共查询到20条相似文献,搜索用时 531 毫秒
1.
Band gap characteristics of plasma with periodically varying external magnetic field 总被引:1,自引:0,他引:1
The reflectance characteristics of a one-dimensional periodically magnetized plasma structure is studied by using the transfer matrix method. It is found that this system has the band gap characteristics of photonic crystals, so we also name it a plasma photonic crystal. The results show that the gap location and gap width can be controlled by the incident angle. If the external magnetic field is small, the gap location and gap width change significantly with incident angle, while they change only slightly when the external magnetic field is sufficiently large. The collision frequency has little effect on the gap location and gap width while it makes the amplitude of reflectance and transmission decrease. This new type of plasma photonic crystal could have potential applications in designing tunable photonic crystal devices. 相似文献
2.
经典理论所描述的电场和磁场处处同相的平面电磁波模并不存在.Maxwell方程组的解依赖于 电磁场的初始值或边界条件,根据不同的初始条件解得的平面电磁波模是不同的.结果表明 ,平面电磁波是横波,在不同的位置,由变化的电场激发的磁场或由变化的磁场激发的电场 振幅不同,电场与磁场的相位差也不同.
关键词:
Maxwell方程组
最优微分方程
初始条件
平面电磁波 相似文献
3.
This paper proposes a tunable zeroth-order resonator on a composite right/left-handed transmission line consisting of a transversely magnetized ferrite substrate periodically loaded by microstrip inductors. Based on the propagation theory of edge guided modes, the analysis procedure of this structure is introduced. The numerical results demonstrate the tunability of the resonant frequency by changing the DC bias magnetic field applied to the ferrite. In contrast to previous work, the proposed structure is easy to design and fabricate and does not require a chip component. 相似文献
4.
In this letter, we have studied the influence of the external magnetic fields on tunneling of the spin-1 Bose
condensate. We find that the population transfer between spin-0
and spin-±1 exhibits the step structure under the external
cosinusoidal magnetic field and a combination of static and
cosinusoidal one, respectively. Compared with the longitudinal
component of the external magnetic field, the smaller the
transverse component of the magnetic field is, the larger the
time scale of exhibiting the step structure does. The tunneling
current may exhibit periodically oscillation behavior when the
ratio of the transverse component of the magnetic field is smaller
than that of the longitudinal component, otherwise it exhibits a
damply oscillating behavior. This means that the dynamical spin
localization can be adjusted by the external magnetic fields. 相似文献
5.
M. Gorkunov M. Lapine E. Shamonina K.H. Ringhofer 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,28(3):263-269
Effective magnetic properties of a composite meta-material consisting of periodically arranged circular conductive elements
are studied theoretically. A general expression for the effective bulk permeability is obtained with mutual effects and lattice
ordering being taken into account. The resonance frequency of the permeability is found to be strongly dependent on the size
and shape of the unit cell. Frequency dispersion of the permeability is studied with special attention paid to the frequency
range, where negative values of the permeability are possible. Corresponding recommendations for optimisation of the meta-materials
with negative permeability are made. The results are confirmed by numerical simulations of the finite structure behaviour
in an external magnetic field.
Received 19 April 2002 Published online 31 July 2002 相似文献
6.
7.
8.
Two-photon interband magnetoabsorption in InSb has been studied by measuring the resulting changes in the photoconductivity and free-hole absorption as a function of magnetic field and incident photon energy. In both the photoconductivity and transmission measurements, resonant structure with the peaks occuring at the same values of magnetic field was observed with the incident light polarized both parallel and perpendicular to the magnetic field. The results thus are not in agreement with the existing theories of two-photon magnetoabsorption. A modification to a perturbation theory approach is suggested that appears to explain the experimental observations. 相似文献
9.
