researchers create synthetic rocks to better understand how increasingly sought-after rare earth elements form
Phys.org September 30, 2022 Researchers in Ireland studied the interaction between rare earth element (REE)-rich (La, Pr, Nd, Dy) aqueous solutions, dolomite (CaMg(CO3)2), and aragonite (CaCO3) at low temperature hydrothermal conditions (25–220 °C) to understand the formation of REEs. They found that the newly formed REE-bearing carbonates in La-, Pr-, and Nd-doped systems follow the crystallization sequence: lanthanite [REE2(CO3)3·8H2O] → kozoite [orthorhombic REECO3(OH)] → hydroxylbastnasite [hexagonal REECO3(OH)]. The interaction of Dy-bearing solutions with dolomite results only in the crystallization of kozoite [orthorhombic DyCO3(OH)]. However, experiments with aragonite reveal a two-step crystallization pathway: tengerite [Dy2(CO3)3·2-3(H2O)] → kozoite [orthorhombic DyCO3(OH)]. The temperature, […]
Terahertz light from superconducting stripes
Phys.og September 22, 2022 The interplay between charge order and superconductivity remains one of the central themes of research in quantum materials. In the case of cuprates, the coupling between striped charge fluctuations and local electromagnetic fields is especially important, as it affects transport properties, coherence, and dimensionality of superconducting correlations. An international team of researchers (Germany, USA – Harvard University, Brookhaven National Laboratory, Switzerland, UK) studied the emission of coherent terahertz radiation in single-layer cuprates of the La2-xBaxCuO4 family, for which this effect is expected to be forbidden by symmetry. They found that emission vanishes for compounds in which […]
Researchers report counterintuitive friction effect
Phys.org September 6, 2022 While the impact of mechanical energy and heat on the friction and wear behavior of dry metallic interfaces has been the focus of extensive research in the past, the effect of extreme speeds on the near-surface deformation mechanisms in polycrystalline metals has remained poorly understood. An international team of researchers (Austria, UK) explored sliding velocities ranging from 10 to 2560 m/s via large-scale molecular dynamics simulations to identify three distinct deformation regimes in CuNi alloys. The microstructural response did not vary much for any of the considered systems up to sliding velocities of 40 m/s, but […]
Neural networks predict forces in jammed granular solids
Phys.org September 1, 2022 Force chains are quasi-linear self-organised structures carrying large stresses and are ubiquitous in jammed amorphous materials like granular materials, foams or even cell assemblies. Understanding force chains is crucial in describing the mechanical and transport properties of granular solids and this applies in a wide range of circumstances—for example how sound propagates or how sand responds to mechanical deformation. Predicting where they will form upon deformation is crucial to describe the properties of such materials but remains an open question. An international team of researchers (Germany, Belgium, UK) demonstrated that graph neural networks (GNN) can accurately […]
Small molecules, giant (surface) potential
Phys.org August 26, 2022 The performance of organic optoelectronic and energy-harvesting devices is largely determined by the molecular orientation and resultant permanent dipole moment, yet this property is difficult to control during film preparation. Researchers in Japan have demonstrated the active control of dipole direction in organic glassy films by physical vapour deposition. It was obtained by utilizing the small surface free energy of a trifluoromethyl unit and intramolecular permanent dipole moment induced by functional groups. According to the researchers their work could pave a way toward the formation of spontaneously polarized organic glassy films, leading to improvement in the […]
Damage-reporting and self-healing skin-like polymeric coatings
Nanowerk August 24, 2022 As it is difficult to determine whether the currently used polymeric coatings applied to the surfaces of automobiles, ships, etc. to protect them from the external environment are already damaged or not, these non-reusable coatings must be regularly replaced, leading to a large amount of waste generation and high disposal costs. Researchers in South Korea have demonstrated mechanochromic and thermally reprocessable thermosets that can be used for autonomic damage reporting and self-healing coatings. A mechanochromic molecule, spiropyran (SP), was covalently incorporated into thermoreversible Diels–Alder (DA) cross-linking networks. Mechanical activation of SPs in DA networks was confirmed […]