Highlights
Abstract +
SPECIAL TOPIC—Non-equilibrium transport and active control strategy in low-temperature plasmas
EDITOR'S SUGGESTION
Diagnosing global properties of dusty plasma based on machine learning from single particle dynamics
2025, 74 (20): 205202.
doi: 10.7498/aps.74.20251129
Abstract +
Currently, it is a great challenge to accurately diagnose global properties of dusty plasmas from limited data. Based on machine learning, a novel diagnostic method for various global properties in dusty plasma experiments is developed from single particle dynamics. It is found that for both two-dimensional (2D) dusty plasma simulations and experiments, the global properties such as the screening parameters κ and the coupling parameter Γ can be accurately determined purely from the position fluctuations of individual particles. Hundreds of independent Langevin dynamical simulations are performed with various specified κ and Γ values, resulting in a great number of individual particle position fluctuation data, which can be used for training, validating, and testing various convolutional neural network (CNN) models. To confirm the feasibility of this diagnostic method, three different CNN models are designed to determin the κ value. For the simulation data, all these CNN models perform excellently in determining the κ value, with the averaged determined κ value almost equal to the specified κ value. For the experiment data, the distribution of the determined κ values always exhibits one prominent peak, which is very consistent with the κ value obtained from the widely accepted phonon spectra fitting method. Furthermore, this diagnostic method is extended to simulatneously determining both the κ and Γ values, achieving satisfactory results by using 2D dusty plasma data from both simulations and experiments. The excellent performance of the CNN models developed here clearly indicates that through machine learning, the global properties of 2D dusty plasmas can be fully characterized purely from single particle dynamics.
SPECIAL TOPIC—Non-equilibrium transport and active control strategy in low-temperature plasmas
EDITOR'S SUGGESTION
2025, 74 (20): 205204.
doi: 10.7498/aps.74.20251096
Abstract +
Low-pressure radio-frequency inductively coupled discharges can produce uniformly distributed monodisperse particles and plasma, making them widely used in nanodevice fabrication. The manufacturing of nanodevices typically requires the generation of particles ranging from nanometer to submicron scales. These particles usually carry negative charges and can significantly influence the discharge characteristics of the plasma. This study investigates the effects of particle size and density on electron bounce resonance heating (BRH) and fundamental plasma properties in low-pressure inductively coupled plasmas (ICPs) by using a hybrid model. The hybrid model consists of kinetic equation, electromagnetic field equation, and global model equation. The simulation results show that as the dust radius or density increases, the BRH effect characterized by the formation of a plateau in the probability function of electron energy, is gradually suppressed and eventually disappears, accompanied by a decrease in electron temperature, an increase in electron density, and an increase in particle surface potential. The dust charge decreases with the increase of particle density, while exhibiting a nonmonotonic variation with particle radius. The results show that the loss of high-energy electrons caused by the dust particles may create a more favorable plasma environment for the growth of monodisperse nanoparticles with low defects. Such an improvement in particle quality is crucial for reducing trap densities and enhancing the electrical performance of nanoparticle-based electronic devices.
EDITOR'S SUGGESTION
2025, 74 (20): 202101.
doi: 10.7498/aps.74.20250898
Abstract +
In this work, we investigate the properties of strange quark matter (SQM) and color-flavor-locked (CFL) quark matter under zero temperature or strong magnetic fields within MIT bag model. We find that the thermodynamical properties of CFL quark matter are strongly affected by pairing energy gap Δ and magnetic field. The sound velocity of CFL quark matter and the tidal deformability of CFL quark stars both increase with Δ increasing, while the central baryon density of the maximum star mass in CFL state decreases with Δ. Specifically, the equation of state (EOS) of the CFL quark matter becomes stiffer with the increase of Δ, and the pressure becomes anisotropic when considering the magnetic field in the CFL quark matter. Our results indicate that the mass-radius relations of the CFL quark matter within the MIT bag model can describe the recent observations of pulsars, and that the maximum mass of CFL quark star increases with the increase of Δ. Moreover, the research results indicate that the mass of CFL quark star depends on the magnetic field strength and its orientation distributions within the magnetars, and the polytropic index of CFL quark matter decreases with the increase of star mass.
