Accepted
, , Received Date: 2025-07-11
Abstract +
Torsion information is important for rotating systems, industrial monitoring, transportation engineering, and medical equipment. Optical fiber torsion sensors have significant advantages, such as immune to electromagnetic interference, small size, and light weight. Sagnac loop interferometer (SI) torsion sensors have attracted much attention due to their compact structure, high sensitivity, excellent stability, and low cost. However, their nonlinear response limits the measurement range, while the wide full width at half maximum and low signal-to-noise ratio (SNR) reduce the resolution of torsion sensors. To solve these problems, a fiber ring laser torsion sensor (FRLTS) based on homemade polarization-maintaining photonic crystal fiber (PM-PCF) is proposed in this work. The torsion sensor introduces a PM-PCF based SI into the erbium-doped fiber ring cavity as a filter and torsion sensor device. The interference spectrum of SI is derived by the transmission matrix method and simulated, and then the sensing principle of the sensor is obtained. Subsequently, the experimental system is set up to study the lasing output characteristics and torsion response of the FRLTS. By taking advantage of the narrow linewidth and high signal-to-noise ratio (SNR) of fiber ring lasers, a high-resolution fiber torsion sensor is successfully obtained. The experimental results show that the maximum linear torsion measurement range of the sensor can be extended to 480° (from –260° to 220°), the maximum torsion sensitivity is 0.032 nm/(°), and the resolution is as high as 0.681°. Furthermore, in a temperature range from 20 ℃ to 95 ℃, the temperature-induced wavelength variation is only 4×10–3 nm/℃, corresponding to a torsion angle measurement error of 0.16(°)/℃. Compared with existing reports, its temperature stability is increased by 37.5 times, while the temperature-induced error in angle measurements is reduced by 9.375 times. The proposed FRLTS not only successfully achieves high-resolution and wide-range torsion sensing, but also effectively suppresses cross-sensitivity caused by temperature. Therefore, the torsion sensor has significant potential applications in fields such as aerospace and robotics where precise measurement of minute torsion angle is required in special environments.
, , Received Date: 2025-07-18
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The rich dynamical analysis and predefined-time synchronization of simple memristive chaotic systems are of great significance in fully understanding the mechanism of dynamics formation and expanding the potential applications of chaotic systems. A four-dimensional memristive chaotic system with only a single nonlinear term is proposed to reveal various dynamic behaviors under the change of parameters and initial conditions, and to realize effective synchronization control. Based on dissipativity analysis and Lyapunov exponent computation, and combined with bifurcation analysis and multi steady state exploration, it is shown that the system possesses an infinite number of unstable equilibrium points and exhibits homogeneous and heterogeneous multistability, including point attractors, periodic attractors, and chaotic attractors. Moreover, it is found that amplitude modulation of the output signals of the system can be precisely achieved by adjusting internal parameters of the memristor, thus providing a theoretical basis for achieving effective amplitude modulation of periodic and chaotic signals. A predefined-time sliding mode surface with linear and bidirectional power-law nonlinear decay terms is constructed to address synchronization. Sufficient conditions for predefined-time convergence of synchronization errors are derived using Lyapunov stability theory, and a double-stage sliding mode controller with an adjustable upper bound on synchronization time is designed. The resulting control law ensures an adjustable synchronization time bound and rapid error suppression under arbitrary disturbances. Numerical simulations further confirm the effectiveness and robustness of the proposed control scheme, indicating that even under external disturbances or significant variations in initial conditions, the error variables can still converge precisely within the predefined time.
