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Spatial Characteristics of Thomson Scattering Spectra in Laser and Magnetic Fields
摘要： Spatial characteristics of Thomson scattering spectra are studied for an electron moving in the circularly polarized laser field in the presence of a strong uniform magnetic field. The results show that the angular distributions of the spectra with respect to the azimuthal and polar angles exhibit different symmetries, respectively, which depend on the fields and electron parameters sensitively and significantly. Moreover, for relatively large parameters such as high laser intensity, high magnetic resonance parameter as well as large initial momentum of electron, the two lobes in spectra tend to the laser-propagating direction so that the radiation can be collimated in the forward direction. Furthermore, an important finding is that by choosing the appropriate fields and initial momentum of electron, the high frequency part of the Thomson scattering spectra can reach the frequency range of soft x-ray, in which a high radiation power per solid angle as ～1011 a.u. can be obtained.
关键词： Thomson scattering,magnetic field,spatial characteristics,laser field,soft x-ray
更新于2025-09-12 10:27:22
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Phonon laser in a cavity magnomechanical system
摘要： Using phonons to simulate an optical two-level laser action has been the focus of research. We theoretically study phonon laser in a cavity magnomechanical system, which consist of a microwave cavity, a sphere of magnetic material and a uniform external bias magnetic field. This system can realize the phonon-magnon coupling and the cavity photon-magnon coupling via magnetostrictive interaction and magnetic dipole interaction respectively, the magnons are driven directly by a strong microwave field simultaneously. Frist, the intensity of driving magnetic field which can reach the threshold condition of phonon laser is given. then, we demonstrate that the adjustable external magnetic field can be used as a good control method to the phonon laser. Compared with phonon laser in optomechanical systems, our scheme brings a new degree of freedom of manipulation. finally, with the experimentally feasible parameters, threshold power in our scheme is close to the case of optomechanical systems. Our study may inspire the field of magnetically controlled phonon lasers.
关键词： cavity magnomechanical system,phonon laser,magnetic field control,magnon-phonon coupling
更新于2025-09-12 10:27:22
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Numerical simulations to study turbulent magnetic field amplification by nonlinear interaction of high-power laser and kinetic Alfvén waves in laboratory and astrophysical plasmas
摘要： The model contouring the dynamics of transient nonlinear interaction between the high-frequency extraordinary-elliptically polarized laser (HFXPL) and low-frequency kinetic Alfvén wave (LFKAW) dynamics in the magnetized plasma is the focal point of the present investigation. The quasistatic ponderomotive force driven by the HFXPL pump induces density cavitation and humps in the low-frequency kinetic Alfvén wave. In order to study the intricate localized structures of HFXPL pump waves that evolve with time, the requisite dimensionless equations of the coupled system (HFXPL and LFKAW) are evaluated by using numerical methods in the nonlinear stage. The typical scale sizes of these structures in the early phase are ≈9 μm, and the typical time to grow is ≈10 ps. The ensemble-averaged magnetic power spectra are also presented, indicating energy cascade. The rendered investigations follow direct relevance to the experimental observations and are imperative in understanding turbulence in astrophysical scenarios.
关键词： kinetic Alfvén waves,high-power laser,astrophysical plasmas,laboratory plasmas,nonlinear interaction,turbulent magnetic field amplification
更新于2025-09-12 10:27:22
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Magnetic-induced graphene quantum dots for imaging-guided photothermal therapy in the second near-infrared window
摘要： Graphene quantum dots (GQDs) are considered emerging nanomaterials for photothermal therapy (PTT) of cancer due to their good biocompatibility and rapid excretion. However, the optical absorbance of GQDs in shorter wavelengths (<1000 nm) limits their overall therapeutic efficacies as photothermal agent in the second near infrared window (1000-1700 nm, NIR-II). Herein, we report a type of GQDs with strong absorption (1070 nm) in NIR-II region that was synthesized via a one-step solvothermal treatment using phenol as single precursor by tuning the decomposition of hydrogen peroxide under a high magnetic field with an intensity of 9T. The obtained 9T-GQDs demonstrate uniform size distribution (3.6 nm), and tunable fluorescence (quantum yield, 16.67 %) and high photothermal conversion efficacy (33.45%). In vitro and in vivo results indicate that 9T-GQDs could efficiently ablate tumor cells and inhibit the tumor growth under NIR-II irradiation. Moreover, the 9T-GQDs exhibited enhanced NIR imaging of tumor in living mice, suggesting the great probability of using 9T-GQDs for in vivo NIR imaging-guided PTT in the NIR-II window.
关键词： magnetic field,NIR-II absorbance,photothermal conversion,cancer therapy,graphene quantum dot
更新于2025-09-12 10:27:22
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Confined electron states in two-dimensional HgTe in magnetic field: Quantum dot versus quantum ring behavior
摘要： We investigate the electron states and optical absorption in square- and hexagonal-shaped two-dimensional (2D) HgTe quantum dots and quantum rings in the presence of a perpendicular magnetic field. The electronic structure is modeled by means of the sp3d 5s? tight-binding method within the nearest-neighbor approximation. Both bulklike and edge states appear in the energy spectrum. The bulklike states in quantum rings exhibit Aharonov-Bohm oscillations in magnetic field, whereas no such oscillations are found in quantum dots, which is ascribed to the different topology of the two systems. When magnetic field varies, all the edge states in square quantum dots appear as quasibands composed of almost fully flat levels, whereas some edge states in quantum rings are found to oscillate with magnetic field. However, the edge states in hexagonal quantum dots are localized like in rings. The absorption spectra of all the structures consist of numerous absorption lines, which substantially overlap even for small line broadening. The absorption lines in the infrared are found to originate from transitions between edge states. It is shown that the magnetic field can be used to efficiently tune the optical absorption of HgTe 2D quantum dot and quantum ring systems.
