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Microscopic theory of spin relaxation anisotropy in graphene with proximity-induced spin-orbit coupling
摘要： We present a microscopic theory of spin dynamics in weakly disordered graphene with uniform proximity-induced spin-orbit coupling (SOC). A time-dependent perturbative treatment is employed to derive the spin Bloch equations governing the spin dynamics at high electronic density for arbitrary ratio λSOC/η, where η is the disorder-induced quasiparticle broadening and λSOC is the largest spin-orbit energy scale. Rich scenarios are predicted, depending on a delicate competition between interface-induced Bychkov-Rashba and spin-valley interaction. In the motional narrowing regime of weak SOC (λSOC (cid:2) η), the anisotropy ratio of out-of-plane to in-plane spin lifetimes ζ = τ ⊥ s agrees qualitatively with a toy model of spins in a fluctuating SOC field proposed recently by Cummings and co-workers Phys. Rev. Lett. 119, 206601 (2017). For well-resolved SOC (λSOC (cid:2) η), the spin dynamics is characterized by fast damped oscillations with spins relaxing on the timescale of a single scattering event. In this regime, qualitatively different formulas for ζ are obtained, which can be useful to model spin transport in ultraclean van der Waals heterostructures.
关键词： spin-orbit coupling,van der Waals heterostructures,spin dynamics,Bychkov-Rashba,graphene,spin-valley interaction
更新于2025-09-04 15:30:14
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[IEEE 2018 Global Smart Industry Conference (GloSIC) - Chelyabinsk, Russia (2018.11.13-2018.11.15)] 2018 Global Smart Industry Conference (GloSIC) - Numerical Simulation of the Transverse and Longitudinal Shifts of Reflected Beam
摘要： The effects of the spin-orbit interaction of light are observed at the wavelength scale and can be used in nanophotonics. The computer simulation of these effects is a necessary tool for creating devices, based on the spin-orbit interaction of light. We have developed a software package in Python to simulate two known effects, namely, transverse and longitudinal shifts of the center of gravity of beams at the total internal reflection. The package is based on the algorithm for the numerical solution of Maxwell's equations by the finite difference time domain method. We have used the modification of PML – UPML as absorbing boundary conditions. We simulated the refraction and total internal reflection of an electromagnetic wave at the plane interface between two transparent dielectrics and calculated the depth of penetration of a non-uniform electromagnetic wave, occurring at total internal reflection in the optically less dense medium. To test the software package, we have compared the reflection coefficients of the electromagnetic wave for the normal and oblique incidence on the plane interface, calculated by the simulation with the coefficients, obtained by Fresnel formulas for the s-polarization of the wave. We have numerically simulated the shifts of the center of gravity of beams of finite size in the plane of incidence and perpendicular to it, namely, the effects of Goos-H?nchen and Fedorov. The dependence of the direction of the transverse shift on the sign of the circular polarization of the incident beam was demonstrated. The dependence of the longitudinal shift on the direction of linear polarization is also demonstrated. It should be stressed that the developed software package can be applied for simulating of the longitudinal and transverse shifts in anisotropic media, media with optical activity, as well as thin films on the dielectric surface.
关键词： Goos-H?nchen effect,Fedorov-Imbert effect,spin-orbit interaction of light,FDTD,PML
更新于2025-09-04 15:30:14
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CVD Diamond Interaction with Fe at Elevated Temperatures
摘要： Chemical vapor deposition (CVD) diamond is a prospective thin film material for cutting tools applications due to the extreme combination of hardness, chemical inertness, and thermal conductivity. However, the CVD diamond cutting ability of ferrous materials is strongly limited due to its extreme affinity to iron, cobalt, or nickel. The diamond–iron interaction and the diffusion behavior in this system are not well studied and are believed to be similar to the graphite–iron mechanism. In this article, we focus on the medium-temperature working range of 400–800 ?C of a CVD diamond–Fe system and show that for these temperatures etching of diamond by Fe is not as strong as is generally accepted. The starting point of the diamond graphitization in contact with iron was found around 400 ?C. Our results show that CVD diamond is applicable for the cutting of ferrous materials under medium-temperature conditions.