, , Received Date: 2025-06-20
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, , Received Date: 2025-06-20
Abstract +
Under high temperature and pressure conditions, silicon-based devices experience leakage and deformation due to the self-heating effect, making them unable to operate stably for a long time. Silicon carbide (SiC), as a representative third-generation semiconductor material, is an ideal option for high-temperature, high-frequency, and high-power electronic devices. However, the high-temperature performance limitations of 4H-SiC devices stem from the stability of ohmic contact electrodes and metal interconnections. The output of the lead electrodes is unstable at present, and oxygen intrusion at high temperatures can easily cause output failures. Previous studies indicate that the SiC/Ti/TaSi2/Pt multilayer structure holds significant potential for ohmic contacts. Building upon this ohmic contact foundation, this study proposes a batch sputtering-annealing process to prepare high-temperature-resistant lead electrodes. This involves altering the sequence of annealing and sputtering: first sputtering Ti/TaSi2 onto the SiC substrate and annealing to form the ohmic contact, followed by depositing a Pt protective layer to construct a novel SiC/Ti/TaSi2/Pt electrode structure. Comparative analysis of the two experimental groups is conducted using SEM, AES, XRD, thin-film stress measurement, and semiconductor analyzers. The batch-sputtered and annealed electrode structure can enhance density and reduce residual stress, with an initial specific contact resistivity of 6.35 × 10–5 Ω·cm2. High-temperature aging tests at 600 °C demonstrates superior electrical stability for electrodes formed by sputtering Pt onto Ti/TaSi2 after ohmic contact formation. These electrodes maintain ohmic characteristics even after 20-hour air aging, whereas traditional co-sputtered ohmic contacts transition to Schottky contacts. Pt effectively suppresses atomic diffusion and oxidation reactions, resulting in a smooth electrode microstructure without curling. The batch sputtering-annealing process not only greatly enhances the overall performance of SiC ohmic contacts but also provides crucial guidance for realizing the structural design and performance improvement of ohmic contacts by using other metal combinations. This approach holds significant reference value for the high-temperature packaging of third-generation semiconductor power devices and the development of electronic systems operating in harsh environments.
, , Received Date: 2025-07-30
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 method of the Fermi-level tuning for the SnTe-type topological superconducting devices that do not require doping or alloying.
, , Received Date: 2025-06-27
Abstract +
To meet the application requirements for continuous variable thrust capability and high-resolution characteristics for ion thrusters in drag-free flight missions of gravity gradient measurement satellites and precise orbit maintenance missions of near-Earth high-resolution observation satellites, the technical research on a high-resolution wide-range variable thrust ion thruster and its application verification are conducted. Leveraging the weak coupling and relative independence between the two critical physical processes of plasma discharge and ion beam extraction in Kaufman-type ion thrusters, a wide-range variable thrust ion thruster technical scheme with a divergent magnetic field configuration is proposed. The key technical investigations include wide-range discharge stability in the discharge chamber, a concave spherical ion optical system configuration design balancing wide-temperature-range ignition and high-density extraction requirements, and hollow cathode current emission continuity design. The discharge chamber structure based on a divergent magnetic field configuration can rapidly adjust plasma density under varying discharge intensities through optimal coordination of anode gas supply, magnetic induction intensity, and anode current, while resolving critical technical challenges in low-power discharge stability and high-power operational reliability. Adopting a concave spherical ion optical system, the technical challenge in matching grid thermal deformation spacing with the reliable extraction of high-density ion beams is addressed. The concave spherical configuration can realize full-power ion beam extraction within approximately 10 s in low-temperature environments. Meanwhile, the hollow cathode based on a lanthanum hexaboride (LaB6) emitter, through redundant design of emitter thickness and adaptive design of the cathode orifice aspect ratio, not only extends the emitter evaporation loss lifespan but also achieves stable operation within an emission current range of 0.5–3.4 A. Based on this, the design optimization and ground-based performance evaluation of a 10-cm-aperture high-resolution wide-range continuously variable thrust ion thruster are completed (In fact, such an ion thruster already achieved on-orbit flight in 2023.). Satellite on-orbit test results indicate that the 10-cm-aperture thruster achieves thrust regulation of 1.39–20.05 mN within a power range of 98.3–585.3 W, with specific impulse maintained at 547–3056 s, consistent with ground test results. The thrust response rate reaches approximately 3 mN/s, and thrust resolution exceeds 15 μN, outperforming ground test metrics. Compared with traditional chemical propulsion systems used for satellite orbit control, this thruster improves orbit maintenance accuracy by two orders of magnitude, effectively ensuring the implementation of satellite’s on-orbit engineering missions.
Abstract +
Layered transition metal dichalcogenides (TMDs) have attracted extensive interest due to their remarkable electronic, optical, and mechanical properties. Among them, molybdenum disulfide (MoS2) exhibits two main stacking polytypes: the centrosymmetric 2H phase and the non-centrosymmetric 3R phase. The latter has recently drawn attention for its spontaneous polarization, piezoelectricity, band modulation, and possible topological features, but its lattice dynamics and phonon-related properties remain far less understood. To address this gap, we present a comprehensive study of the layer-dependent Raman phonon characteristics of 3R-phase MoS2 and systematically compare them with those of the 2H phase.