关键词： HgTe,quantum dots,quantum rings,optical absorption,electron states,tight-binding method,magnetic field,Aharonov-Bohm oscillations
更新于2025-09-12 10:27:22
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Study of the static characteristic I-V and the electrical parameters corresponding to the shunt resistance Rsh and series resistance Rs per unit area of a solar cell with grain size
摘要： This paper presents a new technique based on the junction recombination velocity (Sf: junction recombination velocity) at the grain size for the evaluation of the series and shunt resistances. The study of the response of the solar cell and the parameters of recombination in grain size, which are the object of the investigation, is related to the study of the static characteristic I-V and electrical parameters Rs and Rsh under a magnetic field. This study has allowed us to address some of the theoretical aspects of the field solar cell in order to draw a conclusion and some perspectives. Based on the results obtained for the photocurrent density and the photovoltage, we will study the I-V characteristic of the solar cell to then be able to propose a model for the determination of the shunt resistance Rsh and the series resistance Rs. Series resistance investigations, including numerical simulations and field data tests, are conducted to examine the energetic behavior of the PV modules for efficiency. Experimental results show that the proposed direct resistance-estimation method allows the PV modules to achieve their maximum power and efficiency under various operation conditions.
关键词： Magnetic field,Solar cell,Series resistance,Shunt resistance,Grain size,Junction Recombination Velocity
更新于2025-09-12 10:27:22
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Measuring weak magnetic field via dissipatively coupled opto-mechanical system
摘要： In this paper, we propose a scheme for the detection of weak magnetic field based on dissipatively coupled optomechanical system. The system considered here is composed of a perfect mirror and a compound mirror formed by a Michelson-Sagnac interferometer (MSI) with a movable membrane. When the transmissivity of MSI is close to zero, it sensitively depends upon the position of membrane. Under this condition, the two mirrors results in an effective Fabry-Perot interferometer (FPI) whose linewidth depends upon the position of the membrane. We show that by applying current to the membrane in the presence of magnetic field, the position of the membrane changes which in turn changes the linewidth of the effective FPI. This change can be observed in the spectrum of the output field and consequently enables us to measure weak magnetic field. Thus an optical detection technique is proposed for the detection of weak magnetic field.
关键词： Michelson-Sagnac interferometer,weak magnetic field,dissipatively coupled optomechanical system,optical detection technique,Fabry-Perot interferometer
更新于2025-09-12 10:27:22
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Fabrication and characterization of quantum dot devices based on tetralayer graphene/hexagonal boron nitride heterostructures
摘要： We report on low temperature carrier transport property of quantum dot devices based on hexagonal boron nitride-encapsulated tetralayer graphene heterostructures. In the device with single dot geometry, we demonstrate a stochastic Coulomb blockade, suggesting formation of multiple dots coupled each other in series/parallel. Under a perpendicular magnetic field, the overlapping Coulomb diamonds are lifted at zero bias voltage and the charging energy is decreased. These imply the suppression of multiple dots behavior. Our results pave a way toward the investigation of interlayer correlation on single electron transport in few-layer graphene quantum dots.
关键词： magnetic field,hexagonal boron nitride,Coulomb blockade,tetralayer graphene,quantum dot
更新于2025-09-12 10:27:22
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Non-equilibrium electronic transport through a quantum dot with strong Coulomb repulsion in the presence of a magnetic field
摘要： The non-equilibrium electronic transport through a nanoscale device composed of a single quantum dot between two metallic contacts is studied theoretically within the framework of the Keldysh formalism. The quantum dot consists of a single energy level subject to an applied magnetic field. Correlations due to the Coulomb repulsion between electrons on the dot are treated with a Green’s function decoupling scheme which, although similar to the Hubbard-I approximation, captures some of the dynamics beyond. The scheme is exact in the so-called atomic limit, defined by vanishing tunneling between contacts and dot, and in the non-interacting limit, where the on-dot Coulomb repulsion is zero. Explicit analytic solutions, valid for arbitrary magnetic fields, are obtained for two important setups: (i) the stationary regime, with constant voltage bias between the leads, and (ii) the time-dependent regime for metallic leads with constant density of states of infinite width. In these regimes, the current through the dot is evaluated numerically for various parameter sets and its main features interpreted in terms of the underlying physical processes. The results are compared to the non-crossing approximation (NCA) and diagrammatic non-equilibrium quantum Monte-Carlo (QMC) where available.
关键词： Coulomb repulsion,magnetic field,non-equilibrium electronic transport,Hubbard-I approximation,non-crossing approximation,quantum dot,quantum Monte-Carlo,Keldysh formalism
更新于2025-09-12 10:27:22
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Magnetically Induced Depolarization of Microwave Scattering from a Laser-Generated Plasma
摘要： The e?ects of a local external magnetic ?eld on microwave scattering from a laser-generated plasma are investigated by modeling and experiment, leading to the prediction and observation of magnetically induced depolarization of scattered microwaves. The sample volume is localized by the small laser-generated plasma and depolarization is shown to depend on both the magnitude and direction of the magnetic ?eld; this indicates the potential for stando? detection and measurement of vector magnetic ?elds in gases.
关键词： laser-generated plasma,microwave scattering,depolarization,standoff detection,magnetic field
更新于2025-09-12 10:27:22