物理最新文献

In this paper, we numerically investigate the design of an all-dielectric terahertz metasurface sensor with an ultra-high Q-factor, utilizing the concept of bound states in the continuum (BIC). The proposed metasurface consists of silicon-based cylindrical disks arranged as metamolecules. It is observed that two resonant modes are formed at 3.79 THz and 4.19 THz under symmetric conditions. By introducing a local asymmetry parameter (α) to break the structural symmetry, a leaky channel emerges, converting the ideal BIC into a quasi-BIC (q-BIC). This results in a sharp resonance at 4.06 THz with a Q-factor of 1.5 ×(:{10}^{4}). The numerically evaluated sensing performance demonstrates a high refractive index sensitivity of 1.0746 THz/RIU and a figure of merit (FOM) of 10854.56/RIU over a refractive index range of 1.00-1.15. Tuning the asymmetry further enhances the FOM up to 41330.77/RIU. The proposed metasurface finds strong potential for high-precision sensing, detection, and imaging in the terahertz frequency regime.

A metal-insulator-metal (MIM) parallel plate thin-film capacitor of ceramic dielectric was fabricated using an n-type silicon wafer substrate and characterized electrically. The ferroelectric perovskite BST36 (Ba_0.36, Sr_0.64)TiO₃ thin film dielectric was deposited via the RF magnetron sputtering technique, and the film is employed as a dielectric for the parallel plate ceramic capacitor. A molybdenum disilicide (MoSi₂) thin film has been deposited via the DC magnetron sputtering technique, and the sheet resistance was 5.611 Ωcm^− 2, after thermal processing. It has been used as a bottom metal contact for the device. While indium (In), copper (Cu), and silver (Ag) were deposited via the thermal evaporation technique and employed as top contact electrodes for the device. Molybdenum disilicide (MoSi₂) has been used again as a top contact electrode as well as a bottom electrode. The capacitor was electrically characterized at room temperature under a 10 VDC bias and 1 MHz frequency. Measurements of dielectric loss, dielectric constant, and capacitance density were depended on the device structure and electrode material. The results of the MIM parallel plate capacitor structure of Ag/BST/MoSi₂/n-Si exhibited the highest capacitance density achievement of 405 nFcm^− 2 with a dielectric loss of 0.048. An optimal recorded dielectric loss was 0.024 at 10 VDC for the device structure In/BST/MoSi₂/n-Si. The MoSi₂/BST/MoSi₂/n-Si a full parallel-plate ceramic capacitor device structure had a capacitance density of 47 nFcm^− 2, a dielectric constant of 22.3; and a dielectric loss of 0.035.

A novel plasmonic bandpass filter is proposed, comprising an infinity-shaped resonator integrated with metal-insulator-metal (MIM) waveguide structures. The proposed profile enables tunable spectral filtering in the near-infrared region. Owing to its unique structure, the resonator supports three distinct resonant modes, producing a characteristic triple-peak transmission spectrum spanning the wavelength range of (:0.8-3:mu:m). Numerical simulations confirm that the spectral response of the proposed waveguide-consisting resonance positions, bandwidth and transmission intensities-can be precisely matched by adjusting the resonator’s geometric parameters. This filter demonstrates a high transmission efficiency (more than 0.8) and a desirable quality factor at the subwavelength-scale, which indicates its originality and importance. The tunable narrowband performance in a wide spectral window highlights its potential for diverse applications in optical sensing, biomedical imaging, spectral filtering, optoelectronic systems as well as astronomical instrumentation.