EDITOR'S SUGGESTION
2025, 74 (20): 203101.
doi: 10.7498/aps.74.20250959
Abstract +
The challenge in transporting water molecules through one-dimensional, large, disjoint nanochannels arises from the breaking of the water bridge. Even under significant pressure differences, water molecules are difficult to transport through these large disjoint nanochannels. Restoring the broken water bridge is crucial for maintaining continuous water transport through disjoint nanochannels. Current repairing methods, including the application of uniform or terahertz electric fields, are passive solutions. Once the electric fields are removed, it will stop working, causing the bridge to break again. In this study, molecular dynamics simulations are employed to investigate water transport through disjoint nanochannels with large nanogaps mediated by the coverage of coaxial nanochannels. The results reveal that as the diameter of the covered nanochannel decreases, the peak interaction between water molecules and the nanochannel decreases, which facilitates the reformation of the water bridge within the nanogap region. The water transfer rate through the disjoint nanochannel exhibits a non-monotonic dependence on the covered nanochannel diameter: it increases rapidly initially, then decreases with further increase in diameter, eventually reaching a relatively stable flow rate. Increasing the diameter of the covered nanochannel enhances water occupancy within the disjoint nanochannel, while the velocity and order parameter of water molecules display an initial increase followed by a decrease with further increase in diameter. These results offer significant insights into understanding the influence of covered nanochannels on water transport through disjoint nanochannels andproviding novel approaches for repairing broken water bridges in disjoint nanochannel systems.
Abstract +
The multilayer structure of extreme ultraviolet (EUV) masks limits the penetration depth of traditional inspection techniques at non-working wavelengths, thus hindering the effective examination of buried phase defects. Developing defect characterization techniques operating at the 13.5 nm wavelength is crucial for overcoming the quality bottleneck in EUV mask fabrication. Synchrotron radiation light source, with their stable EUV wavelength, cleanliness, and high power density, represents an ideal light source for EUV mask defect characterization research. In this work the current state of technology development for mask characterization at the world's four major synchrotron radiation facilities are systematically reviewed. Through comparative analysis, their working principles, technical advantages, and limitations are investigated in depth, and provide a forward-looking discussion on future trends. In response to the specific requirements for EUV mask defect detection and review, this paper discusses the requirements for the next-generation system platform, which integrates deep detection and review functions, develops novel compact light sources, and innovatively combines the advantages of various imaging techniques to improve the numerical aperture (NA) of imaging systems. This aims to achieve a theoretical resolution of over 20 nm, meeting the future demands of the EUV lithography industry for higher NA (>0.55) and shorter wavelengths (6.7 nm). Regarding the prospects of extending synchrotron radiation to industrial applications, a compact synchrotron radiation source, which can be developed on-site in semiconductor facilities, is introduced to accelerate the research and development cycle, while achieving the synergistic integration of imaging technologies. This paper focuses on the application of phase recovery principle of ptychography to Fourier synthesis illumination (FSI), achieving aberration correction in lens-based systems through synthetic aperture extension. In this paper, the working principles, performance benchmarks, technical challenges, and emerging development trends of existing synchrotron radiation-based EUV mask characterization techniques are investigated. It provides an important reference for designing next-generation EUV mask characterization system platforms.
INSTRMENTATION AND MEASURMENT
EDITOR'S SUGGESTION
2025, 74 (20): 200401.
doi: 10.7498/aps.74.20250852
Abstract +
Gravitational wave astronomy has rapidly developed into a powerful means of probing compact objects and understanding the evolution of the Universe. In order to improve sensitivity and expand the detection band, ground-based laser interferometers such as LIGO, Virgo, and KAGRA are constantly upgraded. This review summarizes their systematic development with an emphasis on noise sources and mitigation strategies. After outlining the principle of gravitational wave detection with laser interferometry, we analyze dominant noise sources, including quantum vacuum fluctuations, thermal noise, and seismic disturbances, and introduce techniques such as frequency-dependent squeezed light, advanced seismic isolation, multi-stage suspensions, and cryogenic mirrors. For LIGO, we highlight the transition from the Initial to Advanced configurations, which results in strain sensitivities of the order of $10^{-24}/\sqrt{\text{Hz}}$ and leads directly to the first detection, GW150914, and over one hundred subsequent events during O1 to O4. The unique superattenuator system of Virgo and its recent implementation of squeezed light, as well as the underground design of KAGRA and the use of cryogenic sapphire test masses, represent different approaches to suppressing low-frequency and thermal noise. In addition, we compare the technical routes adopted by different detectors and summarize the lessons learned from their upgrades, thereby providing valuable guidance for designing future detectors. Finally, we present next-generation projects, including LIGO Voyager, the Cosmic Explorer, and the Einstein Telescope, which aim to increase sensitivity by up to orders of magnitude and provide new research opportunities for developing gravitational-wave cosmology and fundamental physics. Overall, the development of detector technologies has been a key driving force for advances in gravitational wave astronomy, and the forthcoming facilities will change our ability to explore the universe.
