Phys.org March 22, 2024 Nanomaterials exhibit excitonic quantum processes occurring at room temperature. However, low dimensionality imposes strict requirements for conventional optical excitation. Researchers in Japan found that exciton transfer in carbon-nanotube/tungsten-diselenide heterostructures occur when alignment could be systematically varied. The mixed-dimensional heterostructures displayed a pronounced exciton reservoir effect where the longer-lifetime excitons within the two-dimensional semiconductor were funneled into carbon nanotubes through diffusion. The new excitation pathway presented several advantages, including larger absorption areas, broadband spectral response, and polarization-independent efficiency. When band alignment was resonant, they observed substantially more efficient excitation via tungsten diselenide compared to direct excitation of […]
Tag Archives: S&T Japan
Photon-like electrons in a four-dimensional world discovered in a real material
Phys.org March 14, 2024 Because of their differences from standard electrons, Dirac electrons are expected to add unprecedented electronic properties to materials. Researchers in Japan discovered a method enabling selective observation of the Dirac electrons in materials. Using electron spin resonance, to directly observe unpaired electrons in materials to distinguish differences in character, they established a method to determine their scope of action in the materials and their energies. They showed that electron spin resonance revealed that α-ET2I3 (ET = bis(ethylenedithio)-tetrathiafulvalene) at 1 bar contained a nearly three-dimensional DFs above ∼100 K coexisting with standard fermions. The close charge-transfer ET–I3 […]
Projection mapping leaves the darkness behind
Phys.org March 18, 2024 Projection mapping (PM) typically requires a dark environment to achieve high-quality projections, limiting its practicality. Researchers in Japan overcame this limitation by replacing conventional room lighting with heterogeneous projectors. These projectors replicated environmental lighting by selectively illuminating the scene, excluding the projection target. They developed distributed projector optimization framework designed to effectively replicate environmental lighting and incorporated a large-aperture projector, in addition to standard projectors, to reduce high-luminance emitted rays and hard shadows. To validate their approach, they conducted a series of quantitative and qualitative experiments. They successfully demonstrated that their projector-based lighting system significantly enhanced […]
New type of tunable filter reveals the potential for terahertz wireless communications
Phys.org March 11, 2024 Researchers in Japan constructed a tunable Fabry–Perot interferometer (FPI) by controlling the effective refractive index of pitch-variable subwavelength gratings (PV-SWGs) that were incorporated into an FP cavity. The period of the PV-SWG could be varied to change the effective refractive index and shift the optical resonant frequency of the FPI. Compared with conventional methods that tune the optical resonance by adding fillers or deforming the cavity, the FPI obtained a higher transmission and quality factor (Q-factor) for the transmittance peak, and its resonant frequency could be shifted by simply stretching the PV-SWG. According to the researchers […]
Paper AI sensor mimics brain for health monitoring
Nanowerk March 11, 2024 Physical reservoir computing (PRC), which mimics the human brain using physical phenomena, offers a low-power consumption architecture. However, creating a flexible and easily disposable sensors using PRC capable of processing optical signals with sub-second response times suitable for biological signals presents a challenge. Researchers in Japan designed disposable and flexible paper-based optoelectronic synaptic devices which are composed of nanocellulose and ZnO nanoparticles, for PRC. The device exhibited synaptic photocurrent in response to optical input. The memory capacity of short-term memory task, indicating the device’s ability to store past information was 1.8. It could recognize handwritten digits […]
Light stimulates a new twist for synthetic chemistry
Nanowerk February 28, 2024 Photoinduced concerted multiple-bond rotation has been proposed in some biological systems. However, the observation of such phenomena in synthetic systems has been a challenge in the photochemistry field. Researchers in Japan described a chalcogen-substituted benzamide system that exhibits photoinduced dual bond rotation in heteroatom-containing bonds. Introduction of the chalcogen substituent into a sterically hindered benzamide system provided sufficient kinetic stability and photosensitivity to enable the photoinduced concerted rotation. The presence of two different substituents on the phenyl ring in the thioamide derivative enabled the generation of a pair of enantiomers and E/Z isomers. Using these four […]
Coordination polymer crystals show promise as new generation of light sources for industry, medicine
Phys.org February 20, 2024 Luminescent lanthanide coordination polymer crystals (LCPCs) provide a high level of structural tunability, including size- and morphology-dependent properties; therefore, they are promising materials for next-generation phosphors in a wide range of applications such as light emitting diodes. By controlling the morphology of thermostable europium coordination polymer crystals researchers in Japan developed a novel red phosphor with narrow linewidth emission and characterized them through analysis. Size tunable crystalline polymer spheres had high internal quantum efficiency and high thermostability, and exhibited dispersibility in PMMA Poly(methyl methacrylate) media… read more. Open Access TECHNICAL ARTICLE
Researchers solve a foundational problem in transmitting quantum information
Phys.org February 13, 2024 To investigate light-matter hybrid excitations in a quantum dot (QD) THz resonator coupled system researchers in Japan fabricated a gate-defined QD near a THz split-ring resonator (SRR) by using a AlGaAs/GaAs two-dimensional electron system. By illuminating the system with THz radiation, the QD showed a current change whose spectrum exhibited coherent coupling between the electrons in the QD and the SRR as well as coupling between the two-dimensional electron system and the SRR. The latter coupling entered the ultrastrong coupling regime and the electron excitation in the QD also exhibited coherent coupling with the SRR with […]
Communing with nothingness
Nanowerk November 6, 2023 Light–matter interaction in the ultrastrong coupling regime is attracting considerable attention owing to its applications to coherent control of material properties by a vacuum fluctuation field. However, electrical access to such an ultra-strongly coupled system is very challenging. Researchers in Japan have fabricated a gate-defined quantum point contact (QPC) near the gap of a terahertz (THz) split-ring resonator (SRR) fabricated on a GaAs two-dimensional (2D) electron system. By illuminating the system with external THz radiation, the QPC showed a photocurrent spectrum which exhibited significant anticrossing that came from coupling between the cyclotron resonance of the 2D […]
Optical-fiber based single-photon light source at room temperature for next-generation quantum processing
Science Daily November 2, 2023 Rare-earth (RE) atoms in solid-state materials are attractive components for photonic quantum information systems because of their coherence properties even in high-temperature environments. Researchers in Japan performed the single-site optical spectroscopy and optical addressing of a single RE atom in an amorphous silica optical fiber at room temperature. The single-site optical spectroscopy of the tapered RE-doped fiber showed nonresonant emission lines similar to those seen in the case of an unstructured fiber and the autocorrelation function of photons emitted from the fiber showed the antibunching effect due to the spatial isolation given by the tapered […]