Electron transport across a quantum wire embedding a saw-tooth superlattice 总被引:1,自引:0,他引:1 下载免费PDF全文
By developing the recursive Green function method, the transport properties through a quantum wire embedding a finite-length saw-tooth superlattice are studied in the presence of magnetic field. The effects of magnetic modulation and the geometric structures of the superlattice on transmission coefficient are discussed. It is shown that resonant peak splitting of this kind of structure is different from that of ‘magnetic' and ‘electric' superlattices in two-dimensional electron gas. The transmission spectrum can be tailored to match requirements through adjusting the size of saw-tooth quantum dot and field strength. 相似文献
10.
设计并制作了一种马赫-曾德尔干涉仪(Mach-Zehnder Interferometer,MZI)与光纤布喇格光栅级联的光纤磁场传感器,其中MZI由相当于分光器的锥结构和相当于耦合器的花生锥结构级联组成,封装在填充了磁流体的毛细管中.由于磁流体的有效折射率会随着外界磁场强度的改变而变化,故可通过观察干涉谱的特征波长的变化来测量外界磁场强度,而光纤布喇格光栅透射峰对磁场强度不敏感.当磁场强度由0mT变化到20mT时,马赫-曾德尔干涉峰的灵敏度为0.11nm/mT.温度特性实验测得马赫-曾德尔干涉峰和光纤布喇格光栅透射峰的温度灵敏度分别为0.401 5nm/℃和0.011 4nm/℃.因此,可利用敏感矩阵实现双参量同时测量. 相似文献
11.
T. Meier P. Thomas S.W. Koch 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,22(2):249-256
Linear and nonlinear optical absorption spectra are studied theoretically for semiconductor nanorings penetrated by a magnetic
field. Due to the Aharanov-Bohm effect the spectral position as well as the oscillator strength of the exciton change periodically
as function of the magnetic flux enclosed by the ring. In the nonlinear differential absorption spectra it is found that the
magnetic field strongly modifies Coulomb many-body correlations. In particular, the magnetic-field-induced increase of the
exciton binding energy is accompanied by a decrease of the biexciton binding energy. The persistence of these effects in the
presence of energetic disorder is analyzed.
Received 31 January 2001 相似文献
12.
We theoretically investigate the electron transport properties in a non-magnetic heterostructure with both Dresselhaus and Rashba spin-orbit interactions. The detailed-numerical results show that (1) the large spin polarization can be achieved due to Dresselhaus and Rashba spin-orbit couplings induced splitting of the resonant level, although the magnetic field is zero in such a structure, (2) the Rashba spin-orbit coupling plays a greater role on the spin polarization than the Dresselhaus spin-orbit interaction does, and (3) the transmission probability and the spin polarization both periodically change with the increase of the well width. 相似文献
13.
The aggregation and rearrangement of nanoparticles embedded in a thin cell of ferrofluid at various applied magnetic fields was studied by Monte Carlo simulation. Regular microcolumns with the axis parallel to the magnetic field were observed with column size and spacing depending on the ramp speed of the applied field. Our model successfully simulated the reported experimental results that the column size decreases as the ramp speed increases, which is attributed to the diminishing time to achieve the final assembled state at a given final magnetic field. Column arrays of tunable lattice constants characterizing various spectroscopic dispersions are elucidated. The hexagonal structure of the aggregation of magnetic nanoparticles and optical dispersion were observed through an optical microscope. The transmission diffraction spectra depending on column spacings and sizes of the column array are simulated to yield results comparable to the experiment. 相似文献
14.
《Physica E: Low-dimensional Systems and Nanostructures》2009,41(10):3155-3159
The spin transport of holes through a quantum wire made of many identical T-shaped diluted magnetic semiconductor/semiconductor units is investigated theoretically. The spin-down and spin-up transmission coefficients have been studied as a function of stub parameters. The spin-up transmission coefficient as a function of the stub length is extremely negligible, in the case of multiple-stub quantum wire, while the spin-down transmission coefficient shows a nearly periodic behaviour with regions of large transmission separated by forbidden bands. The spin polarization switches periodically between one and zero as the stub length is changed and shows a square-wave pattern. 相似文献
15.
