Applied Physics A最新文献

We explore intraparticle quantum resources within a monolayer (textrm{MoS}_2) system subjected to thermal noise. Using a low-energy spin–valley effective Hamiltonian, we give the associated Gibbs density matrix and investigate the dynamics of concurrence ((mathcal {C})), local quantum uncertainty ((mathcal {L}_q)), relative entropy of coherence ((mathcal {C}_r)), and linear entropy ((mathcal {L}_e)) as functions of temperature and the two-qubit system’s parameters. Our findings reveal that entanglement vanishes at all system regimes. In contrast, quantum correlations and coherence exhibit a slightly more robust persistence under thermal noise. For high momentum components ((k_x), (k_y)) or weaker spin-orbit interaction (SOC, (lambda _s)), (mathcal {C}_r) attains relevant values at lower temperatures before decreasing as T increases. We note that, although a strong SOC suppresses coherence, it extends the temperature interval over which LQU remains slightly significant, and it is also observed to decelerate the increase in (mathcal {L}_e). These findings show that adjusting system parameters enhances thermal quantum resources in the spin-valley state of (textrm{MoS}_2) and mitigates thermal mixing.

We numerically investigate the near-infrared light absorption enhancement of a graphene monolayer, demonstrating ultra-broad bandwidth and nearly 100% electric modulation depth. This broadband absorption arises from multiple closely spaced magnetic resonance modes, which are generated by the plasmonic hybridization of silver (Ag) nanostrips and an Ag substrate. The absorption of graphene exhibits a sharp transition from its maximum value to nearly zero within a narrow Fermi energy range, enabling the exceptional modulation depth and the electric switching effect. The broadband absorption with high electric tunability can significantly enhance the performance of graphene-based optoelectronic devices, such as broadband photodetectors and high-speed modulators in optical fiber telecommunication system.

This research reported the synthesis of copper-doped zinc oxide/ carbon quantum dots (Cu-doped ZnO/CQD) nanoparticles. The chemical precipitation method was employed to prepare the nanoparticles. The role of CQD on the structural, optical, and luminescent properties of the Cu-doped ZnO is investigated. The crystallite size, strain, lattice constants and bond length are examined. The incorporation of CQD enhances the refractive index of the prepared material and reduces the optical band gap of Cu-doped ZnO. The electrochemical investigations are carried out in a three-electrode system. Impressively, the capacitive contribution increases up to 88% for Cu-doped ZnO/CQD, which was higher than the capacitive contribution of Cu-doped ZnO-based electrode. The specific capacitance of 241.6 F/g at a scan rate of 5 mV/s and 180.4 F/g at a current density of 0.5 A/g were observed. The results highlight the effective synthesis of the Cu-doped ZnO/CQD nanoparticles and their excellent electrochemical properties as a promising electrode candidate for ultracapacitor applications.

Enhancing the structural, optical and electrical properties of CuO thin films is crucial for their effective integration into modern optoelectronic devices. In this study, tin (Sn) and iron (Fe) co-doped CuO thin films were fabricated on ultrasonically cleaned glass substrates using the sol-gel spin-coating technique, with varying dopant concentrations to optimize their properties. Post-annealing characterization revealed that all samples retained a polycrystalline monoclinic CuO structure, as confirmed by X-ray diffraction (XRD). The crystallite size increased from 19 nm to 24 nm upon (Sn, Fe) co-doping, accompanied by a decrease in dislocation density from 2.34 × 10^− 3 nm^− 2 to 1.80 × 10^− 3 nm^− 2_, indicating improved crystallinity. Scanning Electron Microscopy (SEM) analysis showed increased surface uniformity following dopant incorporation. Optical analysis revealed that co-doping significantly decreased transmittance while enhancing visible light absorption. The (1.5 wt% Sn + 0.5 wt% Fe): CuO film maintained a high absorption coefficient (> 10⁵ cm⁻¹) and exhibited a reduced optical band gap of 1.43 eV, enhancing the light-harvesting capability. Hall effect measurements demonstrated that the film co-doped with 1.5 wt% Sn and 0.5 wt% Fe exhibited the lowest resistivity (28.5 Ω·cm), highest electrical conductivity (0.035 S/cm), and maximum carrier concentration (6.85 × 10¹⁷ cm^− 3), though with a reduced carrier mobility (0.304 cm²/V·s). However, further increase in Fe concentration (≥ 1 wt%) led to structural degradation under identical annealing conditions. Overall, the optimized 1.5 wt% Sn and 0.5 wt% Fe co-doped CuO thin film exhibits superior structural integrity, optical and electrical properties, demonstrating strong potential for application in future optoelectronic and photovoltaic devices.

