We investigate cosmological phase transitions using the background field method (BFM) within finite-temperature quantum field theory. The one-loop thermal free energy density is calculated at high temperature and nonzero chemical potential in order to analyze spontaneous symmetry breaking in the early Universe. By constructing the effective potential in momentum space, we obtain analytical expressions and perform numerical evaluations. The results demonstrate that a first-order phase transition may occur at sufficiently high temperature and chemical potential, characterized by discontinuities in the effective scalar mass and the free energy density. Furthermore, symmetry non-restoration at high temperature is observed, suggesting a persistent asymmetry in the post-transition Universe. These findings highlight the relevance of gauge-invariant and non-perturbative methods for the study of cosmological phase transitions.
We identify the adsorbed index as an experimentally accessible order parameter for the wetting phase transition in dilute ternary Bose–Einstein condensates (BECs). By tracking the nucleation and growth of a surfactant film of the third component at the interface between two immiscible condensates, we show that the adsorbed index exhibits a logarithmic divergence with the chemical-potential ratio in the prewetting phase. Numerical Gross–Pitaevskii calculations are consistent with analytical predictions from the double-parabola approximation, confirming the reliability of the approach. Unlike the conventional surfactant layer thickness, which becomes ill-defined near the nucleation point, the adsorbed index remains well defined throughout the entire prewetting-wetting regime and is directly proportional to the number of condensed atoms in the surfactant component, a quantity that is readily measurable in ultracold-atom experiments and tunable via Feshbach resonances. Our results offer a realistic opportunity to observe wetting transitions in multicomponent quantum gases.
A nonlinear aspherical micro-lens (NAML) can be dynamically formed inside a Kerr medium under Gaussian beam (GB) illumination, providing an intensity-dependent optical surface that enables adaptive wavefront control. While previous studies have clarified the formation mechanism and spherical aberration of the NAML, the behavior of off-axis coma has not yet been fully investigated. In this work, we derive the complete third-order coma expression of the NAML by combining the nonlinear refractive-index distribution with the Seidel aberration formulation. The dependence of coma on the average laser power, nonlinear-layer thickness, and incident ray angle is examined through numerical simulations. The results show that the aspheric coma component dominates and scales strongly with , leading to substantial wavefront distortion at large power, thickness, or field angle. A practical operating window is identified in which the coma remains within a few wavelengths. These findings establish the NAML as a power-tunable micro-optical element capable of partial off-axis aberration control.
A boundary-based finite element method (BFEM) is developed for solving stress and contact problems in two-dimensional multilayered and functionally graded piezoelectric plates. In the proposed formulation, the plate is discretized into multiple material sublayers, each modeled as an individual finite element constructed solely from boundary nodes. By establishing direct relations between boundary tractions and electric displacements and nodal forces, the governing electromechanical coupling equations are transformed into a boundary-based finite element framework, thereby avoiding volumetric discretization. When contact problems are considered, the contact constraints are incorporated into the BFEM formulation through appropriate contact conditions, allowing the unknown contact regions and contact tractions to be determined as part of the solution. The proposed approach effectively accounts for multilayered configurations, functionally graded material properties, anisotropy, and electromechanical coupling effects. Numerical examples are presented to validate the method's accuracy and convergence. In addition, parametric studies are conducted to investigate the influences of material gradation and anisotropic properties on the electromechanical responses of the plates.