Experimentally, we employed confocal Raman spectroscopy and polarization-resolved second-harmonic generation (SHG) to probe vibrational modes and stacking-dependent nonlinear responses of samples ranging from monolayer to bulk. SHG measurements provided an unambiguous means of distinguishing the stacking orders: while the SHG signal vanishes in even-layer 2H samples due to inversion symmetry, it persists strongly in 3R samples of any thickness. Raman spectra in the low-frequency region revealed distinct shear and breathing modes whose evolution with layer number was analyzed using both the linear chain model (LCM) and the more refined force constant model (FCM). While the LCM qualitatively captures the layer-dependent shifts of interlayer vibrations, the FCM provides quantitative agreement with experiments by explicitly incorporating nearest- and next-nearest-neighbor interactions as well as surface corrections.
To further interpret the relative intensities of interlayer Raman modes, we introduced the bond polarization model (BPM), which links mode-dependent scattering strength to the symmetry and orientation of chemical bonds. Our BPM analysis revealed pronounced asymmetry in charge redistribution for 3R stacking, leading to weaker interlayer binding energy compared to 2H (0.111 eV vs. 0.113 eV), and consequently a lower sliding barrier, consistent with the observed propensity of 3R crystals for interlayer slip. In the high-frequency region, both stacking types show characteristic in-plane and out-of-plane modes; however, the peak separation in 3R-phase MoS2 demonstrates stronger sensitivity to the layer number, making it a more reliable spectroscopic fingerprint for thickness identification. Importantly, we found that surface effects play a critical role in reproducing experimental high-frequency shifts in 3R samples, reflecting their weaker interlayer coupling and enhanced surface contributions.
In summary, this work establishes a complete picture of the phonon behavior in 3R-phase MoS2, bridging experiment and theory. Our results demonstrate that Raman spectroscopy combined with SHG provides a powerful toolkit for identifying stacking order and thickness in layered MoS2. By benchmarking LCM, FCM, and BPM models, we clarify the roles of interlayer coupling, stacking symmetry, and surface effects in shaping vibrational properties. These insights not only advance the fundamental understanding of lattice dynamics in non-centrosymmetric TMD polytypes, but also lay the groundwork for exploiting 3R-phase MoS2 in next-generation optoelectronic, piezoelectric, and quantum devices.
Experimentally, we employed confocal Raman spectroscopy and polarization-resolved second-harmonic generation (SHG) to probe vibrational modes and stacking-dependent nonlinear responses of samples ranging from monolayer to bulk. SHG measurements provided an unambiguous means of distinguishing the stacking orders: while the SHG signal vanishes in even-layer 2H samples due to inversion symmetry, it persists strongly in 3R samples of any thickness. Raman spectra in the low-frequency region revealed distinct shear and breathing modes whose evolution with layer number was analyzed using both the linear chain model (LCM) and the more refined force constant model (FCM). While the LCM qualitatively captures the layer-dependent shifts of interlayer vibrations, the FCM provides quantitative agreement with experiments by explicitly incorporating nearest- and next-nearest-neighbor interactions as well as surface corrections.
To further interpret the relative intensities of interlayer Raman modes, we introduced the bond polarization model (BPM), which links mode-dependent scattering strength to the symmetry and orientation of chemical bonds. Our BPM analysis revealed pronounced asymmetry in charge redistribution for 3R stacking, leading to weaker interlayer binding energy compared to 2H (0.111 eV vs. 0.113 eV), and consequently a lower sliding barrier, consistent with the observed propensity of 3R crystals for interlayer slip. In the high-frequency region, both stacking types show characteristic in-plane and out-of-plane modes; however, the peak separation in 3R-phase MoS2 demonstrates stronger sensitivity to the layer number, making it a more reliable spectroscopic fingerprint for thickness identification. Importantly, we found that surface effects play a critical role in reproducing experimental high-frequency shifts in 3R samples, reflecting their weaker interlayer coupling and enhanced surface contributions.
In summary, this work establishes a complete picture of the phonon behavior in 3R-phase MoS2, bridging experiment and theory. Our results demonstrate that Raman spectroscopy combined with SHG provides a powerful toolkit for identifying stacking order and thickness in layered MoS2. By benchmarking LCM, FCM, and BPM models, we clarify the roles of interlayer coupling, stacking symmetry, and surface effects in shaping vibrational properties. These insights not only advance the fundamental understanding of lattice dynamics in non-centrosymmetric TMD polytypes, but also lay the groundwork for exploiting 3R-phase MoS2 in next-generation optoelectronic, piezoelectric, and quantum devices.
