物理最新文献

As optical soliton propagates in optical fiber system, higher-order dispersion plays an important role when optical soliton’s higher-order dispersion length is less than or equal to second-order dispersion length. In this study, a chirped Gaussian soliton with consideration of third-order dispersion is theoretically modulated, in a single-mode optical fiber system. Six different parameters of the propagated chirped Gaussian soliton are varied, to modulate input soliton’s temporal and frequency properties. Output pulse shapes and optical spectra that after modulation have unique variation characteristics in orthogonally polarized directions, as different soliton parameters change. For example, it is found that through changing propagation distances and pulse chirps of separated orthogonal components, oscillated pulse tails may occur for both output orthogonal components. Orthogonal output optical spectra maintain their states under the variations of propagation distances, while obvious changes (peak intensities and bandwidths) may occur for output orthogonal optical spectra when pulse chirps change. This study further explores the influence of higher-order dispersion on extra-cavity modulating solitons that propagate in nonlinear optical systems.

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Sb₂S₃ is a promising eco-friendly semiconductor for high-performance solar cells, however its potential is limited by growth orientation-induced non-radiative recombination and carrier scattering. In this study, the growth parameters of Sb₂S₃ films are compared to those of traditional and seeding-assisted spin-coating techniques, and a growth mechanism is proposed. In-depth investigations are performed to identify how annealing temperatures, spin-coating cycles, and seeding-layer concentration affect the microstructure, crystallinity, preferred orientation, optical characteristics, and photovoltaic performance. X-ray diffraction data showed that adding a seeding layer promotes the growth of Sb₂S₃ crystallites with [hk1] orientation while reducing the undesirable [hk0] orientation. Morphological investigations showed that the seeding-assisted approach promotes grain growth, film compactness, and structural consistency. Additionally, a qualitative growth mechanism based on critical particle size (r₀) and interfacial binding energy is proposed to better understand orientation transition behavior. The seeding layer enhances interfacial contacts between the seed and absorber layers, increasing r₀. For Sb₂S₃ films formed on FTO substrates, the crystallite size is predicted to be 15 nm. The increased crystallite size and steady growth of strongly [hk1]-oriented Sb₂S₃ films lead to improved charge transport characteristics, reduced carrier recombination, and enhanced optical absorption. As a result, the corresponding solar cells show increased photovoltaic performance, notably in terms of fill factor and open-circuit voltage. This study provides a simple and scalable method to improve the performance of solution-processed Sb₂S₃ solar cells, as well as valuable insights into orientation engineering and growth regulation of quasi-one-dimensional chalcogenide semiconductors.

A coupled phase-field/lattice Boltzmann (PF-LBM) framework was employed to investigate the migration, deformation, and entrapment of initially prescribed bubbles during dendritic solidification of an Al–4.5 wt.% Cu alloy. Solidification experiments combined with scanning electron microscopy (SEM) and X-ray computed tomography (XCT) were performed to characterize the pore morphologies and provide experimental comparison with the numerical predictions. The interactions between dendritic growth and the migration and entrapment of pre-existing bubbles under convective conditions were examined. The interactions between bubble dynamics and dendritic growth in multiphase flow were simulated using a coupled Shan–Chen multiphase flow model and a phase-field lattice Boltzmann (PF-LBM) model. The buoyancy-driven behaviors of bubbles, including rising, deformation, breakup, and coalescence, were found to be strongly influenced by the melt Reynolds number(Re) and Eötvös number(Eo). A reduction in surface tension significantly intensified bubble deformation. During the interaction between bubbles and dendrites, the migration velocity of bubbles gradually decreased and eventually approached zero due to the blocking effect of the growing dendrites, accompanied by pronounced changes in bubble morphology. Furthermore, the coupled evolution behavior of bubbles and dendrites in multiphase flow was strongly dependent on the solidification mode. Under equiaxed solidification conditions, bubbles were confined within interdendritic spaces and exhibited isolated, nearly spherical morphologies as a result of the spatial constriction imposed by multidirectional dendritic growth. In contrast, under columnar solidification conditions, bubbles migrated along the direction of heat flow, where they were pushed and eventually captured by dendrite tips, leading to the formation of elongated pore morphologies aligned with the dendritic growth direction. SEM and XCT observations further revealed isolated and randomly distributed pores within the equiaxed dendritic structure, whereas elongated and directionally distributed pores were observed within the columnar dendritic structure. Quantitative XCT analysis further revealed estimated mean pore sphericities of 0.76 and 0.66 within the equiaxed and columnar dendritic structures, respectively. These experimental findings support the distinct morphological trends predicted by the numerical simulations.