Abstract: This paper presents a detailed theoretical investigation of the Peltier coefficient (PC) in an infinite semi-parabolic asymmetric quantum well (ISPAQW) under the influence of an intense electromagnetic wave (EMW), considering electron-acoustic phonon scattering as the dominant scattering mechanism. By employing the quantum kinetic equation method, we have derived the analytical expressions for the conductivity tensor (), the thermoelectric tensor (), and subsequently, the PC. Numerical calculations were performed to scrutinize the complex dependence of the PC on various system parameters, including the magnetic field (B), temperature (T), EMW frequency (Ω), and confinement frequency . The results reveal that the PC exhibits distinct Shubnikov-de Haas (SdH)-like oscillations, originating from the electron-phonon interaction, as the magnetic field varies. Notably, our study demonstrates that external parameters modulate these oscillations in fundamentally different ways: Increasing the temperature T enhances the oscillation amplitude without altering the peak positions (phase). Increasing the EMW frequency strongly suppresses the amplitude and concurrently shifts the peaks toward higher magnetic fields. In contrast, increasing the confinement frequency enhances the amplitude while also shifting the peaks to higher magnetic fields. These findings provide crucial insights into the underlying physical mechanisms and the controllability of thermoelectric effects in semiconductor nanostructures. [1] F. Ioffe, L. S. Stil’bans, E. K. Iordanishvili, T. S. Stavitskaya, and A. Gelbtuch, Semiconductor Thermoelements and Thermoelectric Cooling, Physics Today, Vol. 12, No. 5, 1959, pp. 42, https://doi.org/10.1063/1.3060810. [2] T. Dien, C. T. V. Ba, N. Q. Bau, N. T. N. Anh, Calculation of Parallel Peltier Coefficient in Rectangular Quantum Wires under the Influence of Confined Optical Phonons and Electromagnetic Waves Using Quantum Kinetic Equation,Journal of the Korean Physical Society, Vol. 82, 2023, pp. 1187-1195, https://doi.org/10.1007/s40042-023-00781-2. [3] T. Hung, N. T. L. Quynh, N. T. N. Anh, N. Q. Bau, The Influence of Confined Acoustic Phonon on the Quantum Peltier Effect in Doped Semiconductor Superlattice in the Presence of Electromagnetic Wave,Journal of Physics: Conference Series, Vol. 1932, 2021, pp. 012009, https://doi.org/10.1088/1742-6596/1932/1/012009. [4] G. Gurevich, G. N. Logvinov, Physics of Thermoelectric Cooling,Semiconductor Science and Technology, Vol. 20, No. 12, 2005, pp. R57, https://doi.org/10.1088/0268-1242/20/12/R01. [5] G. Gurevich, J. E. V. Pérez,Peltier Effect in Semiconductors, (New York: John Wiley and Sons), 2014. [6] T. V. Ba, N. Q. Bau, N. T. L. Quynh, N. D. Nam, and D. T. Long, Theoretical Study of Photo-stimulated Thermo-magnetoelectric Effects in Two-dimensional Compositional Superlattices Using Quantum Kinetic Equation,Journal of the Korean Physical Society, Vol. 81, No. 8, 2022, pp. 757-769, https://doi.org/10.1007/s40042-022-00584-x. [7] Q. Bau, D. T. Hang, D. M. Quang, N. T. T. Nhan, Magneto–thermoelectric Effects in Quantum Well in the Presence of Electromagnetic Wave,VNU Journal of Science: Mathematics–Physics, Vol. 33, No. 2, 2017, pp. 1-9, https://doi.org/10.25073/2588-1124/vnumap.4071. [8] Vasilopoulos, M. Charbonneau, C. M. Van Vliet, Linear and nonlinear Electrical Conduction In Quasi-Two-Dimensional Quantum Wells, Physical Review B, Vol. 35, No. 3, 1987, pp. 1334, doi.org/10.1103/PhysRevB.35.1334. [9] T. Huong, N. Q. Bau, C. T. V. Ba, B. T. Dung, N. C. Toan, A. T. Tran, Theoretical Study of Magnetoresistance Oscillations in Semi-parabolic Plus Semi-Inverse Squared Quantum Wells in the Presence of Intense Electromagnetic waves, Phys. Scr., Vol. 100, 2024, pp. 015984. Q. Bau, N. T. H. Anh, D. V. Toan, N. T. Long, Effect of Electron-Confined Optical Phonon Scattering on the Ettingshausen Effect in GaAs/AlAs Quantum Well With Parabolic Potential Under Laser Radiation, Commun. Phys., Vol. 31, 2021, pp. 101. Vasilopoulos, Magnetophonon Oscillations in Quasi-two-dimensional Quantum Wells, Physical Review B, Vol. 33, 1986, pp. 8587. V. Paranjape, J. S. Levinger, Theory of the Ettingshausen Effect in Semiconductors, Phys. Rev., Vol. 120, 1960, pp. 437. N. Q. Bau, D. T. Hang, D. T. Long, Study of the Quantum Magneto-thermoelectric Effect in the Two-Dimensional Compositional Superlattice Gaas/Algaas under the Influence of an Electromagnetic Wave By Using the Quantum Kinetic Equation, J. Korean Phys. Soc., Vol. 75, 2019, pp. 1004-1016. K. Ridley, Quantum Processes in Semiconductors, Pub. Clarendon Press, Add. Oxford, 1993. Jasprit Singh, Physics of Semiconductors and Their Heterostructures, Pub. McGraw-Hill, Add. Singapore, 1993
The relationship between structure and density in Al2O3 glass has been studied by mean of molecular dynamic simulation. Simulation results reveal that the structure of Al2O3 is formed by AlOx structural unit. Under densification, there is the transformation from tetrahedral to octahedral structure. The AlOx structural units tend to form the cluster of AlOx units. Alumina exhibits polymorphism and heterogeneous structure due to the presence of AlOx clusters and two-domain types (D4–D5 or D5–D6) in the intermediate density range. Moreover, a continuous random network of basic structural units linking to each other via with corner-sharing, edge-sharing, face-sharing bond. At low density region, the basic structural units are mainly linked via bridge oxygen and the connectivity between AlOx is mainly corner sharing bonds. The numbers of corner-sharing and edge-sharing bonds vary in opposite directions. The basic structural units are barely bonded to each other via face-sharing bond. In the model, there is the existence of the free volume region. The distribution of free volumes depends on density. It has the Gaussian form and the position of the peak tends to shift to the left under compression. As densnit increases, the void radius decreases rapidly.