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Abstract +
The discovery of superconductivity in Ruddlesden-Popper (RP) phase layered nickelates under high pressure has opened a new avenue for exploring unconventional pairing mechanisms beyond cuprates and iron-based superconductors. In particular, La3Ni2O7 exhibits a superconducting transition temperature (Tc) as high as 80 K at ~15 GPa, making it the second class of oxides that achieve liquid-nitrogentemperature superconductivity. Subsequent experiments have extended superconductivity to related compounds such as La4Ni3O10 and La5Ni3O11, as well as epitaxially grown thin films at ambient pressure. These findings have motivated extensive theoretical efforts to elucidate the microscopic pairing mechanism.
This review summarizes recent progress from the perspective of weak-coupling theories, including random phase approximation (RPA), functional renormalization group (FRG), and fluctuation-exchange (FLEX) approaches. Density functional theory (DFT) calculations reveal that the low-energy degrees of freedom are dominated by Ni 3dz2 and 3dx2-y2> orbitals. In La3Ni2O7, pressure-induced metallization of the bonding 3dz2 band produces the γ pocket, enhancing spin fluctuations and stabilizing superconductivity. These fluctuations support superconductivity through interlayer 3dz2 pairing characterized by an s± gap. Hole doping or substitution may restore the γ pocket and enable bulk superconductivity at ambient pressure.
For La4Ni3O10, theoretical calculations indicate predominantly s± pairing from interlayer 3dz2 orbitals, with weaker strength than La3Ni2O7, explaining its lower Tc and showing little sensitivity to band structure. In La5Ni3O11, composed of alternating single-layer and bilayer units, superconductivity mainly arises from the bilayer subsystem, again dominated by 3dz2 orbitals. Interestingly, the interplay between inter-bilayer Josephson coupling and the suppression of density of states leads to a dome-shaped Tc-pressure phase diagram, distinct from the monotonic behavior of La3Ni2O7.
Epitaxial (La,Pr)3Ni2O7 thin films display superconductivity above 40 K at ambient pressure. Theory predicts doping-dependent pairing: s± symmetry is favored at low doping levels, while dxy pairing emerges at higher doping, in agreement with experimental indications of both nodeless and nodal gap behaviors.
Beyond superconductivity, experiments have revealed spin-density-wave (SDW) order in bulk La3Ni2O7 and La4Ni3O10 at ambient pressure. Weak-coupling calculations confirm that these SDWs are driven by Fermi surface nesting and that their suppression under pressure gives rise to strong spin fluctuations which act as the glue for Cooper pairing. This highlights the intimate connection between the density-wave parent states and high-pressure superconductivity in nickelates.
In summary, weak-coupling theories provide a unified framework for RP nickelates, highlighting the key role of 3dz2 orbitals, interlayer pairing, and spin fluctuations. They suggest that pressure, doping, substitution, and epitaxial strain can optimize superconductivity and potentially achieve high-Tc phases at ambient pressure. Key challenges remain in clarifying orbital competition, the SDW-superconductivity interplay, and strong-correlation effects, requiring close collaboration between advanced experiments and multi-orbital many-body theory.
This review summarizes recent progress from the perspective of weak-coupling theories, including random phase approximation (RPA), functional renormalization group (FRG), and fluctuation-exchange (FLEX) approaches. Density functional theory (DFT) calculations reveal that the low-energy degrees of freedom are dominated by Ni 3dz2 and 3dx2-y2> orbitals. In La3Ni2O7, pressure-induced metallization of the bonding 3dz2 band produces the γ pocket, enhancing spin fluctuations and stabilizing superconductivity. These fluctuations support superconductivity through interlayer 3dz2 pairing characterized by an s± gap. Hole doping or substitution may restore the γ pocket and enable bulk superconductivity at ambient pressure.
For La4Ni3O10, theoretical calculations indicate predominantly s± pairing from interlayer 3dz2 orbitals, with weaker strength than La3Ni2O7, explaining its lower Tc and showing little sensitivity to band structure. In La5Ni3O11, composed of alternating single-layer and bilayer units, superconductivity mainly arises from the bilayer subsystem, again dominated by 3dz2 orbitals. Interestingly, the interplay between inter-bilayer Josephson coupling and the suppression of density of states leads to a dome-shaped Tc-pressure phase diagram, distinct from the monotonic behavior of La3Ni2O7.
