Journal of the Korean Physical Society最新文献

We examined the half-filled disordered Hubbard model with repulsive interaction on a two-dimensional square lattice using the semiclassical approximation (SCA) method. In the absence of disorder, the system becomes a antiferromagnetic (AF) Mott insulator in the strong interaction regime. However, when on-site random potentials are introduced, the AF order is suppressed, and the system can transition into an Anderson insulating phase at sufficiently strong disorder. To distinguish between the AF Mott insulator and the Anderson insulator, we computed the AF order parameter (langle m rangle) and its fluctuation (langle alpha rangle) across varying disorder strengths and temperatures. Our results show that (langle m rangle) exhibits a monotonic decrease with increasing disorder strength, although it drops sharply near the transition point. In contrast, the fluctuation (langle alpha rangle) displays nontrivial, non-monotonic behavior, particularly at intermediate disorder strengths. These features are related to variations in the effective density, as determined by the maximum Matsubara frequency used in the SCA calculations. We interpret this non-monotonic behavior of (langle alpha rangle) as a potential signature that distinguishes the AF Mott insulating phase from the Anderson insulating phase. Finally, we investigated the behavior of both (langle m rangle) and (langle alpha rangle) as functions of temperature. We found that, at low temperatures, disorder-induced charge fluctuations suppress the AF order more effectively than thermal fluctuations.

The structural, thermal, and magnetic properties of Fe_84-xCo_xTi₇Zr₆B₃ (x = 0, 10, 20, 30) amorphous alloy ribbons were investigated. All alloys showed a low coercivity (H_C) of less than 20 A/m. As the Co content increased, the saturation magnetization (M_S) tended to increase. In addition, increasing the Co content effectively suppressed the formation of the second crystallization phase, which deteriorates magnetic properties. To further improve the magnetic properties, annealing was performed at several temperatures for 10 min. Especially, after annealing at 520 °C, all alloys exhibited lower H_C than the as-spun ribbons. In addition, Fe₇₄Co₁₀Ti₇Zr₆B₃ showed an increase in M_S of about 20 emu/g, while maintaining a H_C of less than 10 A/m after the 550 °C heat treatment. This study contributes to the development of Fe-based amorphous alloys with enhanced soft magnetic properties, which are essential for future energy technologies.

Jet flavor tagging, the identification of jets originating from c-quarks, b-quarks, and other quarks (light quarks and gluons), is a crucial task in high-energy heavy-ion physics, as it enables the investigation of flavor-dependent responses within the hot and dense nuclear medium produced in heavy-ion collisions. Recently, several methods based on deep learning techniques, such as deep neural networks and graph neural networks, have been developed. These deep-learning-based methods demonstrate significantly improved performance compared to traditional methods that rely on track impact parameters and secondary vertices. In the tagging algorithms, various properties of jets and constituent charged particles are used as input parameters. We explore a new method based on images surrounding the primary vertex, utilizing charged particles within the jet cone, which can be measured using a silicon tracking system. For this initial experimental study, we assume the ideal performance of the tracking system. To analyze these images, we employed convolutional neural networks. The image-based flavor tagging method shows an 80–90% b-jet tagging efficiency for jets in the transverse momentum range from 20 to 100 GeV/c. This approach has the potential to significantly improve the accuracy of jet flavor tagging in high-energy nuclear physics experiments.

In this study, Bi-2212 superconductor ceramics with Pr doping in the composition of Bi₂Sr₂Pr_xCaCu₂O_8+δ (x = 0.0; 0.1; 0.2; 0.3) were synthesized by the sol–gel method. An investigation was conducted to examine the effect of Pr doping on the structural, microstructural, and magnetic properties. X-ray diffraction (XRD) analysis demonstrated that the primary phase of Bi-2212 exhibited a decline in strength with increasing Pr doping, concomitant with the formation of secondary phases, including PrO₂ and Bi-Sr-Ca oxides, within the structural arrangement. Scanning electron microscopy images revealed that the porous and heterogeneous microstructure observed in the undoped sample transformed into a more compact yet phase-separated texture with high Pr doping. Magnetic measurements reveal a distinct magnetic transition from a superconducting state to a paramagnetic state. The undoped sample exhibited a superconducting transition at approximately 85 K. It demonstrated a critical current density (J_c) of 8.7 × 10⁴ A/cm² at self-field at 10 K. Conversely, no superconducting transition was observed in the Pr-doped samples. The results obtained demonstrate that Pr doping disrupts the structural stability of the superconducting phase, promotes paramagnetic behavior through magnetic Pr³⁺ ions and secondary phase formation, and ultimately suppresses superconductivity.