关键词： Fe–C interaction,CVD diamond,diffusion
更新于2025-09-04 15:30:14
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Selective recognition of Cr (VI) ion as Cr <sub/>2</sub> O <sub/>7</sub><sup>2?</sup> in aqueous medium using CTAB‐capped anthracene‐based nanosensor: Application to real water sample analysis
摘要： Surfactant‐capped nanoparticles of 9, 10‐diphenyl anthracene prepared by reprecipitation method found highly fluorescent due to aggregation‐induced enhanced emission (AIEE). Cetyltrimethyl ammonium bromide (CTAB) surfactant not only generated positive zeta potential on the surface of nanoparticles to attract anions of interest but also stabilized nanoparticles into brick‐shape morphology. The fluorescence of nanoparticles is quenched by Cr2O7 ion very significantly in comparison with other diverse ions, namely, MnO4, S2O8 showed increase in the fluorescence of nanoparticles, the interference found is negligible in the Cr (VI) analysis. The selectivity and sensitivity of nanoparticles for recognition of Cr2O7 were explored by systematic fluorescence titration. The fluorescence quenching data fits into the usual Stern‐Volmer equation. A calibration curve constructed by plotting quenching of fluorescence (ΔF) against concentration of Cr (VI) exhibiting a linear fit in the equation, ΔF = 3070x, is used for the estimation of chromium concentration (x). The correlation coefficient value R2 = 0.998 obtained from curve is nearly equal to 1 indicates linear fit between quenching data and concentration of Cr (VI). The estimated values of limit of detection (LOD) in the method 0.01392 μg.mL?1 is far below the permissible value of Cr (VI) 0.05 μg.mL?1 in drinking water approved by world health organization (WHO) and United State Environmental Protection Agency (USEPA). The proposed method of Cr (VI) detection is applied for real sample collected from hard chrome deposition industry from nearby region. The amount of Cr (VI) estimated by present method is comparable with AAS determination for the same samples.
关键词： Diphenylanthracene nanoparticles,Cr (VI) ion,CTAB,aggregation induced enhanced emission,electrostatic interaction
更新于2025-09-04 15:30:14
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Variant Construction from Theoretical Foundation to Applications || Synchronous Property—Key Fact on Quantum Interferences
摘要： Double-slit experiment plays a key role in Quantum Theory to distinct particle and wave interactions according to Feynman’s claims. In this chapter, double path model and variant logic principle are applied to establish a simulation system for exhaustive testing targets. Using Einstein quanta interaction, different measure quaternion structures are investigated. Under Symmetry/Anti-symmetry and Synchronous/Asynchronous interaction conditions, eight groups of statistical results are generated as eight histograms to show their distributions. From this set of simulation results, it can be recognized that the synchronous condition is the key fact to generate quantum wave interference patterns and, in addition, the asynchronous condition is the key fact to make classic particle distributions. Sample results are illustrated and explanations are discussed.
关键词： Probability,Interaction,Double path,Simulation,Statistics
更新于2025-09-04 15:30:14
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Organic-Inorganic Hybrid Nanoflowers as Potent Materials for Biosensing and Biocatalytic Applications
摘要： Flower-shaped organic-inorganic hybrid nanostructures, termed nanoflowers, have received considerable recent attention as they possess greatly enhanced activity, stability, durability, and even selectivity of entrapped organic biomolecules, which are much better than those from the conventional methods. They can be synthesized simply via co-incubation of organic and inorganic components in aqueous buffer at room temperature and yield hierarchical nanostructures with large surface-to-volume ratios, allowing for low-cost production by easy scale-up, as well as the high loading capacity of biomolecules without severe mass transfer limitations. Since a pioneering study reported on hybrid nanoflowers prepared with protein and copper sulfate, many other organic and inorganic components, which endow nanoflowers with diverse functionalities, have been employed. Thanks to these features, they have been applied in a diverse range of areas, including biosensors and biocatalysis. To highlight the progress of research on organic-inorganic hybrid nanoflowers, this review discusses their synthetic methods and mechanisms, structural and biological characteristics, as well as recent representative applications. Current challenges and future directions toward the design and development of multi-functional nanoflowers for their widespread utilization in biotechnology are also discussed.
关键词： Organic-inorganic hybrid nanoflowers,Coordination interaction,Biosensor,Enzyme immobilization,Biocatalysis
更新于2025-09-04 15:30:14
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Amplification and Compression of Radiation Emitted by a Dense Relativistic Cold Electron Beam
摘要： Starting from a three-wave interaction system of equations for free-electron lasers in the framework of a quantum fluid model, the full spatio-temporal solution of this set of equations is numerically obtained. Although this quantum fluid model does not take into account the electron recoil, it is accurate enough to model free-electron lasers down to soft X-ray range using a counter propagating optical wiggler and a moderately relativistic electron beam for a table-top compact device. We have shown that the scattered radiation is amplified and divided into sub-pulses while it absorbs energy from the optical wiggler through the negative energy beam plasma mode. Furthermore, the leading pulse gets more energy than the others while the longitudinal waist is reduced and has a shape similar to a “π-pulse” solution from the sine-Gordon equation.
