scholarly journals Strongly direction-dependent magnetoplasmons in mixed Faraday–Voigt configurations

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Afshin Moradi ◽  
Martijn Wubs
Keyword(s):  
Magnetic Field ◽  
Dispersion Relation ◽  
Phase Velocity ◽  
Group Velocity ◽  
General Expression ◽  
Applied Magnetic Field ◽  
Electron Gas ◽  
Narrow Gap ◽  
Higher Symmetry ◽  
Energy Relations

AbstractThe electrostatic theory of surface magnetoplasmons on a semi-infinite magnetized electron gas is generalized to mixed Faraday–Voigt configurations. We analyze a mixed Faraday–Voigt type of electrostatic surface waves that is strongly direction-dependent, and may be realized on narrow-gap semiconductors in the THz regime. A general expression for the dispersion relation is presented, with its dependence on the magnitude and orientation of the applied magnetic field. Remarkably, the group velocity is always perpendicular to the phase velocity. Both velocity and energy relations of the found magnetoplasmons are discussed in detail. In the appropriate limits the known surface magnetoplasmons in the higher-symmetry Faraday and Voigt configurations are recovered.

Group velocity of wave propagation in carbon nanotubes

2008 ◽  
Vol 464 (2094) ◽  
pp. 1423-1438 ◽  
Author(s):  
Lifeng Wang ◽  
Wanlin Guo ◽  
Haiyan Hu
Keyword(s):  
Carbon Nanotubes ◽  
Cylindrical Shell ◽  
Dispersion Relation ◽  
Phase Velocity ◽  
Group Velocity ◽  
Continuum Mechanics ◽  
Flexural Wave ◽  
Multi Walled Carbon Nanotubes ◽  
Non Local ◽  
Walled Carbon Nanotubes

The group velocities of longitudinal and flexural wave propagations in single- and multi-walled carbon nanotubes are studied in the frame of continuum mechanics. The dispersion relations between the group velocity and the wavenumber for flexural and longitudinal waves, described by a beam model and a cylindrical shell model, are established for both single- and multi-walled carbon nanotubes. The effect of microstructures in carbon nanotubes on the wave dispersion is revealed through the non-local elastic models of a beam and a cylindrical shell, including the second-order gradient of strain and a parameter of microstructure. It is shown that the microstructures in the carbon nanotubes play an important role in the dispersion of both longitudinal and flexural waves. In addition, the non-local elastic models predict that the cut-off wavenumber of the dispersion relation between the group velocity and the wavenumber is approximately 2×10 10  m −1 for the longitudinal and flexural wave propagations in both single- and multi-walled carbon nanotubes. This may explain why the direct molecular dynamics simulation cannot give a proper dispersion relation between the phase velocity and the wavenumber when the wavenumber approaches approximately 2×10 10  m −1 , much lower than the cut-off wavenumber for the dispersion relation between the phase velocity and the wavenumber predicted by continuum mechanics.

Magnetoelastic Plane Waves in Infinite Rotating Media

1983 ◽  
Vol 50 (2) ◽  
pp. 283-287 ◽  
Author(s):  
S. K. Roy Choudhuri ◽  
L. Debnath
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Phase Velocity ◽  
Applied Magnetic Field ◽  
Plane Waves ◽  
Low Frequency ◽  
Phase Speed ◽  
Elastic Solid ◽  
Finite Conductivity ◽  
The Waves

A study is made of the propagation of magnetoelastic plane waves in an electrically conducting, infinite elastic solid permeated by a primary uniform magnetic field when the entire medium rotates with a constant angular velocity. A more general dispersion relation is obtained to investigate the effects of rotation and the external magnetic field on the phase velocity of the waves. This analysis reveals that when the applied magnetic field has both longitudinal and transverse components, the coupled magnetoelastic waves are dispersive and damped in an infinitely conducting medium in contrast to the nonrotating medium where the coupled waves are dispersive, but undamped. In the case of finite conductivity, the waves are dispersive and undamped in the absence of the applied magnetic field. At low frequency ω, the phase velocity of the waves varies as ω1/2 for finite conductivity, and is independent of the external magnetic field and rotation; while in the nonrotating case with low frequency (when the applied magnetic field has either longitudinal or transverse components) the phase speed is less than that in the rotating medium and is found to depend on the applied magnetic field. Also in both rotating and nonrotating cases, the phase velocity becomes very small for finitely conducting material with a very high magnetic permeability.

Convection of a weakly ionized plasma in a strong magnetic field: non-axisymmetric waves

1979 ◽  
Vol 22 (1) ◽  
pp. 187-191 ◽  
Author(s):  
Bhimsen K. Shivamoggi ◽  
Mahinder S. Uberoi
Keyword(s):  
Magnetic Field ◽  
Strong Magnetic Field ◽  
Applied Magnetic Field ◽  
Convective Instability ◽  
Narrow Gap ◽  
Azimuthal Direction ◽  
Central Electrode ◽  
Weakly Ionized ◽  
Weakly Ionized Plasma

Convective instability of a weakly ionized plasma contained in a narrow gap between two metal cylinders is studied considering non-axisymmetric waves. The case with the applied magnetic field in the azimuthal direction due to a central electrode is treated. The results show that the non-axisymmetric waves are more stable than their axisymmetric counterparts.

scholarly journals Резонансное поглощение электромагнитного излучения в монослое фосфорена