This work investigates the subluminal and superluminal propagation of light pulses in a Combined Tripod and (varvec{Lambda })-Type (CTL) atomic medium. By analysing key parameters including normal and anomalous dispersion, group index (({varvec{n}}_{varvec{g}})), and time delay (({varvec{t}}_{varvec{d}})), we demonstrate tunable light propagation ranging from ultra-slow (({textbf {600}}~text {m/s}), (varvec{2}varvec{times } varvec{10}^{varvec{-6}}{varvec{c}})) to apparent backward superluminal ((varvec{-1000}~text {m/s}), (varvec{-3.33} varvec{times } {textbf {10}}^{varvec{-6}}{varvec{c}})) regimes. The group index tunability (({varvec{n}}_{varvec{g}} = {textbf {5}}varvec{times } {textbf {10}}^{varvec{5}}) to (varvec{-3}varvec{times } {textbf {10}}^{varvec{5}})) and corresponding time delays directly characterise the propagation dynamics, where positive ({varvec{t}}_{varvec{d}}) indicates slow light and negative ({varvec{t}}_{varvec{d}}) corresponds to fast light propagation. Such control is achieved through precise manipulation of the probe field detuning ((varvec{Delta }_{p})) in five-level, N-type, and (varvec{Lambda })-type configurations. The five-level CTL system exhibits a significantly broader tunability range—at least one order of magnitude greater than that reported in related studies (e.g., Hamedi et al, J. Phys. B: At. Mol. Opt. Phys. 50(18), 185401 2017), where they studied the subluminal propagation of light pulses, while the N-type system demonstrates both positive and negative group indices. The (varvec{Lambda })-type system, in contrast, realises ultra-slow propagation (({textbf {600}}~text {m/s})) at specific detunings. These results underline the potential of coherent atomic media for quantum optics applications, including optical buffers, quantum memory, and all-optical signal processing. The demonstrated wide-range control of light propagation speeds opens new possibilities in quantum information technologies.

Using the density of state equation derived from the type of conditions in a quantum Schrödinger well, the effect of shape on quantum confinement in semiconductor materials was used to study regular shapes to determine their effectiveness in evaluating the isometric quantum confinement of semiconductor nanocrystals.This work, in particular, examines isometric nanoparticles of various shapes and raises the question of how isometric deformation of nanoparticle shapes affects their response. The effect of quantum confinement, which includes one-dimensional, two-dimensional, and three-dimensional shapes, was investigated on three distinct shapes of semiconductor nanocrystals (rectangular, spherical, and torus) by examining the density of states of these material shapes.The analysis showed that the simplified models used for each shape indicate an inverse relationship between the ground-state confinement energy and volume. Thus, as the radius increases, the confinement energy decreases, although it never approaches zero. Further calculations revealed that the increasing variation in confinement potential corresponds to a decrease in the binding energy of the nanoparticles. Among the various shapes of equal size, nanorods exhibited lower binding energies than nanotorches, while nanotorches exhibited lower binding energies than nanospheres. These results confirm that even slight modifications in the crystal structure of nanoparticles can lead to significant changes in the properties of these nanomaterials. Theoretical results show that as the size increases, the confinement energy, Coulombic energy, and energy band gap of these quantum dots decrease.The most important result of this study is that, based on the geometry of the quantum dots studied, the sphere has the highest confinement energy, the quantum tours has the largest Coulombic energy, and the cube has the highest energy band gap. This work reveals that appropriate choices of shape and size can enhance the electronic and optical properties of nanocrystals.

We investigate the structures, electronic and magnetic properties of Fe(_{x})Ni(_{1-x}) monolayer alloys deposited on the W(110) surface (i.e., Fe(_{x})Ni(_{1-x}) /W(110)), using the density functional theory (DFT) calculations, including the effect of Hubbard correction U, i.e., DFT+U. Various combinations of ferromagnetic (FM) and ferrimagnetic (FI) orientations, including non-magnetic (NM) configurations of Fe(_{x})Ni(_{1-x}) (x varies from 0 to 1), are considered. Our calculations show that most energetically favourable configurations for the Fe-Ni alloys on the W(110) surface are when the concentration x of Ni is greater than that of Fe and where the Fe and Ni have exhibited a ferrimagnetic coupling. Also, crystal orbital Hamilton population (COHP) reveals the absence of antibonding states around the +1 eV near the Fermi energy in the case of the ground-state FI configurations and the existence of such antibonding states at the same energy level in the case of NM configurations, as the possible origin of preferred stability of the FI configuration (i.e., relative to NM). Furthermore, a comparison between the magnetization in free-standing Fe(_{x})Ni(_{1-x}) and that of Fe(_{x})Ni(_{1-x})/W(110) systems show that the W(110) substrate acts to reduce the magnetic moment of alloy atoms of Fe and Ni. This can be adduced to electron transfer between the orbitals of Fe, Ni and W atoms. Interestingly, such an electron transfer also enhances the stability of the alloys on the W(110) substrate. Our work provides deeper understanding of atomic-scale properties of Fe-Ni alloys deposited on a W(110) substrate which can be useful to understand similar epitaxial layers.

