Journal of the Korean Physical Society最新文献

We present an apparatus for producing ultracold Na-(^{40})K and Na-(^{41})K mixtures as a starting point for the formation of fermionic and bosonic ground-state NaK molecules. Sodium and potassium atoms are first loaded into a magneto-optical trap and transferred to an optically plugged magnetic trap, where the mixture undergoes sympathetic cooling via radio-frequency evaporation of Na. A key feature of the apparatus is its ability to switch between loading fermionic (^{40})K and bosonic (^{41})K by toggling three acousto-optic modulators. After further sympathetic cooling in an optical dipole trap, we obtain quantum-degenerate Bose–Fermi Na-(^{40})K and Bose–Bose Na-(^{41})K mixtures. This apparatus provides a robust starting point for creating ultracold Bose and Fermi gases of ground-state NaK molecules, opening pathways to explore strongly interacting dipolar quantum matter.

Dusty plasmas exhibit a rich variety of nonlinear structures, such as shock waves and solitary waves. In our research, we have delved into the evolution of multidimensional shock waves in nonuniform dusty plasmas consisting of dust grains with nonadiabatic charge fluctuation and varying sizes, electrons and ions described by a kappa distribution. To gain insights into the propagation characteristic of shock waves, the modified Korteweg–de Vries (KdV)–Burgers equation is derived by using the standard reductive perturbation technique. Numerical and theoretical analysis reveals the presence of two distinct types of shock structures within the system: oscillatory shock structures and monotonous shock structures. The findings underscore the significant impact of inhomogeneity, magnetic field, nonadiabatic dust charge fluctuation, dust size, which follows a power law distribution (PLD), and kappa indices on the behavior of shock waves. These parameters play a crucial role in shaping the characteristics and dynamics of the shock waves in dusty plasmas. The investigated results will provide a deeper understanding of the shock waves’ dynamics within such complex plasma environments.

We investigate the dynamical symmetry of the Sasaki–Mukhanov equation, which governs the evolution of primordial perturbations during inflation. By mapping the Sasaki–Mukhanov equation to a constant-frequency harmonic oscillator via an auxiliary Ermakov field satisfying the Ermakov–Pinney equation, we construct the associated sl(2, R) generators and derive the Ermakov–Lewis invariant. We apply this framework to de Sitter space and slow-roll inflation, demonstrating that the Bunch–Davies vacuum gives (I_{EL} = 1/2), conserved non-perturbatively at all orders in slow-roll.

This work presents a comprehensive theoretical study of the quantum Nernst effect (QNE) in semi-parabolic plus semi-inverse squared quantum wells (SPSSQWs) under intense electromagnetic wave (EMW) radiation, by considering both electron–optical phonon and electron–acoustic phonon scattering mechanisms. Using quantum kinetic theory, analytic expressions for the Nernst coefficient (NC) are derived through calculations of electric conductivity tensors and thermodynamic tensors. Numerical results for GaAs/AlGaAs SPSSQWs reveal complex nonlinear behaviors and multi-mode resonance effects that are strongly influenced by confinement asymmetry. Specifically, under dominant electron–optical phonon scattering, the NC exhibits pronounced nonlinear dependence on temperature, magnetic field, EMW frequency, and confinement strength. The resonance peaks are determined by the magneto-phonon resonance condition. Their positions systematically shift toward higher frequencies with increasing magnetic field, EMW frequency, or confinement frequency. Meanwhile, the background level of the Nernst coefficient decreases. In contrast, increasing temperature does not change the peak positions but enhances their amplitudes and broadens their widths. In the regime dominated by electron–acoustic phonon scattering, the QNE shows qualitatively distinct behaviors characterized by pronounced Shubnikov–de Haas (SdH) oscillations. The oscillation amplitude varies significantly with temperature, whereas the period remains nearly constant. In addition, changes in magnetic field, EMW frequency, or confinement frequency lead to simultaneous variations in both amplitude and period, with the period increasing systematically. These findings not only establish a quantitative connection between resonance peak positions and the magneto-phonon resonance condition, but also provide a unified theoretical foundation for controlled manipulation of thermomagnetic transport in SPSSQWs, supporting future experimental validation and the design of advanced thermoelectric and thermomagnetic devices.

Environmental pollution is rapidly increasing due to the growing volume of electronic waste from embedded systems. This paper addresses the challenges associated with the fabrication and modeling of next-generation non-volatile biomemristor. The Ag/Aloe vera/Cu biomemristor was successfully fabricated by utilizing a naturally derived resistive switching layer from Aloe vera fruit. The spin coater technique was used to deposit the active Aloe vera layer at 4000 rpm, yielding an average thickness of (1.6~mu m) measured by alpha-2.0 spectroscopic ellipsometer. The pinched hysteresis loop was observed, confirming the nonvolatile bipolar behavior. The physics-inspired biomemristor model is developed to complement the experimental work by simulating their I–V characteristics and underlying current conduction mechanism. The fabricated device shows a current of (pm 4 mu textrm{A}), whereas the modeled results indicate (pm 4.8 mu textrm{A}). The device exhibits stable endurance over 50 switching cycles and reliable retention up to (10^6) seconds. The analysis of the I–V of the in-house device and model revealed excellent correspondence in both high-resistance and low-resistance states. Experimental data and simulation data exhibit ohmic behavior with a slope of 1 in the low-resistance state. Additionally, the high-resistance state shows a slope of approximately 2, which supports the space-charge-limited current mechanism. Moreover, the model successfully replicates the setting and resetting voltages observed experimentally. Overall, this study highlights that organic biomaterial is a promising candidate for resistive switching devices. This research paves the path for green electronics for computing applications.