2019 ◽  
Vol 53 (4) ◽  
pp. 474
Author(s):  
В.В. Карпунин ◽  
В.А. Маргулис
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Absorption Coefficient ◽  
Electron Scattering ◽  
Applied Magnetic Field ◽  
Electron Gas ◽  
Single Layer ◽  
Radiation Frequency ◽  
Resonance Character ◽  
Account Electron

AbstractThe absorption coefficient of the electromagnetic radiation in a phosphorene single layer placed in a magnetic field is found. A degenerate and nondegenerate electron gas is considered. The resonant dependences of the absorptance on the radiation frequency and applied magnetic field are found. Taking into account electron scattering at an ionized impurity leads to oscillation dependences of the absorption coefficient on the radiation frequency and external magnetic field. The resonance character of the absorption curve is shown. The conditions of resonances and position of resonance peaks are found.

scholarly journals Neutrino Splitting and Density-Dependent Dispersion Relations

2012 ◽  
Vol 2012 ◽  
pp. 1-20 ◽  
Author(s):  
Emilio Ciuffoli ◽  
Jarah Evslin ◽  
Xiaojun Bi ◽  
Xinmin Zhang
Keyword(s):  
Dispersion Relation ◽  
Phase Velocity ◽  
Group Velocity ◽  
Modulational Instability ◽  
Dispersion Relations ◽  
Dispersive Media ◽  
Velocity Anomaly ◽  
Background Density ◽  
Quantum Analog ◽  
Splitting Process

We show that particles are unstable with respect to a splitting process, which is the quantum analog of the modulational instability in anomalous dispersive media, only when their group velocity exceeds their phase velocity. In the case of a neutrino, when the concavity results from a term E(P)~Pk, the neutrino will decay to two neutrinos and an antineutrino after traveling a distance proportional to E2+3k. Unlike the Cohen-Glashow instability, the splitting instability exists even if all particles involved in the interaction have the same dispersion relations at the relevant energy scales. We show that this instability leads to strong constraints even if the energy E is a function of both the momentum P and also of the background density ρ; for example, we show that it alone would have been sufficient to eliminate any model of the MINOS/OPERA velocity anomaly which modifies the neutrino dispersion relation while leaving those of other particles intact.

Acoustic wave propagation in orthorhombic media: Phase velocity, group velocity, and moveout approximations

Geophysics ◽  
2019 ◽  
Vol 84 (6) ◽  
pp. C269-C279 ◽  
Author(s):  
Mohammad Mahdi Abedi ◽  
Alexey Stovas ◽  
Yuriy Ivanov
Keyword(s):  
Wave Propagation ◽  
Dispersion Relation ◽  
Phase Velocity ◽  
Group Velocity ◽  
Practical Interest ◽  
Low Rank ◽  
Orthorhombic Symmetry ◽  
Explicit Equation ◽  
Velocity Equation ◽  
Kinematic Properties

An approximation is of practical interest whenever an exact approach is not available or is too complicated to be used. Kinematic properties of wave propagation in orthorhombic media are generally more complicated than in transversely isotropic media — an issue that emphasizes the necessity of proper approximate equations that keep a balance between accuracy and simplicity. Exact phase velocity equation in orthorhombic media is algebraically too complicated for some practical purposes, even after acoustic assumption. Although the exact phase velocity equation is readily calculated, there is not an explicit equation for the exact group velocity as a function of group angle nor for the traveltime as a function of offset. Accordingly, we have developed new approximate phase velocity, group velocity, and moveout equations for acoustic orthorhombic media in a simple and uniform functional form. They fit to their corresponding exact kinematic properties, within and outside the orthorhombic symmetry planes. We find a higher accuracy of our approximations compared with other existing approximations in a variety of orthorhombic models. As an example, we convert our phase velocity approximation to a dispersion relation in the frequency domain and use it for wavefield modeling in a heterogeneous orthorhombic model. Our dispersion relation is simpler and more accurate than the original equation being in use in the wave extrapolation modeling by low-rank approximation.

scholarly journals Hydrodynamic behaviour of velocity of applied magnetic field on unsteady MHD Couette flow of dusty fluid in an annulus

2021 ◽  
Vol 137 (1) ◽  
Author(s):  
Basant K. Jha ◽  
Dauda Gambo
Keyword(s):  
Magnetic Field ◽  
Phase Velocity ◽  
Skin Friction ◽  
Applied Magnetic Field ◽  
Hartmann Number ◽  
Fluid Phase ◽  
Dusty Fluid ◽  
Riemann Sum ◽  
Hydrodynamic Behaviour ◽  
Laplace Transform Technique

AbstractThis research work inspects mass transport phenomenon of Saffman’s dusty fluid model for transient magnetohydrodynamics fluid flow of a binary mixture passing through an annular duct. Particularly, effort has been devoted to theoretically explore the role of velocity of applied magnetic field. Here, our treatment of the governing momentum equations accountable for the flow is done using the classical Laplace transform technique and Riemann-Sum Approximation. The effects of the physical parameters such as time, relaxation time parameter, radii ratio, Hartmann number, variable mass parameter and velocity of applied magnetic field on the fluid phase velocity, dust phase velocity and skin friction have been illustrated pictorially. It is concluded that contrary to the known classical effect of boosting Hartmann number on velocity, both components of flow (fluid and dust phase) and skin friction are seen to be heightened with an overwhelming presence of velocity of applied magnetic field. For large time, it is anticipated that higher profiles for velocity and skin friction are seen with fluid phase and an accelerated moving wall.

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