This study reports the synthesis and characterization of ZnO/NiFe2O4 nanocomposites for potential application in photocatalytic wastewater treatment. The composites were prepared via a two-step hydrothermal process with Zn²⁺/Ni²⁺ molar ratios of 1, 1.5, and 2. X-ray diffraction combined with Rietveld refinement confirmed the coexistence of characteristic crystalline phases with nanoscale particle sizes. SEM observations revealed distinct morphologies. Magnetic characterization using a vibrating sample magnetometer indicated that pure NiFe2O4 exhibited soft magnetic behavior, while the saturation magnetization of the composites decreased as ZnO content increased. UV–Vis spectroscopy and band gap analysis demonstrated an extension of optical absorption from the ultraviolet to the visible region. These properties suggest that ZnO/NiFe2O4 composites may serve as potential candidates for magnetically recoverable photocatalysts, although photocatalytic performance evaluation will be the subject of future work.
We investigated control of optical bistability behavior based on the probe absorption and Kerr nonlinearity properties in a tripod-type degenerate four-level atom system under an external magnetic field. This excitation configuration can provide two transparent spectral regions on the probe absorption profile. It can be transitioned between the transparency and absorption regimes by turning on or off the magnetic field in different frequency domains. We can effortlessly transform one into two transparency windows, and vice versa, by modifying the intensity of the magnetic field. The investigations showed the enhancement of the Kerr nonlinearity around one/two-EIT windows, thereby forming one/two-channel optical bistability in these frequency regions. In addition, the coupling field intensity, the probe frequency detuning, and the atomic cooperation parameter have also significantly influenced the absorption spectrum, Kerr nonlinearity, and optical bistability. The proposed model has useful applications for storage and optical switching, and nonlinear logic gates in optical communications processing.
We theoretically investigate the thermomagnetic Nernst effect in an infinite semi-parabolic asymmetric quantum well under the influence of a high-frequency electromagnetic wave. By using the quantum kinetic equation method, we derive analytical expressions for the Nernst coefficient, taking into account the electron-acoustic phonon interaction as the primary scattering mechanism. Numerical results show that the Nernst coefficient exhibits distinct Shubnikov-de Haas oscillations due to Landau quantization. We analyze in detail the dependence of the Nernst coefficient on temperature, magnetic field, confinement frequency, and electromagnetic wave frequency. A key finding is the contrasting influence of thermal and electromagnetic parameters: while increasing temperature significantly suppresses the oscillation amplitude via thermal broadening without affecting the peak positions, the presence of a high-frequency electromagnetic wave not only dampens the amplitude but also induces a shift in the resonance peaks. Additionally, the Nernst coefficient is found to be enhanced by a stronger confinement potential. These results suggest that the thermomagnetic properties of an infinite semi-parabolic asymmetric quantum well can be effectively tuned by external fields, offering potential applications in low-temperature nanodevices.
