Phys.org March 21, 2023 In strong correlations and superconductivity in twisted-bilayer graphene the superposition of two twisted honeycomb lattices generating a moiré pattern is the key to the observed flat electronic bands, slow electron velocity and large density of states. An international team of researchers (USA – University of Chicago, China) demonstrated quantum simulation of superfluid to Mott insulator transition in twisted-bilayer square lattices based on atomic Bose–Einstein condensates loaded into spin-dependent optical lattices. The lattices are made of two sets of laser beams that independently address atoms in different spin states, which form the synthetic dimension accommodating the two […]
Shaping with light – a novel method for crafting chiral nanostructures with lasers
Nanowerk March 22, 2023 Chiral nanostructures based on semiconductors exhibit pronounced properties of chiral luminescence and optoelectronic responses, which are fundamental for chiroptoelectronic devices. Researchers in China showed polarization-directed oriented growth of platinum oxide/sulfide nanoparticles based on optical dipole interactions and near-field–enhanced photochemical deposition. By rotating the polarization during the irradiation or employing vector beam, both three dimensional and planar chiral nanostructures could be obtained, which is extendable to cadmium sulfide. The chiral superstructures exhibited broadband optical activity with a g-factor of ~0.2 and a luminescence g-factor of ~0.5 in the visible, making them promising candidate for chiroptoelectronic devices… read […]
Stalactites and stalagmites in the battery?
Science Daily March 17, 2023 The role of grain boundaries in the nucleation and dendritic growth of metallic lithium is not yet fully understood. Researchers in Germany used operando Kelvin probe force microscopy measurements to map locally time-dependent electric potential changes in the Li6.25Al0.25La3Zr2O12 garnet-type solid electrolyte. They found that the Galvani potential dropped at grain boundaries near the lithium metal electrode during plating as a response to the preferential accumulation of electrons. Time-resolved electrostatic force microscopy measurements and quantitative analyses of lithium metal formed at the grain boundaries under electron beam irradiation supported this finding. Based on these results, […]
Surprise in the quantum world: Disorder leads to ferromagnetic topological insulator
Nanowerk March 21, 2023 The recent realizations of the quantum anomalous Hall effect in MnBi2Te4 and MnBi4Te7 benchmark the (MnBi2Te4)(Bi2Te3)n family as a promising hotbed for further quantum anomalous Hall effect improvements. However, the quantum anomalous Hall effect realization is complicated in MnBi2Te4 and MnBi4Te7 due to the substantial antiferromagnetic coupling between the septuple layers. Although ferromagnetic state can be stabilized by interlacing the septuple layers with an increasing number n of Bi2Te3 quintuple layers the mechanisms driving the FM state and the number of necessary quintuple layers are not understood, and the surface magnetism remains obscure. An international team […]
Team develops silicon photonic MEMS compatible with semiconductor manufacturing
Phys.org March 22, 2023 Silicon’s relatively weak electro-optic effects result in modulators with a significant footprint and thermo-optic tuning devices that require high power consumption, which are substantial impediments for very large-scale integration in silicon photonics. An international team of researchers (Switzerland, Sweden, Belgium, Ireland) has introduced a silicon photonic MEMS platform consisting of high-performance nano-opto-electromechanical devices fully integrated alongside standard silicon photonics foundry components, with wafer-level sealing for long-term reliability, flip-chip bonding to redistribution interposers, and fibre-array attachment for high port count optical and electrical interfacing. Their experimental demonstration of fundamental silicon photonic MEMS circuit elements, including power couplers, […]
Ultra-lightweight multifunctional space skin created to withstand extreme conditions in space
Nanowerk March 22, 2023 Current tissue engineering approaches combine different scaffold materials with living cells to provide biological substitutes that can repair and eventually improve tissue functions. Both natural and synthetic materials have been fabricated for transplantation of stem cells and their specific differentiation into muscles, bones, and cartilages. One of the key objectives for bone regeneration therapy to be successful is to direct stem cells’ proliferation and to accelerate their differentiation in a controlled manner using growth factors and osteogenic inducers. An international team of researchers (Singapore, South Korea) has shown that graphene provides a promising biocompatible scaffold that […]
Top 10 Science and Technology Inventions for the Week of March 17, 2023
01. Breakthrough discovery in materials science challenges current understanding of photoemission 02. Closing in on next-generation atom-thick photonic devices 03. Experiment unlocks bizarre properties of strange metals 04. Magnetism fosters unusual electronic order in quantum material 05. Novel tunable 2D nanosheets enable many semiconductor applications, ranging from electronics to photocatalysis 06. Shape memory achieved for nano-sized objects 07. Researchers develop soft robot that shifts from land to sea with ease 08. Researchers develop ultraefficient white light laser on a chip 09. Resilient bug-sized robots keep flying even after wing damage 10. Scientists demonstrate time reflection of electromagnetic waves And others […]
Breakthrough discovery in materials science challenges current understanding of photoemission
Phys.org March 14, 2023 Currently existing photocathodes are based on conventional metals and semiconductors that were discovered six decades ago with sound theoretical underpinnings. An international team of researchers (China, Japan, USA- Northeastern University) has observed unusual photoemission properties of a reconstructed surface of SrTiO3(100) single crystals. Unlike other positive-electron-affinity (PEA) photocathodes, their PEA SrTiO3 surface produced discrete secondary photoemission spectra at room temperature, characteristic of the efficient negative-electron-affinity photocathode materials. Using several photon energies they were able to produce a very intense coherent secondary photoemission. According to the researchers the observed emergence of coherence in secondary photoemission points to […]
Building an understanding of quantum turbulence from the ground up
Phys.org March 15, 2023 In macroscopic quantum condensates the quasiclassical turbulent dynamics at large scales is altered at small scales, where the quantization of vorticity is essential. The nature of this transition remains an unanswered question. An international team of researchers (Finland, UK, Israel) expanded the concept of wave-driven turbulence to rotating quantum fluids where the spectrum of waves extends to microscopic scales as Kelvin waves on quantized vortices. They excited inertial waves at the largest scale by periodic modulation of the angular velocity and observed dissipation-independent transfer of energy to smaller scales and the eventual onset of the elusive […]
Closing in on next-generation atom-thick photonic devices
Phys.org March 13, 2023 The materials used to make photodetectors often hamper efforts to make improved broadband nanoscale photodetectors. To overcome these difficuties a team of researchers in the US (San Francisco State University, Stanford University) developed a photodetector that has improved sensitivity in the ultraviolet to near-infrared light range. High photoresponsivity at wavelength 400 nm measured at 77 K, which translates into an external quantum efficiency. The 90% rise time of the devices at 77 K is 0.1 ms, suggesting they can operate at the speed of ≈10 kHz. High-performance broadband photodetector with spectral coverage ranging from 380 to 1000 nm was demonstrated. According to […]