Journal of the Korean Physical Society最新文献

This article investigates the performance of a 14 nm gate length heterostructure Si_0.5Ge_0.5/Si junctionless gate-all-around (SiGe-JLGAA) device employing SILVACO ATLAS 3D simulator. The proposed device is analyzed in three configurations: underlap, fit, and overlap, and they are compared to a conventional entire region silicon JLGAA structure. First, the choice of x = 0.5 for Ge molar fraction and the device’s physical behavior for all states are discussed. Second, many analog/radio frequency (RF) figures of merit (FoMs) in terms of transconductance (g_m), gate-to-gate capacitance (C_GG), cutoff frequency (f_T), gain bandwidth product (GBP), transit time (τ), and transconductance frequency product (TFP) are investigated. The fit configuration SiGe-JLGAA device demonstrates g_m = 67.4 µS, f_T = 1033 GHz, GBP = 115 GHz, TFP = 4.2 THz/V and τ = 1.3 × 10¹³ s, whereas the corresponding values for a conventional device are 13.5 µS, 354 GHz, 37 GHz, 1.2 THz/V and 5.9 × 10¹³ s, respectively. In addition, the reliability of the proposed device in terms of linearity for the three forms is compared. Finally, using a Verilog-A model in Cadence tool, the applications of the SiGe-JLGAA device in designing two types of inverters, binary and ternary, are demonstrated. The fit form exhibits superior DC and transient characteristics compared to other structures. The proposed device significantly enhances all configurations compared to the conventional JLGAA structure, thereby opening up a wide range of applications in digital circuits.

Terahertz light sources with small size and high output enable a variety of new applications. Free-electron laser (FEL) is the most powerful light source in the terahertz (THz) range with perfect wavelength tunability. However, the size of the FEL facility is too large. We are developing a table-top THz FEL using a small microtron accelerator. Through the development of a high-performance and compact undulator and a new waveguide-mode resonator, we confirmed that an FEL size of 1.5 × 2 m² is possible. One of the reasons we could design the small FEL is because we do not use electromagnets to force the electron beam into and out of the FEL resonator. We have developed an out-coupling mirror of the FEL resonator for a wide spectral range from 0.5 to 1 THz to have a structure in which the electron and THz beam transmit simultaneously without any bending magnets. The out-coupling mirror has wire-grid-polarizer (WGP) structure in the center. This paper discusses optimizing the WGP's parameters like wire thickness and period to get appropriate reflectance and transmittance in the 0.5–1 THz region and has low electron beam loss in the waveguide-based resonator using the COMSOL Multiphysics simulation. Simulations found the optimized value of wire thickness and period as 20 and 100 µm, respectively. We further calculated the TE transmittance of the WGP, which is 1-030% for the optimized values, depending on the frequency, ranging from 0.5 to 1 THz. Experiments using the THz time-domain spectroscopy method validated that the measured results agreed with those of the simulations.

In targets like airplanes, rockets, or missiles, there are both the target and the plume. When tracking the target through imaging optics, the plume can become background depending on the perspective of the optical system. When plumes are in the background, the target image may be obscured by the saturation of the plume signals. In this study, a range-gated short-wave infrared (SWIR) imaging system was considered for the acquisition and tracking of the target against the plume background. The target signal is the illumination laser light reflected from the target and the background signal is the self-radiation of the plume. We considered a method using the illumination laser energy and the detector integration time to increase the target signal and decrease the plume signal. We analyzed the system signal-to-noise ratio (SNR) as a function of the illumination laser energy and the detector integration time. As a result, we derived system design specifications satisfying the SNR greater than 2.5.

We consider the holographic dark energy model with axial torsion which satisfies the cosmological principle. Subsequently, by using the torsional analogs of Friedmann equations for the new equation from Einstein–Cartan gravity theory, we obtain the equation of state for dark energy in this model. We find that the extended holographic dark energy from the particle horizon as the infrared (IR) cut-off does not give the accelerating expansion of the universe. Also, employing the future event horizon as IR cut-off still achieves the accelerating expansion of the universe. In contrast, there is a possibility that the Hubble radius as IR cut-off achieves the accelerating expansion of the universe in superluminal region for axial torsion. More precisely, the current value of ratio for torsion to the matter density, (gamma ^{0}=0.5) gives the equation of state of dark energy (omega _{Lambda }cong -1).