Ag - SiO2 nanocomposite material was synthesized by the Stöber method and reduction process. SEM images showed that SiO2 in the form of a nanosphere, and an average particle size of 165 nm, and Ag nanoparticles possess an average particle size of 17 nm, distributed quite evenly on the surface of SiO2 nanospheres. The UV - Vis absorption spectrum of Ag - SiO2 material presents a broad band at 400 nm attributed to plasmon surface resonance of Ag nanoparticles. Mixing up solutions of Ag - SiO2 and R6G, a fluorescence band of Rhodamine 6G (R6G) at 570 nm increased 86 times compared with that of only R6G. The as-prepared Ag - SiO2 nanocomposite material also increased the fluorescence intensity of R6G with concentration varying from 0.1 to 100 ppm.
In this study, hydroxyapatite (HA) coatings were synthesized on titanium substrates using the plasma electrolytic oxidation (PEO) technique to enhance corrosion resistance and improve the biocompatibility of implant materials. The experiments were conducted in an electrolyte containing calcium acetate hydrate and sodium dihydrogen phosphate monohydrate under a constant voltage of 500 V, with treatment durations of 1, 3, 5, and 7 minutes. The surface morphology and structural characteristics of the coatings were analyzed using various characterization techniques. X-ray diffraction (XRD) results revealed the distinct formation of hydroxyapatite phases when the treatment duration reached 7 minutes. Scanning electron microscopy (SEM) observations showed a uniformly porous surface morphology while energy-dispersive X-ray spectroscopy (EDS) confirmed the presence of calcium and phosphorus elements. Furthermore, corrosion performance evaluated in simulated body fluid (SBF) using Tafel polarization curves demonstrated that the PEO-coated samples exhibited significantly higher corrosion potentials and polarization resistance than bare titanium, indicating superior surface protection. In vitro cell culture experiments using BHK cells for 48 h and 72 h confirmed good cell attachment and proliferation on the HA-coated surfaces. These results demonstrate that hydroxyapatite coatings prepared by the plasma electrolytic oxidation method hold great potential for biomedical implant applications.
The yttrium iron garnet (YIG) material doped with molybdenum (Mo⁵⁺) with the composition Y3Fe4.96Mo0.04O12 (x = 0.04) was synthesized using a sol-gel method combined with thermal treatment. The resulting powder had a single-phase structure, high crystallinity, and a uniform microstructure. Morphological, structural, and electrical characteristics of the material were investigated using XRD, SEM, FTIR, and I–V measurements. A bolometer device was fabricated by depositing the YIG sensing layer onto an interdigitated Pt electrode array. Photo-current, responsivity (Ri), noise equivalent power (NEP), and specific detectivity (D*) measurements were performed in the ultraviolet–visible–near-infrared (UV–VIS–NIR, 281–1010 nm) range. The x = 0.04 sample yielded an activation energy of 0.32 eV, a TCR of 3.9 %K⁻¹, a photo-current of ~106 µA, and a responsivity of 848 mA/W. The NEP and D* values were suitable for a sensor operating at room temperature without the need for cooling. The results were compared with other doped YIG samples such as Y3Fe4.9Ni0.08O12 and Y3Fe4.9Mo0.1O12, which showed that the x = 0.04 sample achieved an optimal balance between thermal sensitivity and electrical insulation, promising for bolometer applications in a wide spectral range.
In this study, Co3O4 nanostructures were synthesized by hydrothermal method through a two-step process including hydrothermal followed by heat treatment. The hydrothermal conditions, such as temperature and time, were varied to obtain the morphological characteristics of the Co3O4 nanostructures. The morphological and structural characteristics were analyzed by techniques such as field-effect scanning electron microscopy (FESEM) and X-ray diffraction (XRD). Our findings reveal that the nanostructures exhibit diverse morphologies, depending on the hydrothermal conditions. In addition, we investigated the gas sensing capabilities of the nanosheets to ammonia.