Exploring novel two-dimensional (2D) carbon allotropes, as well as clarifying the relationship between distinctive networks and associate properties, are essential for the development of next-generation carbon-based nanodevices. Herein, a novel 2D carbon allotrope with periodically arranged tetragonal and hexagonal carbon rings is theoretically predicted and named TH-C16. This new carbon allotrope possesses a distinct buckled morphology, stemming from the sp³-hybridized carbon atoms. The robust structural stability of the TH-C16 framework is comprehensively validated via cohesive energy calculations, phonon dispersion analysis, mechanical elastic constant evaluation, and ab initio molecular dynamics simulations. Owing to the anisotropic geometry, TH-C16 exhibits orientation-dependent mechanical behaviors and displays either brittle or ductile features under different in-plane strain directions. Moreover, TH-C16 is intrinsically metallic, with electronic states near the Fermi level predominantly contributed by carbon atoms within sp²-hybridized tetragonal rings. Compressive strain can induce an indirect bandgap in this 2D carbon framework, whereas substituting the sp²-hybridized tetragonal carbon rings with BN units yields a wide direct bandgap. Furthermore, both the pristine all-carbon network and its semiconducting BN-doped derivative exhibit notable optical anisotropy within the visible-light spectrum. This work not only enriches the family of 2D carbon allotropes but also provides promising material candidates for the design and fabrication of advanced carbon-based nanoelectronic and optoelectronic devices.

We explore the properties of quark stars by combining the microscopic axion-extended Polyakov–Nambu–Jona-Lasinio model with the macroscopic framework of four-dimensional Einstein–Gauss–Bonnet (4D EGB) gravity. Specifically, axion effects are incorporated through the background phase (theta =a/f_a) in the thermodynamics of quark matter. Our results show that the inclusion of axion-induced interactions stiffens the quark-matter equation of state, thereby increasing the sound speed and the maximum mass of quark stars. The 4D EGB correction effectively weakens gravitational compression and further modifies the stellar structure, allowing for larger radii and higher maximum masses while reducing the compactness and the surface gravitational redshift. The combined effects can support quark stars above (2,M_odot ,) with mass–radius sequences overlapping the observational regions in the indicative phenomenological comparison. These findings reveal that the interplay between axion-induced modifications of dense quark matter and 4D EGB gravity may provide a viable phenomenological framework for describing massive quark stars.

Organic–inorganic metal halide (OIMH) perovskite single crystals have emerged as promising materials for next-generation photovoltaic applications owing to their superior optoelectronic properties and reduced defect density compared to thin-film counterparts. In this study, the structural, optical, thermal, and mechanical properties of MAPbI₃ and mixed-cation FA₀.₈₅MA₀.₁₅PbI₃ single crystals were systematically investigated. The crystals were synthesized using inverse temperature crystallization and modified inverse temperature crystallization methods. UV–Vis spectroscopy revealed optical band gaps of approximately 1.45 eV for MAPbI₃ and 1.44 eV for FA₀.₈₅MA₀.₁₅PbI₃, indicating their suitability as efficient solar absorbers. Photoluminescence analysis demonstrated enhanced emission intensity and reduced defect density in the mixed-cation crystal. Thermogravimetric analysis showed improved thermal stability for FA₀.₈₅MA₀.₁₅PbI₃, which remained stable up to 282 °C, compared to 215 °C for MAPbI₃. Scanning electron microscopy confirmed the formation of high-quality grain-boundary-free single crystals with excellent crystallinity. Nanoindentation measurements revealed orientation-dependent mechanical behavior in MAPbI₃, with Young’s modulus values of 18.18 ± 1.23 GPa and 17.58 ± 2.01 GPa for the (100) and (112) planes, respectively. The mixed-cation FA₀.₈₅MA₀.₁₅PbI₃ exhibited higher stiffness and hardness, with a Young’s modulus of 21.16 ± 6.23 GPa and hardness of 1.04 ± 0.23 GPa. Energy-based fracture toughness analysis indicated enhanced crack resistance in the mixed-cation crystal. Furthermore, load-dependent, and creep nanoindentation studies revealed significant indentation size effects and time-dependent deformation. These findings provide comprehensive insights into the mechanical reliability of perovskite single crystals and highlight the advantages of cation engineering for durable and high-performance perovskite solar cells.