Efficient real-time data processing in modern AI and IoT devices requires ultra-low-power consumption and minimal latency. Flip-flops (FFs), being fundamental sequential elements, play a crucial role in determining system performance and energy efficiency. This work presents a novel Negative-Edge Triggered True Single-Phase Clocked Flip-Flop (NET-TSPC-FF) implemented using a 7 nm FinFET process. The proposed design is evaluated across a wide temperature range to investigate the impact of the Temperature Inversion Effect (TIE), a phenomenon in advanced FinFET technologies where delay and power exhibit a reverse trend compared to conventional CMOS devices. Simulation results demonstrate that the FinFET-based NET-TSPC-FF achieves significantly lower latency of 12.72 ps using 7 nm FinFET process compared to 27.95 ps using 22 nm CMOS at 300 K and reduced power consumption of 0.86 μW using 7 nm FinFET process compared to 5.19 μW using 22 nm CMOS. Furthermore, under higher temperatures (380 K), latency in FinFET-based FFs continues to improve while CMOS counterparts degrade, highlighting the influence of TIE. Overall, the proposed design demonstrates superior performance, validating its suitability for ultra-low-power, high-speed AI, and IoT applications.

Based on the Darwin’s Hamiltonian, the many-particle quantum hydrodynamics (QHD) is considered. A thorough investigation is conducted into the force field emerging in the associated Euler equation, meticulously tracing the contributions of various terms within Darwin’s Hamiltonian to the Euler equation. The non-linear reductive perturbation technique is employed to derive Korteweg–De Varies (KdV) equation and soliton solution is obtained. The impact of various parameters, e.g., particle concentration, Darwin interaction, and propagation speed of soliton, is studied. We noted significant impacts on both the width and amplitude of the soliton, providing insights into the intricate interaction between quantum relativistic effects and soliton properties.

We present the synthesis and comprehensive characterization of SiO₂-coated CaTiO₃:Yb³⁺,Er³⁺ upconversion phosphors (CaTiO₃:Yb³⁺,Er³⁺@SiO₂ UCPs). The core CaTiO₃:Yb³⁺,Er³⁺ particles were fabricated via a high-energy wet ball-milling method, followed by surface modification with a SiO₂ shell. X-ray diffraction (XRD) analysis confirmed that the diffraction patterns of the synthesized samples matched well with those of the orthorhombic CaTiO₃. Transmission electron microscopy (TEM) revealed a uniform silica coating surrounding the CaTiO₃:Yb³⁺,Er³⁺ cores with a thickness of a few nanometers. Under 980 nm excitation, the photoluminescence spectra exhibited strong green emissions corresponding to the ⁴S_3/2/²H_11/2 → ⁴I_15/2 transitions and weaker red emission from the ⁴F_9/2 → ⁴I_15/2 transition. Cytotoxicity evaluation using MDA-MB-231 breast cancer cells showed over 80% viability at a sample concentration of 40 μg/mL after 48 h, indicating good biocompatibility. These results suggest that CaTiO₃:Yb³⁺,Er³⁺@SiO₂ UCPs are promising candidates for bioimaging applications.

In this study, we demonstrate the sensing of refractive index through asymmetric surface lattice resonances (a-SLRs) in an array of gold nanodisks (AuNDs), showing significant alterations in transmission spectra at the a-SLRs and the shift of resonance wavelengths in response to changes in the refractive index of the surrounding media. We investigate the sensitivity of our approach by utilizing a water-glycerol mixture with different composition ratios, illustrating that the AuND array with the a-SLRs exhibits twice the sensitivity compared to the single AuND relying on localized surface plasmon resonance. Furthermore, the angle-dependent transmission spectra are examined to assess the feasibility of the AuND array with the a-SLRs for sensing applications.

This paper describes a modified plasma electrode (PE) configuration for an Accel–Decel ion extraction system aimed at enhancing ion beam optical quality. The conventional linear PE is replaced by a curved profile based on a hyper­bolic tangent function, and its influence on beam emittance and extracted current is studied systematically using the IBSimu simulation. The reference design is a 2.45 GHz electron cyclotron resonance (ECR) proton source originally with a linear PE structure. A new curved geometry parameterized by the adjustable curvature factor b is conceived and thoroughly studied. The simulation results indicate that the new structure reduces the root-mean-square (RMS) emittance by more than five orders of magnitude from the conventional linear geometry with relatively comparable beam current. Besides, the effect of PE aperture diameter on beam quality is also studied. These findings present important guidelines for the design of high-performance ion extraction systems with improved beam quality and preserved current efficiency.