Quantum state tomography (QST) forms the foundational framework in quantum computing, enabling precise characterization of quantum states through specialized measurement arrays. This is crucial for assessing the fidelity and coherence of quantum states in various quantum systems. The complexity and high dimensionality of quantum states require advanced statistical methods to meet modern quantum paradigms’ precision and computational needs, as traditional methods often struggle with inefficiencies and inaccuracies. Conventional approaches in QST typically use linear inversion and maximum likelihood estimators, which often face computational redundancies and perform sub-optimally in high-dimensional quantum architectures. This exposition introduces pioneering statistical methodologies that combine Bayesian Inference, Variational Quantum Eigensolver, and Quantum Neural Networks to achieve enhanced fidelity approximation. The analytical discussion is supported by synthetic quantum states, demonstrating the efficacy and applicability of these statistical methods across various quantum matrices. Preliminary empirical results show a significant increase in fidelity and a notable reduction in error margins, highlighting the potential of these advanced statistical methodologies in optimizing quantum state reconstructions. Additionally, leveraging the inherent symmetry properties in quantum systems could further improve the efficiency and accuracy of state reconstructions, offering additional pathways for advancing the field.

Synaptic transistors are considered to hold great potential as electronic devices for constructing brain-inspired neuromorphic cognitive systems. Synaptic transistors made of degradable and environmentally friendly materials are a common concern among researchers today. Egg whites are rich in sources and contain abundant hydrophilic functional groups, including –NH and –OH groups, which can facilitate the movement of protons. In this paper, a synaptic transistor using egg white as the gate dielectric for biomimetic simulation and neuromorphic computing is prepared. The fabricated synaptic transistor successfully simulates typical biological synaptic behaviors, such as excitatory postsynaptic current and double-pulse facilitation, and effectively models the transition from short-term memory to long-term memory. Furthermore, based on the long-term memory and conductance linearity of egg-white gated synaptic transistors, it completes the neuromorphic computation for handwritten digit recognition in neural networks, indicating that egg-white gated synaptic transistors have great potential for application in “green” neural-form electronic devices.

We investigate an expansion of the Dine-Fischler-Srednicki-Zhitnitsky (DFSZ) model aiming at realizing spontaneous CP violation. By introducing singlet heavy Majorana neutrinos and an additional new singlet scalar, we formulate the Yukawa Lagrangian and scalar potential for the extended model, highlighting their pivotal role in inducing CP violation. This study reveals that CP can spontaneously be broken at the 1-loop level, facilitated by the generation of the quartic couplings in the scalar potential which are imperative for inducing spontaneous CP violation. We discuss the implications of the model on the new axion. By presenting the leptonic Yukawa Lagrangian and the structure of the Dirac neutrino mass matrix within the minimal seesaw framework, we study the interply between the CP-violating phase arising from the extended DFSZ model and the phases of the Pontecorvo–Maki–Nakagawa–Sakata (PMNS) mixing matrix. A brief numerical analysis is conducted to illustrate the compatibility of the extended DFSZ model with observed neutrino oscillation parameters, providing insights into the origin of leptonic CP violation.

Korea-4GSR, a new synchrotron radiation facility currently under construction in Ochang, Chungbuk, South Korea, introduces three types of in-vacuum undulators (IVUs) for its first phase hard X-ray beamlines: IVU20, IVU22, and IVU24. These IVU types share a common 3-m-long framework capable of adjusting the magnetic gap size between 5 and 18 mm, but they differ in the undulator period length (λ_u). This study characterizes their photon beams in terms of brightness, spectral coverage, source size, angular divergence, coherent fraction, coherent flux, and total and central cone radiation powers, using undulator calculations. The three IVU types are comparable in brightness. IVU20 is the most coherent, although lacking spectral continuity at around 7.5 keV. IVU22 and IVU24 ensure spectral continuity, but their coherent flux is moderately compromised. The performance of the undulators is assessed in comparison to the Pohang Light Source-II (PLS-II) undulator and the U21 undulator at Advanced Photon Source Upgrade (APS-U).

The expansion and decay of excited and compressed nuclear matter produced in heavy-ion collisions across a broad range of incident energies are largely dependent on collective flow. Hydrodynamic theories suggest that the fluid-like behavior of nuclear matter produces a substantial azimuthal correlation in the particle emission. The greatest opportunity to discover nuclear matter compressibility and, indirectly, the nuclear equation of state is through precise measurements of collective flow. The collective flow of projectile fragments (PFs) of charge (Zge 2) produced in (^{84})Kr in interacts with emulsion (composite target) and Ag(Br) target at 1 A GeV for (N_{text {PF}}ge 3) and (N_{alpha }ge 3) has been evaluated using azimuthal correlation functions. The collective flow is observed to be the most pronounced in semi-central collisions. The amplitude of the collective flow appears to be pretty stable at relativistic energy, according to our observation. Additionally, the obtained outcomes are compared to other existing experimental data.