共查询到20条相似文献,搜索用时 31 毫秒
1.
We theoretically study the resonant transmission of electromagnetic waves at the THz frequencies through subwavelength semiconductor
slits under external static magnetic fields. The dispersion relations of the surface plasmon polaritons (SPPs) inside a subwavelength
slit are analytically derived. It is found that the SPPs propagating along one direction and its reverse are symmetric when
parallel external magnetic fields are applied, but are asymmetric when antiparallel external magnetic fields are applied.
The transmission properties of periodic subwavelength semiconductor slit arrays with the antiparallel magnetic fields in each
unit cell are investigated by the mode expansion technique. The two significant transmission characteristics are observed:
(i) The resonant peaks are redshifted with increasing external magnetic fields; (ii) The transmissions in the two opposite
directions through the slit arrays are asymmetric. The origin of the transmission asymmetry is reasonably explained by the
magnetic-field induced asymmetric SPP propagation losses. 相似文献
2.
3.
Accounting for the modified orbits of plasma particles due to constant external electric and magnetic fields, a general expression for the velocity space diffusion tensor of a turbulent plasma is derived. The nonlinear frequency shift and the anomalous resistivity in the presence of external fields are calculated. It is shown that the effect of a strong external electric field on the frequency shift is to reduce its magnitude. Furthermore, the dependence of the anomalous resistivity on the external magnetic field is obtained. 相似文献
4.
对半掺杂氧化钴Pr0.5Sr0.5CoO3在居里温度附近的磁熵变进行了研究。研究表明,磁熵变的最大值依赖于外磁场强度;半高宽也与磁场强度有关;相对制冷能力与磁场强度几乎呈线性关系。另外,在不同的温度和磁场强度下测得的磁熵变能够重新标度为一条普适的曲线。依据该唯象的普适曲线,能够较准确的计算出在不同温度和磁场强度下磁熵变的大小。 相似文献
5.
对半掺杂氧化钴Pr0.5Sr0.5Co O3在居里温度(TC≈232 K)附近的磁熵变(ΔSM)进行了研究.研究表明,磁熵变的最大值(ΔSmaxM)依赖于外磁场强度(H):ΔSmaxM~Hn,其中n=0.55±0.14;半高宽(δTFWHM)与H有如下关系:δTFWHM~H0.4±0.1;而相对制冷能力(RCP)与H几乎呈线性关系.另外,在不同的温度和磁场强度下测得的磁熵变(ΔSM(T,H))能够重新标度为一条普适的曲线.依据该唯象的普适曲线,能够较准确的计算出在不同温度和磁场强度下磁熵变的大小. 相似文献
6.
K.-F. Braun S. Sievers M. Albrecht U. Siegner K. Landfester V. Holzapfel 《Journal of magnetism and magnetic materials》2009,321(22):3719-3725
We investigate the effect of external magnetic fields on the magnetic structure of thin films from magnetic nanoparticles (MNP) with dipolar interaction. Such fields are present, for example, if samples are scanned with magnetic probes. Numerical simulations and experimental magnetic force microscopy (MFM) studies are presented. Numerically, we have calculated the magnetization pattern of single-layer and multilayer MNP thin films. The calculations show that unperturbed single-layer MNP films have an in-plane orientation of the magnetization with a flux-closure-domain pattern. An external field generated by a point dipole above the film induces locally an out-of-plane configuration of the magnetization. In the corresponding MFM images, the domain pattern in the film is erased and a stripe-like contrast enhancement at the edges appears. Multilayer films are found to be more robust against external fields than monolayers. 相似文献
7.