根据10 kV紧凑型三相同轴高温超导电缆参数,在COMSOL Multiphysics有限元软件中建立电缆的二维仿真模型,基于H方程求解了电缆在额定工况稳态运行时以及不同传输电流下的磁场分布和交流损耗;在此基础上,分析了绕制半径、相间距离以及相间相对角度对交流损耗的影响.仿真结果表明,各相超导层绕制半径越小,相间距离越小,各相产生的交流损耗越小;三相的交流损耗有随着超导层结构周期性变化的特点,且当相间相对角度为0°时,各相产生的交流损耗最大. 相似文献
16.
A. A. Shtygashev 《Physics of the Solid State》2011,53(5):1025-1032
The method and results of calculating the coefficient of transmission of a circular ultrasound wave through a multilayer ferromagnet/nonmagnet dielectric system with allowance for excitation of spin waves in magnetic layers are presented. The dependence of the resonance structure of the transmittance spectrum on the number of layers and the magnetic field strength has been studied. 相似文献
17.
Prabhakaran Letha Premlal Dinesh Chandra Tiwari Vandana Chaturvedi 《The European Physical Journal B - Condensed Matter and Complex Systems》2018,91(5):78
We present a detailed theoretical analysis about the influence of surface polaritons on the transmission properties of electromagnetic waves at the periodically corrugated interface between the vacuum and left-handed material by using nonlinear boundary condition approach. The principle behind this approach is to match the wave fields across the grating interface by using a set of linear wave equation with nonlinear boundary conditions. The resonant transmission of the incident electromagnetic radiation in this structure is feasible within a certain frequency band, where there is a range of frequency over which both the electric permittivity and the magnetic permeability are simultaneously negative. The enhanced transmission is attributed to the coupling of the incident electromagnetic wave with the excited surface polaritons on grating interface. Finally, we present the numerical results illustrating the effect of the structural parameters and angle of incidence on the transmission spectra of a TM polarized electromagnetic wave. 相似文献
18.
The reflection coefficient of bulk spin waves from a ferromagnetic multilayer with periodically modulated parameters of the
exchange interaction, the uniaxial magnetic anisotropy and the saturation magnetization (a magnonic crystal) is calculated.
The dependence of the reflection coefficient upon the spin wave frequency and the values of the bias magnetic field, the parameter
of interfacial coupling, and the internal structure of the unit cell are investigated.
相似文献
19.
Photon-assisted and spin-dependent shot noise in magnetic-field tunable ZnSe/Zn_(1-x)Mn_xSe structures 下载免费PDF全文
We have investigated the photon-assisted shot noise properties in the magnetic field tunable heterostructures. Transport properties of the model structure are strongly dependent on the oscillatory field and the magnetic field. In this structure,electrons can absorb or emit one or multi-photons to reach the quasi-bound state. As a result, the transmission properties are affected considerably by photon-assisted tunneling and these features cause the nontrivial variations in the shot noise and Fano factor. It is found that the shot noise becomes spin-dependent and can be modulated not only by the magnetic field, but also by the oscillatory field. Both the spin-up and spin-down components of the shot noise can be greatly suppressed by the magnetic field, and can also be drastically enhanced by the harmonically driven field. Furthermore,with increasing external magnetic field, it is important to note that the enhanced intensity is decreased, even suppressed.These results suggest another method to suppress the shot noise via modulating the oscillatory field at a diluted-magneticsemiconductors/semiconductor structure. 相似文献
20.
Interaction of traveling electromagnetic waves with MBE-grown Fe/Cr multilayer nanostructures is studied. Measurements are
made in the frequency range 5.7–12.5 GHz at magnetic fields of up to 32 kOe. It is found that the dependence of the microwave
transmission coefficient on the external magnetic field intensity is similar to the field dependence of the dc giant magnetoresistive
effect. As a result of the interaction, the wavenumber varies in proportion to the electrical resistance of the structure.
A simulation of the magnetic fields shows that the microwave currents flow largely across the multilayer nanostructure (normally
to the layers). 相似文献