Epitaxial (La,Pr)3Ni2O7 thin films display superconductivity above 40 K at ambient pressure. Theory predicts doping-dependent pairing: s± symmetry is favored at low doping levels, while dxy pairing emerges at higher doping, in agreement with experimental indications of both nodeless and nodal gap behaviors.
Beyond superconductivity, experiments have revealed spin-density-wave (SDW) order in bulk La3Ni2O7 and La4Ni3O10 at ambient pressure. Weak-coupling calculations confirm that these SDWs are driven by Fermi surface nesting and that their suppression under pressure gives rise to strong spin fluctuations which act as the glue for Cooper pairing. This highlights the intimate connection between the density-wave parent states and high-pressure superconductivity in nickelates.
In summary, weak-coupling theories provide a unified framework for RP nickelates, highlighting the key role of 3dz2 orbitals, interlayer pairing, and spin fluctuations. They suggest that pressure, doping, substitution, and epitaxial strain can optimize superconductivity and potentially achieve high-Tc phases at ambient pressure. Key challenges remain in clarifying orbital competition, the SDW-superconductivity interplay, and strong-correlation effects, requiring close collaboration between advanced experiments and multi-orbital many-body theory.
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Abstract +
This work investigates nonequilibrium phase transitions in a Rydberg atomic system with collective dissipation. [15,16] By combining mean-field theory [26] and Liouvillian spectral analysis [23-27,29,30], we reveal novel nonequilibrium phases induced by collective dissipation and compare the results from both approaches. Our findings demonstrate that collective dissipation not only generates interatomic correlations but also sustains persistent periodic oscillations [18,32] and a distinctive form of bistability, where the system may either evolve to a stationary state or sustain self-consistent oscillatory dynamics. This study highlights the rich nonequilibrium phenomena present in quantum many-body systems and provides an extensible spectral framework for exploring dissipative phases in Rydberg and related systems.
Recent experiments [10-13] have reported persistent oscillations in thermal Rydberg atomic ensembles, yet a theoretical consensus on their origin remains elusive. Motivated by these observations, we introduce a collective dissipation mechanism and employ both mean-field approximations and the Liouvillian spectrum method to systematically explore nonequilibrium phase transitions. Our results show that collective dissipation effectively induces interatomic correlations and sustains persistent periodic oscillations, whereas under the same parameters, independent dissipation leads the system to relax to a stationary state. Furthermore, the nonlinear effects arising from collective dissipation give rise to a novel type of bistability, in which the system can either converge to a fixed point or maintain self-consistent periodic oscillations. This mechanism is distinctly different from conventional bistability induced by Rydberg interactions, which involves two stationary states. Moreover, the Liouvillian spectral method, based on the quantum master equation, successfully captures features of nonequilibrium phase transitions even in finite-dimensional systems, and the results agree well with those obtained from mean-field approximation in the thermodynamic limit.
Our work not only provides a theoretical explanation for recently observed oscillatory phenomena but also predicts novel bistable states and rich nonequilibrium phase structures. It further verifies the effectiveness of the Liouvillian spectral approach in studying quantum many-body systems, contributing significantly to the understanding of microscopic mechanisms underlying nonequilibrium phase transitions.
Recent experiments [10-13] have reported persistent oscillations in thermal Rydberg atomic ensembles, yet a theoretical consensus on their origin remains elusive. Motivated by these observations, we introduce a collective dissipation mechanism and employ both mean-field approximations and the Liouvillian spectrum method to systematically explore nonequilibrium phase transitions. Our results show that collective dissipation effectively induces interatomic correlations and sustains persistent periodic oscillations, whereas under the same parameters, independent dissipation leads the system to relax to a stationary state. Furthermore, the nonlinear effects arising from collective dissipation give rise to a novel type of bistability, in which the system can either converge to a fixed point or maintain self-consistent periodic oscillations. This mechanism is distinctly different from conventional bistability induced by Rydberg interactions, which involves two stationary states. Moreover, the Liouvillian spectral method, based on the quantum master equation, successfully captures features of nonequilibrium phase transitions even in finite-dimensional systems, and the results agree well with those obtained from mean-field approximation in the thermodynamic limit.