关键词： FEL instability,Three-wave interaction
更新于2025-09-04 15:30:14
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Synthesis, physicochemical and quantum chemical studies on a new organic NLO crystal: Cinnamoylproline
摘要： Cinnamoylproline was synthesized and the crystal was grown from solution by the slow evaporation method. The crystal belongs to the trigonal crystal system with non-centrosymmetric space group P31. The calculated geometry and experimental geometry from single crystal X-ray data were compared. Intermolecular interactions were studied using Hirshfeld surface analysis and its real space functions were calculated using Atoms In Molecules (AIM) and its isosurfaces were visualized using Non-covalent interaction analysis. Optical transparency of the crystal was analyzed by UV-Vis analysis and it was found that the crystal has good optical transparency in the visible range and the lower cut-off wavelength was found to be 326 nm. In the photoluminescence spectrum, a broad emission peak at 369 nm was observed. The functional groups were analyzed using FTIR techniques and the vibrational frequencies from experimental and theoretical values were compared. It was inferred from the TG-DTA studies that the crystal was thermally stable up to 375°C. Kurtz-Perry powder SHG analysis was also carried out with KDP as a reference. It showed that the crystal has 1.08 times greater efficiency than KDP. The first hyperpolarizability tensor of the molecule was calculated theoretically and theoretical second order susceptibility was obtained and compared with the experimental susceptibility.
关键词： Non Covalent Interaction (NCI),Crystal growth,Hirshfeld surface analysis,cinnamic acid,QTAIM,First hyperpolarizability
更新于2025-09-04 15:30:14
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Dual-ended readout small animal PET detector by using 0.5?mm pixelated LYSO crystal arrays and SiPMs
摘要： Small animal PET scanners need to have a high spatial resolution since the size of the organs of small animals is much smaller than that of humans, and also need to have a high sensitivity since the allowed injection dose is limited by the radiation dosimetry of the small organs. To simultaneously achieve high spatial resolution and high sensitivity for a small animal PET scanner, detectors with high position resolution, high efficiency and high depth of interaction (DOI) resolution are required. In this work, three 17 × 17 pixelated LYSO arrays with crystal size of ～ 0.5 mm and an outer dimension of 10 × 10 × 20 mm3 are fabricated. The first LYSO array uses 80 μm thick BaSO4 reflector. The second and the third LYSO arrays use 65 μm thick Toray reflectors. The outermost side of the third LYSO array is also wrapped with k9 glass of the same size as the crystals in the array in order to improve the light collection and flood histogram quality for the edge crystals. The LYSO arrays are read out with two Hamamatsu SiPM arrays from both ends. The SiPM array is 4 × 4, with 3 × 3 mm2 pixel size and 0.2 mm gap in between the SiPM pixels. The SiPM array is read out with a resistor network circuit to reduce the number of signals from 16 to 4. The performance of the detector in terms of flood histograms, energy resolution, DOI resolution and timing resolution was measured. All three detectors provide good flood histograms and all crystals in an array can be clearly resolved. The average DOI resolutions of individual crystals are 1.84, 1.98 and 1.93 mm for the three detectors for events with energy E > 350 keV. The BaSO4 array has higher light output and provides a better average crystal energy resolution of 21.0 %. The photopeak amplitude of the Toray arrays changes with depth, which results in worse energy resolutions of 24.4 % and 23.8 % for the two detectors respectively. The average timing resolutions of individual crystals are 1.23, 1.27 and 1.24 ns for the three detectors for events with E > 350 keV. All three detector modules achieved high position resolution (0.5 mm crystal size), high efficiency (20 mm crystal length) and high DOI resolution (<2.0 mm) and can be used to build a high sensitivity small animal PET scanner with spatial resolution approaching the physical limit.
关键词： Dual-ended readout,Small animal PET,Depth of interaction,High resolution,SiPM
更新于2025-09-04 15:30:14
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Near-infrared Zeeman spectroscopy for the spatially resolved measurement of helium emission spectra in Heliotron J
摘要： A passive spectroscopic method that can measure spatially resolved emission spectra only by observing from a single diagnostic port without assuming plasma symmetry was applied to the stellarator-heliotron device Heliotron J. The emission spectra from the inboard and outboard sides were separated using the difference in their Zeeman effects. On the basis of the fact that in a spectrum as a function of the wavelength, the magnitude of the wavelength splitting by the Zeeman effect relative to the Doppler broadening increases with the wavelength, the method was applied to a near-infrared helium emission line (He I 1s2s 3S?1s2p 3P, 1083 nm), and it was confirmed that the uncertainty in the separated spectra was reduced compared with that in the application to visible emission lines. From the emissivity of the separated spectra, the local recycling flux was evaluated using the inverse photon efficiency method.
关键词： Zeeman effect,plasma surface interaction,stellarator,recycling,plasma spectroscopy,tomography
更新于2025-09-04 15:30:14