This paper reports the criticality calculations of the Dalat Nuclear Research Reactor (DNRR) with low enriched uranium fuel using the MCNP6.3 code and the newly released ENDF/B-VIII.1 data library. The work aims to evaluate the effect of the ENDF/B-VIII.1 data library on the criticality analysis of the DNRR and compared to previous libraries ENDF/B-VIII.0 and JENDL-5. The calculations were conducted based on ten criticality conditions of the core consisting of 92 LEU fuel bundles, and compared against measurement and with that obtained with previous versions of data libraries. A tendency was observed that ENDF/B-VIII.1 yields higher keff values compared to ENDF/B-VIII.0, with the largest discrepancy of 150 pcm, but closer to JENDL-5. The deviation compared to the experiments is from -111 to +145 pcm. This discrepancy indicates a generally good agreement between calculations and measurements, and among the three latest libraries.This paper reports the criticality calculations of the Dalat Nuclear Research Reactor (DNRR) with low enriched uranium fuel using the MCNP6.3 code and the newly released ENDF/B-VIII.1 data library. The work aims to evaluate the effect of the ENDF/B-VIII.1 data library on the criticality analysis of the DNRR and compared to previous libraries ENDF/B-VIII.0 and JENDL-5. The calculations were conducted based on ten criticality conditions of the core consisting of 92 LEU fuel bundles, and compared against measurement and with that obtained with previous versions of data libraries. A tendency was observed that ENDF/B-VIII.1 yields higher keff values compared to ENDF/B-VIII.0, with the largest discrepancy of 150 pcm, but closer to JENDL-5. The deviation compared to the experiments is from -111 to +145 pcm. This discrepancy indicates a generally good agreement between calculations and measurements, and among the three latest libraries.
In this study, the Statistical Moment Method (SMM) is applied to investigate the structural properties of the W-Fe alloy at temperatures up to 3000 K and pressures up to 20 GPa. Analytical expressions for the free energy are derived, along with explicit formulas for structural quantities such as lattice constants and volume, taking into account the effects of anharmonicity. The results obtained from the SMM show good agreement with existing theoretical calculations and experimental data. This method demonstrates strong potential for further extension to the study of elastic properties, thermodynamic quantities, and the melting temperature of the W–Fe alloy in future work.
In this study, the physical characteristics of the hexagonal closed-packed structure's Mg2La, Mg2Nd, and Mg2Sm (C14) phases at 300 K have been examined. The L-J potential approach was used to compute SOECs and TOECs. The obtained SOECs and TOECs are utilized to assess mechanical characteristics at various angles along the unique axis. Thermophysical properties of the material at 300K have been evaluated, such as energy density, thermal conductivity, Debye temperature, and Debye average velocity of selected materials. Beyond this, we have computed the ultrasonic acoustic coupling constant at room temperature. Ultimately, the thermoelastic relaxation process and phonon-phonon interaction are used to obtain attenuation. The obtained results have been compared with previous research on similar kinds of HCP metal.
Theoretical study of the Hall effect in an infinite semi-parabolic Quantum Well (ISPQW) in the presence of electromagnetic using the quantum kinetic equation in the case of electron-acoustic phonon scattering. With the quantum kinetic equation method, the electron distribution function is constructed, from which analytic expressions for the conductivity tensor and the Hall coefficient are derived. The results reveal that the Hall coefficient exhibits a nonlinear dependence on temperature T, magnetic field B, electromagnetic wave frequency , and confinement frequency . Numerical calculations are carried out for a GaAs/AlGaAs quantum well, analyzing the influence of external fields and confinement parameters. Notably, the presence of the electromagnetic wave induces quantum oscillations of the Shubnikov–de Haas type and reduces the average value of the Hall coefficient at high magnetic fields. The results contribute to a deeper understanding of the quantum nature of the Hall effect in asymmetric quantum systems and expand the potential applications of low-dimensional semiconductor structures in advanced nanoelectronic and quantum technologies.
We investigate the effects of axion-like particle and anomalous triple gauge couplings in production, followed by the leptonic decay of the Z boson with the center – of – mass energy and the polarized initial beams. We consider the contribution of axion-like particle, photon, and Z boson propagators. We find the mass of axion like particle to enhance the cross-section in case of axion-like particle propagator. The results indicate that with the anomalous coupling , the cross-section is larger than that with the axion-like particle and photon propagators under the same conditions.
The temperature dependence of the magnetic moment in La(Fe1-xSix)13 compounds reveals the presence of both first-order and second-order magnetic phase transitions. The nature of the transition is governed by variations in the Si concentration, which induce significant modifications in the FeI–FeII interactions between Fe atoms occupying two non-equivalent sites. These effects can be effectively modeled as a form of random anisotropy, the resulting behavior of which is accurately described within the framework of the Blume-Capel model. Monte Carlo simulations demonstrate that the evolution from a first-order to a second-order magnetic transition in La(Fe1-xSix)13 compounds can be consistently reproduced by maintaining a fixed anisotropy probability p while systematically reducing the corresponding anisotropy amplitude D, yielding good agreement with experimental trends.