Our work not only provides a theoretical explanation for recently observed oscillatory phenomena but also predicts novel bistable states and rich nonequilibrium phase structures. It further verifies the effectiveness of the Liouvillian spectral approach in studying quantum many-body systems, contributing significantly to the understanding of microscopic mechanisms underlying nonequilibrium phase transitions.
Abstract +
Brillouin Light Scattering (BLS) spectroscopy has emerged as a cornerstone technique for investigating elementary excitations in condensed matter systems, offering unique capabilities for non invasive characterization of magnon and phonon dynamics. This review examines the fundamental principles, technological evolution, and diverse applications of BLS across multiple research domains.
BLS operates through inelastic scattering between photons and quasiparticles (magnons, phonons), enabling precise measurement of excitation frequencies, propagation characteristics, and interaction mechanisms via detection of characteristic frequency shifts. Since Brillouin’s 1914 theoretical prediction and Gross’s 1930 experimental verification, the technique has evolved dramatically. The revolutionary development of tandem Fabry-Pérot interferometers by Sandercock in the 1970s established the foundation for modern high-resolution BLS systems, achieving contrast ratios exceeding 1010 and frequency resolution in the MHz range.
We detail four advanced BLS configurations: 1) Conventional wave-vector-resolved systems enabling precise dispersion relation measurements and detection of non-reciprocal spin wave propagation induced by Dzyaloshinskii-Moriya interactions; 2) Micro-focused BLS (μBLS) achieving sub-micrometer spatial resolution for nanoscale magnetic structure characterization; 3) Time-resolved BLS (TR-BLS) providing nanosecond temporal resolution for studying ultrafast dynamics, magnon Bose-Einstein condensation, and nonlinear phenomena; 4) Phase-resolved BLS (PR-BLS) enabling direct wave vector and phase measurements through electro-optical modulation.
Beyond traditional magnonic applications, BLS demonstrates remarkable versatility in phonon research and magnetoacoustic coupling studies. The technique’s polarization-sensitive detection allows simultaneous investigation of magnon-phonon hybrid states and energy transfer mechanisms. Importantly, BLS has successfully expanded into biomedical applications, providing non-contact characterization of cellular and tissue viscoelastic properties at GHz frequencies, revealing disease-related biomechanical changes.
As BLS technology continues advancing through improved instrumentation and novel methodologies, it serves as an indispensable platform spanning quantum materials research, magnonic device development, and cellular mechanobiology, positioning itself at the forefront of interdisciplinary science bridging condensed matter physics, materials engineering, and biomedical research.
BLS operates through inelastic scattering between photons and quasiparticles (magnons, phonons), enabling precise measurement of excitation frequencies, propagation characteristics, and interaction mechanisms via detection of characteristic frequency shifts. Since Brillouin’s 1914 theoretical prediction and Gross’s 1930 experimental verification, the technique has evolved dramatically. The revolutionary development of tandem Fabry-Pérot interferometers by Sandercock in the 1970s established the foundation for modern high-resolution BLS systems, achieving contrast ratios exceeding 1010 and frequency resolution in the MHz range.
We detail four advanced BLS configurations: 1) Conventional wave-vector-resolved systems enabling precise dispersion relation measurements and detection of non-reciprocal spin wave propagation induced by Dzyaloshinskii-Moriya interactions; 2) Micro-focused BLS (μBLS) achieving sub-micrometer spatial resolution for nanoscale magnetic structure characterization; 3) Time-resolved BLS (TR-BLS) providing nanosecond temporal resolution for studying ultrafast dynamics, magnon Bose-Einstein condensation, and nonlinear phenomena; 4) Phase-resolved BLS (PR-BLS) enabling direct wave vector and phase measurements through electro-optical modulation.
Beyond traditional magnonic applications, BLS demonstrates remarkable versatility in phonon research and magnetoacoustic coupling studies. The technique’s polarization-sensitive detection allows simultaneous investigation of magnon-phonon hybrid states and energy transfer mechanisms. Importantly, BLS has successfully expanded into biomedical applications, providing non-contact characterization of cellular and tissue viscoelastic properties at GHz frequencies, revealing disease-related biomechanical changes.