Calcium phosphate, zinc phosphate, and mixed calcium zinc phosphate glass ceramics in the systems 50CaO-50P₂O₅, 50ZnO-50P₂O₅, and xZnO.(100-x)(CaO-P₂O₅), x = 0–50 mol% have been prepared via wet-hydrothermal technique, yielding polycrystalline materials as confirmed by XRD and SEM-EDX analyses. The sharp XRD patterns correspond to crystalline Ca₃(PO₄)₂, Zn₃(PO₄)₂, and Zn₂Ca(PO₃)₂ phases in their respective systems. FTIR spectroscopy enabled calculation of relative areas proportional to different phosphate species (Qⁿ) concentrations, with peaks and relative areas corresponding to (Q⁰+Q¹) and Q² assigned using Gaussian function referencing. Physical properties including hardness, surface morphology, and density were analyzed in relation to structural changes. The substitution of CaO and P₂O₅ with ZnO increases bridging oxygen (BO) concentration up to 20 mol% ZnO, enhancing glass ceramic hardness, demonstrating ZnO’s network former role in this concentration range. Further ZnO addition (> 20 mol%) decreases BO content and hardness, indicating a transition to a modifier role. The reduction in P₂O₅ and CaO contents increases non-bridging oxygen (NBO) bonds in the phosphate network, leading to increased free volumes (Vf) and oxygen molar volume in the studied glass ceramics.

The magnetic and magnetocaloric properties of the compound Ho₂Co₃Si₅ have been thoroughly investigated. This material crystallizes in single phase with a Lu₂Co₃Si₅-type monoclinic crystal structure, belonging to the space group C12/c1, and exhibits lattice parameters of a = 10.7333(2) Å, b = 11.4132(4) Å, c = 5.4812(2) Å and β = 118.6635(3)(:^circ:). This compound exhibits antiferromagnetic behaviour with a Néel temperature, T_N = 10 K. The alloy also demonstrates a second-order magnetic behaviour with isothermal magnetization measurements revealing the presence of metamagnetic transitions. The quadratic dependence of the magnetocaloric effect on the applied magnetic field data in the paramagnetic regime suggests that the applied magnetic field plays a key role in suppressing spin fluctuations. The metamagnetic transition, along with the spin fluctuations, broadens the magnetocaloric curve, thereby enhancing the magnetocaloric effect. A maximum magnetic entropy change of 11.3 J/kg K and a relative cooling power of 226 J/kg are achieved under a magnetic field change of 5 T. Additionally, a magnetoresistance of -16% is observed at T = 2 K, at an applied magnetic field, B = 9 T. These aspects project Ho₂Co₃Si₅ as a suitable material for magnetocaloric applications.

Bulk metallic glasses (BMGs) have wide applications in aerospace, automotive power, and healthcare, and have become a new material with broad application potential. High material removal rate and high-efficiency drilling are among the main processes for creating holes with high dimensional accuracy and high casting surface quality. Poor hole quality can lead to cracks and reduced reliability. To propose a machining process suitable for amorphous alloys and achieve better drilling quality, this paper focuses on the Zr-based bulk metallic glass Zr52Cu17.5Ti16Ni12Nb2.5 as the research object. The drilling characteristics of the bulk metallic glass are studied through a combination of experiments and simulations, finding that the trends of simulation and experimental results are consistent, though the difference is around 30%. When the feed rate f = 1.2 mm/min, increasing the spindle speed reduces both axial force and torque. When the speed n is 5000 r/min, both axial force and torque increase with feed rate. By studying the effect of cutting parameters on drilling force during the machining of amorphous alloys, it is found that as the spindle speed increases from 4000 r/min to 10,000 r/min, the axial force Fz gradually decreases from the initial 47.16 N to 27.09 N, a reduction of 42.6%. The torque Mz gradually decreases from the initial 0.521 N·m to 0.355 N·m, a reduction of 31.9%. When the feed rate increases from 0.3 mm/min to 2.1 mm/min, the axial force gradually increases from the initial 33.62 N to 55.48 N, an increase of 65.0%, and the torque Mz gradually increases from the initial 0.394 N·m to 0.523 N·m, an increase of 32.7%. Through studying chip breakage and machined hole quality, it is found that as the spindle speed increases, the hole quality first improves and then deteriorates, with the highest quality achieved at a spindle speed of n = 5000 r/min. Both excessively high and low feed rate reduce hole quality, and the best hole quality at the exit is achieved at a feed rate of f = 1.2 mm/min.