SPECIAL TOPIC—High-pressure modulation and in situ characterization of optoelectronic properties
EDITOR'S SUGGESTION
2025, 74 (20): 206201.
doi: 10.7498/aps.74.20250912
Abstract +
SPECIAL TOPIC—High-pressure modulation and in situ characterization of optoelectronic properties
EDITOR'S SUGGESTION
2025, 74 (20): 200701.
doi: 10.7498/aps.74.20251034
Abstract +
Two-dimensional (2D) materials, due to their outstanding photoelectric properties, have demonstrated significant potential in both fundamental scientific research and future technological applications, including optoelectronics, energy storage, and conversion devices, establishing them as a cutting-edge research field in condensed matter physics and materials science. The distinctive layered structure of 2D materials renders their physical properties highly sensitive to external stimuli. High-pressure technology, serving as an efficient, continuous, and clean tuning tool, enables precise structural control and optimization of the photoelectric properties of 2D materials by compressing atomic distances, strengthening interlayer coupling, and even inducing structural phase transitions. This article focuses on prototypical two-dimensional materials, including graphene, transition metal dichalcogenides (TMDs), and two-dimensional metal halide perovskites. Employing the diamond anvil cell combined with multimodal in situ high-pressure characterization techniques such as X-ray diffraction, Raman spectroscopy, photoluminescence, and electrical transport measurements, we systematically elucidate the effects of high pressure on the structural and photoelectric properties of these materials. The key findings indicate that high pressure can induce the graphene to transition from a semimetal state to a semiconducting state, even a superconducting state, triggering off structural phase transitions and semiconductor-to-metal transitions in TMDs such as MoS2 and WTe2, and leading to a pressure-dependent bandgap narrowing and significant enhancement of luminescence intensity in two-dimensional perovskites. This work highlights the utility of high-pressure techniques in revealing the intrinsic correlations between the microstructure and macroscopic properties of two-dimensional materials. Furthermore, it discusses the key challenges and opportunities in this emerging research area, providing insights into the development and practical application of novel functional materials.
EDITOR'S SUGGESTION
2025, 74 (20): 206801.
doi: 10.7498/aps.74.20251021
Abstract +
SnTe-type topological crystalline insulators (TCIs) possess multiple Dirac-like topological surface states under the mirror-symmetry protection. Superconducting SnTe-type TCIs are predicted to form multiple Majorana zero modes (MZMs) in a single magnetic vortex. For the spatially isolated MZMs, there is only one MZM in a single vortex at surface. However, experimental demonstration of coupling the two isolated MZMs by changing wire length or intervortex distance is very challenging. For the multiple MZMs, two or more MZMs can coexist together in a single vortex. Thus, the novel property is expected to significantly reduce the difficulty in producing hybridization between MZMs. Recently, the experimental evidence for multiple MZMs has been observed in a single vortex of the superconducting SnTe/Pb heterostructure. However, SnTe is a heavily p-type semiconductor which is very difficult to induce the p-type to n-type transition via doping or alloying. The study on the Fermi-level tuning of SnTe-type TCIs is important for detecting and manipulating multiple MZMs. In this work, we report the influence of defects, such as film edge, grain boundary and dislocation, on the electronic property of Sn1–xPbxTe/Pb. The Sn1–xPbxTe films are prepared on the Pb (111) films grown on the Si (111) substrate by the molecular beam epitaxial technology. The structural and electronic properties of the Sn1–xPbxTe films are detected in situ by using low-temperature scanning tunneling microscopy and spectroscopy. The differential conductance tunneling spectra show that the minima of dI/dV spectra taken in the areas near the film edge, the grain boundary and the dislocation of Sn1–xPbxTe grown on Pb can be significantly changed to the energy very close to the Fermi level or even about –0.2 eV below the Fermi level, whereas the minima of dI/dV spectra taken in the areas far away from the defects are always at about 0.2 eV above the Fermi level. It indicates that these quasi one-dimensional defects, rather than Pb alloying, play an important role in modifying electronic property of the Sn1–xPbxTe/Pb heterostructure. Moreover, the Pb alloying will suppress the formation of zero-energy peak in the vortex. These results are expected to develop the new methods that do not require doping or alloying for the Fermi-level tuning of the SnTe-type topological superconducting devices.
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