Science Daily April 9. 2024 Moiré systems made from stacked two-dimensional materials host correlated and topological states that can be electrically controlled with applied gate voltages. One prevalent form of topological state that can occur are Chern insulators that display a quantum anomalous Hall effect. An international team of researchers (USA – UC Berkeley, Lawrence Berkeley National Laboratory, Japan) manipulated Chern domains in an interaction-driven quantum anomalous Hall insulator made from twisted monolayer–bilayer graphene and observed chiral interface states at the boundary between different domains. By tuning the carrier concentration, they stabilized neighbouring domains of opposite Chern number that then […]
Old crystal, new story for enhancing deep ultraviolet laser performance
Phys.org April 1, 2024 Researchers in China obtained 60-mW solid-state deep ultraviolet (DUV) laser at 193 nm with narrow linewidth with two stages of sum frequency generation in lithium triborate (LBO) crystals. The pump lasers were derived from a homemade Yb-hybrid laser. The Yb-hybrid laser was power scaling by a 2mm×2mm×30mm Yb:YAG bulk crystal. The 220-mW DUV laser at 221 nm, and the 193-nm laser delivered an average power of 60 mW with a pulse duration of 4.6 ns. The conversion efficiency reached 27% for 221 to 193 nm and 3% for 258 to 193 nm. According to the researchers […]
Physicists discover a novel quantum state in an elemental solid
Phys.org April 10, 2024 The nexus of topology and interactions yield important research directions. Using tunnelling microscopy, photoemission spectroscopy and a theoretical analysis an international team of researchers (USA – Princeton University, University of Alabama at Birmingham, Florida State University, Oak Ridge National laboratory, UK, Singapore, China, Switzerland) has shown a “hybrid” topological phase of matter in elemental-solid arsenic. They showed that arsenic features a conjoined strong and higher-order topology that stabilizes a hybrid topological phase. Measurements unraveled a unique geometry of topologically induced step-edge conduction channels. Using theoretical models, they showed that the existence of gapless step-edge states in […]
Propagating dimensions of light: Deforming versatile non-diffractive beams along the optical trajectory
Phys.org April 8, 2024 Despite the numerous types of non-diffraction beam generation technologies, the 3D deformation and intricate wavefront shaping of structures during propagation have yet to be studied through the lens of nanophotonic devices. An international team of researchers (Singapore, Spain) demonstrated the dynamic conversion of a circular Airy beam (CAB) to a Bessel beam with a single-layer spin-selective metasurface. The spatial transformation developed from the interplay of 1D local and 2D global phases, facilitating the 3D control of non-diffractive light fields. Overall phase gradient and orbital angular momentum altered the propagation direction and transverse fields of complex amplitude […]
Quantum crystal of frozen electrons – the Wigner crystal – is visualized for the first time
Nanowerk April 10, 2024 A variety of two-dimensional systems have shown evidence for Wigner crystals (WCs), electrons crystallized into a closely packed lattice. However, a spontaneously formed classical or quantum WC has never been directly visualized. An international team of researchers (USA – Princeton University, UC Berkeley, Lawrence Berkeley National Laboratory, Japan) imaged a magnetic-field-induced electron WC in Bernal-stacked bilayer graphene and examined its structural properties as a function of electron density, magnetic field, and temperature. At high fields and the lowest temperature, they observed a triangular lattice electron WC in the lowest Landau level. The WC possessed the expected […]
The spontaneous emergence of 1D superconducting stripes at a 2D interface in an oxide heterostructure
Phys.org April 8, 2024 Magnetism can cause a modulation of superconducting pairing in real space in both copper-based and iron-based materials. Researchers in China reported on the discovery of a spatially varying superconducting state residing at the interface between KTaO3 and ferromagnetic EuO. Electrical transport measurements revealed different values of the critical temperature and magnetic field at which the superconductivity breaks down when current was applied along the two orthogonal in-plane directions. This anisotropy occurred in low-carrier-density samples that were characterized by strong coupling between the Ta 5d and Eu 4f electrons, whereas in high-carrier-density samples, the coupling was weakened, […]
Unlocking exotic physics: Exploring graphene’s topological bands in super-moiré structures
Phys.org April 4, 2024 Moiré-pattern-based potential engineering has become an important way to explore exotic physics in a variety of two-dimensional condensed matter systems. An international team of researchers (Spain, Singapore) demonstrated theoretically that a single layer of graphene, when placed between two bulk boron nitride crystal substrates with the appropriate twist angles, could support a robust topological ultra flat band emerging as the second hole band. According to the researchers this is one of the simplest platforms to design and exploit topological flat bands… read more. TECHNICAL ARTICLE
Waterproof ‘e-glove’ could help scuba divers communicate
Nanowerk April 10, 2024 Existing tactile sensing gloves fall short in terms of user comfort and are ill-suited for underwater applications. Researchers in China proposed and constructed a flexible hand gesture recognition glove (GRG) that contained high-performance micropillar tactile sensors (MPTSs) inspired by the flexible tube foot of a starfish. The sensor has a wide working range, superfast response time, reliable repeatability, and a low limit of detection and they were waterproof. When integrated with machine learning algorithm, the GRG system achieved intelligent recognition of 16 hand gestures under water, extending real-time and effective communication capabilities for divers. According to […]
Top 10 Science and Technology Inventions for the Week of April 05, 2024
01. 100 kilometers of quantum-encrypted transfer 02. Intelligent liquid 03. Magnetic avalanche triggered by quantum effects: ‘Barkhausen noise’ detected for first time 04. New hydrogel can stretch to 15 times its original size 05. Researchers discover dual topological phases in an intrinsic monolayer crystal 06. Room-temperature 2D magnet: Electronic-structure insights 07. ‘Shear sound waves’ provide the magic for linking ultrasound and magnetic waves 08. A solar cell you can bend and soak in water 09. Universal brain-computer interface lets people play games with just their thoughts 10. A simple way to harvest more ‘blue energy’ from waves And others Atmospheric […]
100 kilometers of quantum-encrypted transfer
Phys.org April 2, 2024 Continuous-variable (CV) quantum key distribution (QKD) with coherent states and coherent detection integrates well with existing telecommunication networks. Thus far, long-distance CV-QKD has only been demonstrated using a highly complex scheme where the local oscillator is transmitted, opening security loopholes for eavesdroppers, and limiting potential applications. Researchers in Denmark have demonstrated a long-distance CV-QKD experiment with a locally generated oscillator over a 100-kilometer fiber channel with a total loss of 15.4 decibels. This was done by controlling the phase noise–induced excess noise through a machine learning framework for carrier recovery and optimizing the modulation variance. They […]