Iron-oxide nanoparticles (IONPs) were prepared from Indonesian iron sand using high-energy ball milling (HEBM) for 3 and 6 h. The structural, morphological, and magnetic properties of the resulting IONPs were investigated using XRD, TEM, FTIR, FESEM, and VSM. The XRD patterns exhibited major reflections consistent with a magnetite-type spinel iron-oxide structure, while weak additional reflections could not be assigned unambiguously to a distinct iron-oxide phase using conventional XRD alone. The Scherrer-estimated crystallite size decreased from approximately 30 nm to 25 nm with increasing milling duration. TEM revealed apparent particle sizes of approximately 8 and 5 nm for the 3 and 6 h samples, respectively, with an approximately spherical morphology and a tendency toward agglomeration. The FTIR spectra exhibited Fe–O vibrational bands in the low-wavenumber region. The saturation magnetization (M_s) increased from 49.53 to 73.90 emu g^− 1, while the coercivity (H_c) increased from 107.87 to 151.80 Oe with increasing milling duration. Overall, the results demonstrate milling-duration-dependent changes in the structural, morphological, and room-temperature magnetic characteristics of the IONPs derived from Indonesian iron sand.

FeNiMn and FeNiMnSiGe thin-film alloys were prepared by magnetron co-sputtering under identical technological conditions in order to establish how the addition of the metalloids Si and Ge affects their microstructure, surface morphology, and strain-gauge properties. TEM, SAED, XRD, and AFM were used to analyze crystal structure and surface morphology. Electromechanical testing over the strain ranges ε_l1 = 0–1% and ε_l2 = 0–2% reveals that Si and Ge suppress the mechanical hysteresis and the baseline resistance drift typical of the base ternary FeNiMn thin-film alloy and extends the highly reversible electromechanical response up to 2% strain, while the gauge factor decreases from 7.68 to 1.25 and from 13.75 to 2.50 for the two ranges, respectively. Cyclic loading at 100 °C causes a temporary resistance drift during the first cycle but may be related to partial relaxation of residual growth stresses: after cooling to room temperature, the Fe₂₂Ni₂₀Mn₂₂Si₁₅Ge₂₁ film exhibits a closed hysteresis loop, a strictly linear response, and stable gauge factors of 1.33 and 1.47 with negligible baseline drift. The combination of linearity, cyclic stability, and thermal endurance makes highly doped FeNiMnSiGe films promising sensitive elements for precision strain sensors.

The growth and characterization of single crystalline materials require considerable experimental expertise and cumbersome evaluation. Estimating the physical properties of single crystals from their polycrystalline counterparts is a topic of considerable scientific interest. A close agreement between elastic theory-derived zero-porosity-corrected values of longitudinal (L₀) and rigidity modulus (G₀) for polycrystalline Y₃Fe₅O₁₂ and longitudinal (C₁₁) and shear (C₄₄) stiffness constants for single crystalline equivalent has been found. This prompted the approximation of elastic, magnetoelastic, and magnetostriction constants for single crystalline analogs of the garnet series Y_3-xFe_5+xO₁₂, with x = 0.0, 0.1, 0.3, and 0.5. The elastic stiffness constants (C₁₁, C₁₂, and C₄₄), magnetoelastic coupling constants (b₁ and b₂), and interatomic force constant (f) are found to decrease. The elastic compliance constants (S₁₁, S₁₂, and S₄₄) are found to increase while magnetostriction constants (λ₁₀₀, λ₁₁₁, λ₁₁₀) and λ_S show random variations with Fe³⁺ substitution. The Cauchy pressure (P_c) monotonically increases for x = 0.1–0.5 compositions. The results have been explained based on the large size and magnetic moment mismatch of Y³⁺ (0.89 Å, 0 μ_B)- and Fe³⁺ (0.645 Å, 5 μ_B)-induced structural and electronic distortions, lattice strain, and antisite disorder. In addition to qualitative analysis, quantitative analysis to explain the variation of λ₁₁₁ and f versus x has been given.

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