This work presents a comprehensive investigation of performance and reliability enhancement in GaN/BGaN high electron mobility transistors (HEMTs) through dual trap engineering using copper (Cu) and iron (Fe) layers on a SiC substrate. The proposed device incorporates a GaN cap, n-type BGaN barrier, BGaN spacer, and GaN channel to facilitate strong polarization-induced 2DEG formation at the heterointerface. The introduction of Cu and Fe trap layers within the buffer region is systematically analyzed using TCAD simulations to evaluate their impact on electrical, RF, and reliability characteristics. The results demonstrate a significant improvement in device performance with trap engineering. The drain current (I_DS) increases from 700 mA/mm in the conventional structure to 756 mA/mm and 784 mA/mm for Fe and Cu trap configurations, respectively. Similarly, the transconductance (g_m) improves from 130 mS/mm to 140 mS/mm and 145 mS/mm. RF performance analysis reveals variations in gate-source and gate-drain capacitances, indicating enhanced charge control and reduced parasitic effects. Notably, the minimum noise figure is reduced from 10.7 dB to 10.2 dB in the Cu trap-based device, highlighting its suitability for low-noise applications. From a reliability perspective, the peak electric field is significantly reduced in the Fe trap structure (77,514 V/cm) and remains controlled in the Cu trap case (88,480 V/cm), compared to 122,304 V/cm in the conventional device. This reduction mitigates hot carrier effects and enhances device stability. The improved performance is attributed to enhanced carrier confinement, optimized 2DEG density, and effective suppression of leakage through trap-assisted field redistribution. Overall, the proposed Cu–Fe trap-engineered GaN/BGaN HEMT demonstrates superior electrical, RF, and reliability characteristics, making it a promising candidate for next-generation high-frequency and high-power electronic applications.

In this study, we investigate a traversable wormhole solution in linear matter-curvature coupled gravity by introducing a novel hybrid shape function. The proposed model incorporates a constant redshift function and a hybrid shape function considering as (b(r) = r_{0}^{n}e^{(r_{0}-r)}r^{1-n}) where (r_0) is the throat radius. We analytically bring into existence expressions for matter distribution components, and examine the fulfillment of standard energy conditions. Notably, null, weak, and dominant energy conditions can be satisfied simultaneously for suitable choices of the coupling parameters, eliminating the need for exotic matter. Furthermore, a detailed stability analysis based on the generalized Tolman-Oppenheimer-Volkoff equation reveals balancing configurations. Our results highlight that modified gravity models, such as (f(R,L_{m},T)), offer viable mechanisms for constructing physically acceptable wormholes without violating classical energy constraints. This situation is quite remarkable as it shows that it is possible to create bridges that will provide the infrastructure in question with non-exotic matter types by revisiting the physical contribution of the relevant theory taken into account in this study in research topics that remain fantastic, since we cannot create exotic matter-like usable versions of the infrastructure required to provide important, but appropriate conditions, such as space and time travel, teleportation, transition between different space-time manifolds with today’s technologies.

We numerically investigate the features of gravitational radiation from close, fast hyperbolic encounters of two equal-mass, non-spinning black holes. We analyze angular distributions of the energy flux and its integration in time, and compare them with the predictions by mass-quadrupole calculations applied to the trajectory obtained from numerical simulation. These systems can radiate up to ({sim }{}10%) of their total energy, exceeding the 4–(5%) seen in non-spinning quasi-circular mergers and comparable to the 10–(11%) found in cases with aligned spins. The radiation is predominantly emitted toward the polar region, surpassing the equatorial direction by a factor of 4 to 9. Interestingly, as the impact parameter decreases, the energy allocation ratios toward both directions remain relatively constant and appear to approach the values of quasi-circular binary mergers at the capture threshold. In the orbital plane, the main radiation emerges at positive and negative angles near the asymptote bisector and its symmetric counterpart as generically predicted by the mass-quadrupole approximation. In the stronger-interaction regime with smaller impact parameters, however, the main radiation exhibits a longer duration, a larger angular rotation, and a narrower azimuthal spread, resulting in significant deviations from the mass-quadrupole predictions. In high-velocity encounters, the relativistic beaming effect in the Kovacs-Thorne approximation successfully captures key features of the NR radiation patterns, including the brightening of the secondary radiation profile and the narrowing of the azimuthal spread. The direction-dependent features identified here are valuable not only for exploring the fast and strong regime in general relativity, but also for improving waveform modeling and parameter estimation for hyperbolic encounter signals.

To recover a high-resolution sinogram from the original X-ray measurements, we incorporate a physics model into the upsampling process. Since the number of the pencil beams of the upsampled geometry is greater than the number of the original measurements, the information on the geometry and the statistics of the X-ray data are essential factors for a more accurate estimate. To incorporate X-ray geometric information, we propose an iterative algorithm based on a statistical learning approach comprising three steps: ray-splitting, image reconstruction, and reprojection steps. In the ray-splitting step, we estimate the high-resolution sinogram by maximizing a posteriori of the high-resolution sinogram with the original measurements and CT model. In the image reconstruction step, we reconstruct the high-resolution CT image with the estimated high-resolution sinogram. In the reprojection step, we update the statistical model of the high-resolution sinogram by reprojecting the reconstructed image for the next ray-splitting step. The performance of the proposed algorithm is demonstrated through a series of phantom experiments to evaluate the enhancement of spatial resolution in the reconstructed CT images. The results show that the statistically recovered high-resolution sinogram successfully improves spatial resolution without hardware changes.