M. S. Dvornikov 《Physics of Atomic Nuclei》2007,70(2):342-348
Spin-flavor oscillations of neutrinos in rapidly varying external fields are studied. A method for describing neutrino oscillations in arbitrary rapidly varying external fields is developed. An effective Hamiltonian that describes the evolution of the averaged neutrino wave function is obtained. Neutrino oscillations in rapidly varying magnetic fields are considered on the basis of the general formalism developed in this study. Neutrino transitions in a superposition of a constant and a rotating (in space) magnetic field that are transverse with respect to the neutrino velocity are studied. The probabilities of transitions in spin-flavor oscillations of neutrinos in the magnetic fields of the Sun are estimated. Numerical solutions to the Schrödinger equation for the Hamiltonian that describes neutrino interaction with a constant and a rotating (in space) magnetic field are given. It is shown that the approximate analytic formula obtained in the present study for the probability of neutrino transitions is consistent with the respective numerical solution to the evolution equation at high frequencies of the rotating magnetic fields. 相似文献
8.
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
9.
A gap in the spectrum of spin and ferroelectric waves is investigated versus magnetic and electric fields. It is demonstrated
that the magnetoelectric interaction is amplified with increasing external magnetic field and is weakened with increasing
external electric field. This allows the interaction between the spin and ferroelectric subsystems to be controlled by external
fields.
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 43–47, February, 2009. 相似文献
10.
We report the first experimental observation of optical linear birefringence induced in molecular liquids by crossed electric and magnetic fields perpendicular to the direction of light propagation. The optical axes coincide with the external fields, and the strength is bilinear in the electric and magnetic fields. 相似文献
11.
We study theoretically the effect of weak external magnetic fields on persistent spin helix states in semi- conductor two-dimensional electron gases with both Rashba and linear-in-momentum Dresselhaus spin-orbit coupling. We show that in the presence of weak external magnetic fields, some basic properties of a persistent spin helix state, including the dispersion relation between the decay time and the magnitude of the wavevector, the maximum decay time and the value of the characteristic magnitude of the wavevector at which the maximum decay time occurs, will all depend sensitively on the directions of applied external magnetic fields. 相似文献
12.
Da-Chuang Li 《Optics Communications》2009,282(6):1226-1636
Thermal entanglement is investigated in a two-qubit Heisenberg XYZ system with different inhomogeneous magnetic fields. It is found that different magnetic fields have different entanglement and critical values. In addition, according to the relation of spin-spin coupling coefficients, a more efficient control parameter of magnetic field can be obtained by adjusting the direction of external magnetic field. 相似文献
13.
The application of magnetic fields, electric fields, and the increase of the electromagnetic wave frequency are up-and-coming solutions for the blackout problem. Therefore, this study considers the influence of the external magnetic field on the electron flow and the effect of the external electric field on the electron density distribution, and uses the scattering matrix method (SMM) to perform theoretical calculations and analyze the transmission behavior of terahertz waves under different electron densities, magnetic field distributions, and collision frequencies. The results show that the external magnetic field can improve the transmission of terahertz waves at the low-frequency end. Magnetizing the plasma from the direction perpendicular to the incident path can optimize the right-hand polarized wave transmission. The external electric field can increase the transmittance to some extent, and the increase of the collision frequency can suppress the right-hand polarized wave cyclotron resonance caused by the external magnetic field. By adjusting these parameters, it is expected to alleviate the blackout phenomenon to a certain extent. 相似文献
14.
为了提高微波等离子推力器性能,改善等离子体对电磁波能量的吸收状况,提高核心区温度,提出外加磁场的方案,并对热等离子体进行了数值模拟.假设局域热平衡条件,采用Navier-Stokes,Maxwell和Saha方程,利用压力修正的半隐格式和时域有限差分求解方法,建立了径向磁镜场下推力器内等离子体流场的数值计算模型.数值模拟结果表明:外加磁场后的磁感应强度小于0.5 T时,推力器内热等离子体核心区最高温度随磁感应强度的增加而迅速提高.外加磁场后的磁感应强度大于0.5 T时,核心区最高温度随磁感应强度的增加而缓慢提高.磁感应强度为0.5 T时,热等离子体核心区最高温度与不加磁场相比提高了24%.外加磁场对等离子体流场速度分布影响不大.
关键词:
等离子体模拟
等离子体相互作用
等离子体流动 相似文献
15.