This work demonstrates the simple, economical, and rapid synthesis of magnesia oxide (Mn₂O₃), copper oxide (CuO), and their compound Mn₂O₃/CuO composite, employing fundamental green practices. The as-synthesized Mn₂O₃, CuO, and Mn₂O₃/CuO have been evaluated using X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), and field-emission scanning electron microscopy (FESEM). The presence of distinct Mn₂O₃ and CuO phases, as well as the interphase between them, is evident in the TEM micrographs. Using the Tauc plot from absorption spectra, the energy bandgaps of pure Mn₂O₃, CuO, and the Mn₂O₃/CuO composite were estimated to be 2.6, 2.1, and 3.2 eV, respectively. The obtained materials were investigated for their photoluminescence (PL) and chromaticity characteristics to understand interfacial charge-transfer behavior. The PL spectra reveal broad blue - green emissions with main peaks located at 414 –437 nm for Mn₂O₃, 414 –439 nm for CuO, and a slightly red-shifted, intensified band at 435 nm for the Mn₂O₃/CuO composite. The corresponding CIE 1931 chromaticity coordinates (x ≈ 0.31, y ≈ 0.58) confirm a vivid green emission region, indicating improved color purity and radiative efficiency. These results demonstrate that coupling Mn₂O₃ with CuO tailors the electronic band alignment, suppresses non-radiative losses, and promotes strong visible luminescence, making the Mn₂O₃/CuO nanocomposite a promising candidate for green light - emitting and optoelectronic devices.

Reactions induced by alpha particles, which play an important role in nuclear astrophysics, were investigated at energies below the Coulomb barrier using our IFIN-HH facilities. These include the 3 MV Tandetron™ accelerator [1], a local laboratory and the ultra-low background laboratory (mu )Bq [2] located in a salt mine. Thick Zn metal targets were irradiated at laboratory energies in the range (hbox {E}_{alpha }) = 5.4–8.0 MeV in 0.20 or 0.25 MeV steps. By measuring the prompt gamma-ray yields and the decay of radioisotopes produced in each reaction, in the Nuclear Astrophysics Group (NAG) and the (mu )Bq laboratories [3], we determined the thick target yields, which were subsequently used to evaluate the reaction cross sections. We succeeded in determining the cross section for (alpha )+⁶⁴Zn for the proton evaporation and radiative alpha capture channels at the lowest energies ever measured, deep inside the Gamow window for stellar processes at temperatures of 2–3 GK.

Systematic comparisons across theoretical predictions for the properties of dense matter, nuclear physics data, and astrophysical observations (also called meta-analyses) are performed. Existing predictions for symmetric nuclear and neutron matter properties are considered, and they are shown in this paper as an illustration of the present knowledge. Asymmetric matter is constructed assuming the isospin asymmetry quadratic approximation. It is employed to predict the pressure at twice saturation energy-density based only on nuclear-physics constraints, and we find it compatible with the one from the gravitational-wave community. To make our meta-analysis transparent, updated in the future, and to publicly share our results, the Python toolkit nucleardatapy is described and released here. Hence, this paper accompanies nucleardatapy, which simplifies access to nuclear-physics data, including theoretical calculations, experimental measurements, and astrophysical observations. This Python toolkit is designed to easily provide data for: (i) predictions for uniform matter (from microscopic or phenomenological approaches); (ii) correlation among nuclear properties induced by experimental and theoretical constraints; (iii) measurements for finite nuclei (nuclear chart, charge radii, neutron skins or nuclear incompressibilities, etc.) and hypernuclei (single particle energies); and (iv) astrophysical observations. This toolkit provides data in a unified format for easy comparison and provides new meta-analysis tools. It will be continuously developed, and we expect contributions from the community in our endeavor.

We analyze the tree-level generation of entanglement through some key scattering processes in massless quantum electrodynamics on canonical noncomutative spacetime with space-space type of noncommutativity. The fermions in the noncommutative theory will be zero charge fermions. The scattering processes we shall study do not occur in ordinary Minkowski spacetime. We shall use the concurrence to characterize the amount of entanglement generated through a given scattering process. We shall show that, at tree-level, the concurrence for the scattering of two photons of opposite helicity is given by the same expression as in the case of the scattering of gluons in ordinary Minkowski spacetime. Thus, maximal entanglement is achieved if and only if the polar scattering angle is equal to (pi /2). We also compute the concurrence for the head-on collision in the laboratory reference frame of two fermions of opposite helicity to obtain the same result as in the case of photon scattering. Finally, we shall study a type of collision at right angles in the laboratory frame of fermions with opposite helicity. We show that in the latter case the concurrence depends on energy of the incoming fermions, the noncommutativity matrix (theta ^{ij}), the polar, (theta ), and azimuth angle, (phi ), of the zero-momentum frame of the incoming fermions. In this latter case we see that when (theta =pi /2) there are values of (phi ) for which no entanglement is generated.