As BLS technology continues advancing through improved instrumentation and novel methodologies, it serves as an indispensable platform spanning quantum materials research, magnonic device development, and cellular mechanobiology, positioning itself at the forefront of interdisciplinary science bridging condensed matter physics, materials engineering, and biomedical research.
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Abstract +
Capacitively coupled plasma sources, which are widely used in the etching and deposition processes of semiconductor manufacturing, have the advantages of simple structure, low cost, and the ability to generate large-area uniform plasma. To meet the requirements of advanced processes, fluid models are usually required to simulate plasma sources and optimize their important plasma parameters, such as density and uniformity. In this paper, an independently-developed capacitive coupled plasma fast simulation program is employed to conduct three-dimensional fluid simulations of a dual-frequency capacitive coupled Ar/CF4 plasma source, with the aims of verifying the effectiveness of the program and investigating the influence of discharge parameters such as gas pressure, high and low-frequency voltages, low-frequency frequency, and background component ratios. The simulation results show that the program has an extremely high simulation speed. As the low-frequency voltage increases, plasma density initially remains approximately constant and then significantly increases, while plasma uniformity initially rises and then significantly decreases, the γ-mode heating of low-frequency source increases in this process, and becomes the dominant mode in replace of the α -mode of high-frequency source. As the lower frequency increases, plasma density initially remains approximately constant and then slightly increases, while plasma uniformity changes little, these are because the γ -mode heating is frequency independent, while the α -mode heating is much lower than that of high-frequency source. As the high-frequency voltage increases, plasma density significantly increases, while plasma uniformity initially rises and then significantly decreases, the α -mode heating of highfrequency source is significantly enhanced in this process. As the pressure increases, plasma density significantly increases, and plasma uniformity also rises significantly, the reason is the more complete collision between particles and background gases. As the Ar ratio in background gases increases, plasma density changes slightly, the densities of Ar-related particles generally increase and the densities of CF4-related particles generally decrease, although there are some non-monotonic changes in particle densities, which reflects the mutual promotion between some ionization and dissociation reactions.
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Abstract +
Polarization detection is a fundamental route to access the vectorial nature of light, underpinning advanced technologies in optical communication, intelligent sensing, and biosensing..Two-dimensional van der Waals materials, owing to their intrinsic anisotropy and tunable electronic properties, have emerged as a promising platform for high-performance polarization-sensitive photodetectors. Nevertheless, their intrinsically weak light absorption and limited photoresponse efficiency remain major bottlenecks. Plasmonic nanostructures, which enable strong localized field confinement and manipulation at the nanoscale, provide an effective strategy to overcome these limitations and substantially boost device performance. In this review, we systematically summarize the coupling mechanisms between plasmonic architectures and vdW materials, highlighting near-field enhancement, plasmon-induced hot-carrier generation, and mode-selective polarization coupling as key physical processes that enhance photocarrier generation and polarization extinction. Representative device implementations, including metallic gratings, hybrid nanoantennas, and chiral metasurfaces, are compared in terms of responsivity, detection speed, operating bandwidth, and polarization extinction ratio, revealing consistent improvements of one to two orders of magnitude over bare vdW devices. We further survey emerging applications in high-speed polarization-encoded optical communication, on-chip optical computing and information processing, and bioinspired vision and image recognition systems, where plasmonic-vdW hybrid detectors demonstrate unique advantages in miniaturization and energy efficiency. Finally, we discuss current challenges such as large-scale fabrication of uniform plasmonic arrays, spectral bandwidth broadening, and seamless integration with complementary photonic circuits, and outline future opportunities for next-generation polarization-resolved optoelectronic platforms.