In setting up field-cycling experiments aimed to study physical phenomena in the low-field region, magnetic field contributions from external sources (earth’s field, environment, other magnets, etc.) become important. Indeed, a compensation of these contributions has successfully been used for the application of field-cycling methods to nuclear magnetic relaxation and double resonance experiments. This feature becomes relevant in samples where local fields are stronly averaged due to motional narrowing, on the ground that relaxation experiments can therefore be extended to lower fields. Compensation of external contributions is also crucial for the study of kinky processes related to internal local fields. In this article we outline NMR field-cycling experiments aimed to detect and quantify the external net magnetic field sensed by the spin-system. Both parallel and normal components with respect to the high-field Zeeman axis can be determined separately by using different experimental protocols. 相似文献
16.
Yu. I. Klimenko 《Russian Physics Journal》1974,17(11):1481-1485
A covariant spin operator is found for fermions with anomalous magnetic and electric dipole moments in constant external fields. The spin behavior of a neutral fermion in constant magnetic and electric fields is investigated using exact solutions obtained for the Dirac equation. 相似文献
17.
Dimitar Bakalov 《Hyperfine Interactions》2009,194(1-3):21-27
The spin structure of the (37,35) energy level of antiprotonic helium-4 in permanent homogenous external magnetic field has been calculated in first order of perturbation theory. For weak magnetic fields the effect is observed as an additional broadening of the spectral lines. For magnetic fields of the order of kG and higher, the magnetic and hyperfine interactions become comparable to each other, and the hyperfine spectrum is rearranged. 相似文献
18.
Shengli Pu Tao Geng Xianfeng Chen Xianglong Zeng Ming Liu Ziyun Di 《Journal of magnetism and magnetic materials》2008
The model of tunable superparamagnetic photonic crystals self-assembled in colloidal magnetic fluids under externally applied magnetic fields is established. The mechanisms, which are in charge of the tunability of the band gaps with magnetic fields are clarified. The band structures of the triangularly-arrayed two-dimensional photonic crystals with limited heights of magnetic columns are calculated with the experimental data of structures and refractive indices in the literatures. The field-dependent properties of the first band gaps are gained for the z-odd and z-even modes, respectively. Simulation results indicate that the mid frequencies of the first band gaps of the z-odd modes can be easily tuned by the external magnetic fields, while those of the z-even modes bear relatively weak dependence on the external magnetic fields. Simultaneously, the first band gaps of both kinds of modes become wide along with the increase of the magnetic fields. The results presented in this work give a guideline for realizing the tunable photonic crystals with magnetically colloidal materials and magnetic stimuli. 相似文献
19.
F. Xu X. Chen X.Y. Zhang C.K. Ong 《Journal of magnetism and magnetic materials》2010,322(21):3262-3265
Analysis shows that it is possible to make use of dispersed magnetic ripple fields to obtain a wide frequency linewidth of permeability spectra of soft magnetic thin films. As-sputtered FeCoN thin film sputtered on flexible Kapton substrate is studied as an example. It has ultrawide frequency linewidths of its resonance peaks in the permeability spectra, compared to its counterpart deposited on Si substrate. The frequency linewidth of FeCoN on Kapton substrate decreases with external magnetic field, showing a different field dependence from that of FeCoN on Si substrate. The ultrawide frequency linewidth and its decrease with external magnetic field are ascribed to the dispersed magnetic ripple fields caused by the flexible substrate. This work shows that the flexible substrate is effective in obtaining a wide frequency linewidth of the permeability spectra of soft magnetic thin films. 相似文献
20.
The entanglement in one-dimensional random XY spin systems where the impurities of exchange couplings and the external magnetic fields are considered as random variables is investigated by solving the different spin-spin correlation functions and the average magnetization per spin. The entanglement dynamics near particular locations of the system is also studied when the exchange couplings (or the external magnetic fields) satisfy three different distributions (the Gaussian distribution, double-Gaussian distribution, and bimodal distribution). We find that the entanglement can be controlled by varying the strength of external magnetic field and the distributions of impurities. Moreover, the entanglement of some nearest-neighbouring qubits can be increased for certain parameter values of the three different distributions. 相似文献