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Abstract +
With the advantages of high energy density and high safety factor, solidstate batteries have gradually become the focus of people's attention and research in recent years. Lithium dendrites are a key factor affecting battery safety and service life, and in severe cases, battery short circuits can occur. Compared with liquid batteries, solid-state batteries rely on solid-state electrolytes with higher mechanical strength, which can effectively inhibit the growth of lithium dendrites, but with the increase of the number of charge-discharge cycles, the dead lithium produced by the incomplete dissolution of lithium dendrites gradually accumulates, and the performance of the battery gradually decreases. In this paper, the problem of dead lithium in solid-state batteries is studied by using COMSOL Multiphysics 6.2 finite element simulation software. Since the current research on dead lithium focuses on phase field models coupled with binary physics, there are few studies on the influence of electrochemical parameters on dead lithium. Therefore, the phase field method is used to simulate the dissolution of lithium dendrites and the formation of dead lithium under the coupling of force-thermal-electrochemical fields. When the heat transfer model is coupled, due to the change of lithium dendrite stress distribution, the difference in the morphology of dead lithium before and after the coupled heat transfer model is further studied by applying external pressure to change the stress. When the coupled mechanical field changes, the morphology of dead lithium before and after the coupled mechanical field is further studied by changing the temperature magnitude. At the same time, the effects of changes in three electrochemical parameters, namely diffusion coefficient, interfacial mobility and anisotropic strength, on the area of dead lithium were also explored. The conclusion shows that when the heat transfer model or mechanical field is coupled into the phase field model, the dendrite dissolution cut-off time and dead lithium area will change. When the base rises at high temperature or when low external pressure or high external pressure is applied, the area of dead lithium decreases. For changing the electrochemical parameters, reducing the diffusion coefficient, increasing the interfacial mobility and reducing the anisotropic strength can effectively reduce the area of dead lithium.
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Abstract +
Multiphoton microscopy (MPM) has become an essential research tool in biomedicine. Current MPM systems predominantly rely on Ti:sapphire lasers providing tunable femtosecond pulses at 720-950 nm. To access the second biological transparency window (1000-1350 nm), complex optical parametric oscillators are typically required. Furthermore, sources operating in the third biological transparency window (1600-1750 nm) are attracting significant attention for enhanced imaging depth. However, no ultrafast laser source simultaneously covering all three transparency windows exists, hindering the widespread application of MPM in life sciences. Here, we demonstrate a fiber-laser-based ultrafast source generating four-color tunable pulses across 800-1650 nm, covering the full spectral range for multiphoton excitation. This source leverages our proposed spectral selection technique via self-phase modulation (SESS). SESS ensures SPM-dominated spectral broadening, producing isolated spectral lobes. Filtering the outermost lobes generates near-transform-limited pulses with broad wavelength tunability. Using this supercontinuum excitation source, we successfully achieved label-free imaging of diverse biomedical specimens, validating the performance of MPM empowered by this novel driving source.
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Abstract +
The discovery of ambient-pressure nickelate high-temperature superconductivity provides a new platform for probing the underlying superconducting mechanisms. However, the thermodynamic metastability of Ruddlesden-Popper nickelates Lnn+1NinO3n+1 (Ln = lanthanide) presents significant challenges in achieving precise control over their structure and oxygen stoichiometry. This study establishes a systematic approach for growing phase-pure, high-quality Ln3Ni2O7 thin films on LaAlO3 and SrLaAlO4 substrates using gigantic-oxidative atomic-layerby-layer epitaxy. The films grown under an ultrastrong oxidizing ozone atmosphere are superconducting without further post annealing. Specifically, the optimal Ln3Ni2O7/SrLaAlO4 superconducting film exhibitsan onset transition temperature (Tc,onset) of 50 K. Four critical factors governing the crystalline quality and superconducting properties of Ln3Ni2O7 films are identified: 1) precise cation stoichiometric control suppresses secondary phase formation. In a Ni-rich sample (+7%), the thin film forms a Ln4Ni3O10 secondary phase, and the R-T curve correspondingly exhibits metallic behavior. In contrast, a Ni-deficient sample forms a Ln2NiO4 secondary phase, with its R-T curve indicating insulating behavior over the entire temperature range. 2) Complete atomic layer-by-layer coverage minimizes stacking faults. Deviation from ideal monolayer coverage induces in-plane atomic number mismatch, whichdirectly triggers out-of-plane lattice collapse or uplift near bulkequilibrium positions. 3) Optimized interface reconstruction can improve the atomic arrangement at the interface. This can be achieved through methods such as annealing the SrLaAlO4 substrate or pre-depositing a 0.5-unit-cell-thick Ln2NiO4-phase buffer layer, which enhances the energy difference between the Ln-site and Ni-site layers to promote proper stacking. 4) Accurate oxygen content regulation is essential for achieving a single superconducting transition and high Tc,onset. Although the under-oxidized sample demonstrates a relatively high Tc,onset (50 K), it displays a two-step superconducting transition. Conversely, the over-oxidized sample exhibits a reduced Tc,onset of 37 K and similarly manifests a two-step transition. These findings provide valuable insights for the layer-by-layer epitaxy growth of diverse oxide high-temperature superconducting films
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