Two dimensional plasmons on the surface of piezocrystal

The coupled oscillations of two dimensional plasmons (TDP) and surface piezoacoustic wave are considered. The speed and damping of the waves depend on the surface charge density. A specific mechanism of damping of TDP is examined.     

Tunable hybrid surface waves supported by a graphene layer

We study electromagnetic waves localized near the surface of a semi-infinite dielectric medium covered by a graphene layer in the presence of a strong external magnetic field. We demonstrate that a novel type of hybrid TE-TM polarized surface plasmons can propagate along the graphene layer. We analyze the effect of the Hall conductivity on the polarization properties of these hybrid surface waves and suggest a possibility to tune the graphene plasmons by the external magnetic field.     

Plasma oscillations in nanotubes and the Aharonov-Bohm effect for plasmons

We theoretically analyze the collective oscillations of 2D electrons in nanotubes. In the presence of a magnetic field parallel to the tube axis, the plasmon frequencies undergo Aharonov-Bohm oscillations. The effect can manifest itself in infrared absorption and in Raman scattering. We calculate the cross sections for inelastic light scattering by plasmons.     

Plasmon mechanism of resistance magnetooscillations in a two-dimensional electron system in strong electric fields

A multielectron approach is developed to explain the resistance magnetooscillations in two-dimensional electron systems that have recently been detected under the action of microwave pumping [1] or a strong dc electric field [23]. A qualitative change in the screened impurity potential in a strong electric field is taken into account for the first time. When considered in the rest frame of the center of the cyclotron orbit, the impurity potential becomes nonstationary and, thus, should be screened dynamically. This fact substantially changes the picture of impurity scattering in a “pure” two-dimensional system: a dissipative current is induced by the excitation of two-dimensional plasmons rather than by one-electron transitions between the Landau levels. In the case of microwave pumping, every period of resistance oscillation in a reciprocal magnetic field is formed by the excitation of the corresponding magnetoplasmon branch, and the fine structure of oscillations is formed by the singularities of the magnetoplasmon density of states. In a “dirty” two-dimensional system, the role of electron-electron interaction weakens, collective excitations cease to exist, and the results transform into the well-known results obtained in terms of a one-electron approach.     

Electromagnetic renormalization of the plasmon spectrum in a laterally screened two-dimensional electron system

It is demonstrated theoretically that the effects of lateral electromagnetic screening of plasmons in a two-dimensional electron system by side metallic electrodes modify the plasmon spectrum. The effects of lateral screening become more pronounced at larger values of the plasmon wave vector. This leads to the deviation of the dispersion of laterally screened plasmons from the square-root dispersion law characteristic of unscreened plasmons. The results allow interpreting the recent experimental data of other authors on the dispersion of the plasma oscillations in a laterally screened two-dimensional electron system.     

Experimental determination of the mean free path of screened edge magnetoplasmons in a two-dimensional electron gas

Magnetic oscillations of the photovoltage in a two-dimensional electron system with the back gate, exposed to microwave radiation, are studied. The oscillations result from the interference of screened edge magnetoplasmons (EMPs). The mean free path of the EMPs is quantitatively determined by analyzing the dependence of the oscillation amplitude on the electron density. The dependences of the mean free path of the EMPs on the two-dimensional electron density, microwave frequency, electron relaxation time, and the magnetic field are studied. It is found that the dependences agree qualitatively with the known theoretical calculations.     

Spin waves on the surface of the nonferromagnetic nanotube in magnetic field

Propagating in the nonferromagnetic electron gas on the cylindrical nanotube's surface spin waves in longitudinal magnetic field are considered. The spectrum of electrons in the Hartree-Fock approximation was applied. The dynamic spin susceptibility of a degenerate electron gas was derived using the random phase approximation. The spectra of intra-subband and inter-subband magnons were calculated in quasiclassical and quantum limits. The quantity of spin waves spectrum branches depends on the amount of filled subbands. In case the filled subband numbers are large, the wave's frequencies undergo oscillations of de Haas-van Alphen and Aharonov-Bohm types with the electron density and the magnetic induction changes.     

Plasmas meet plasmonics

The term ‘plasmon’ was first coined in 1956 to describe collective electronic oscillations in solids which were very similar to electronic oscillations/surface waves in a plasma discharge (effectively the same formulae can be used to describe the frequencies of these physical phenomena). Surface waves originating in a plasma were initially considered to be just a tool for basic research, until they were successfully used for the generation of large-area plasmas for nanoscale materials synthesis and processing. To demonstrate the synergies between ‘plasmons’ and ‘plasmas’, these large-area plasmas can be used to make plasmonic nanostructures which functionally enhance a range of emerging devices. The incorporation of plasma-fabricated metal-based nanostructures into plasmonic devices is the missing link needed to bridge not only surface waves from traditional plasma physics and surface plasmons from optics, but also, more topically, macroscopic gaseous and nanoscale metal plasmas. This article first presents a brief review of surface waves and surface plasmons, then describe how these areas of research may be linked through Plasma Nanoscience showing, by closely looking at the essential physics as well as current and future applications, how everything old, is new, once again.     

Spatial fluctuations of the density of states in magnetic fields observed with scanning tunneling spectroscopy

Scanning tunneling spectroscopy images on n-InAs(110) exhibit a strong magnetic field dependent contrast on the 50 nm length scale, indicating fluctuations in the density of states of the sample. The contrast is correlated to previously observed Landau oscillations in dI/dV curves. Its origin is a spatial fluctuation of the Landau level energy of 3-4 meV caused by the inhomogeneous distribution of dopant atoms. Besides inducing large-scale fluctuations in the density of states, dopants preserve their ability to scatter electron waves. The resulting wave pattern is found to depend on the magnetic field. It is suggested that the dependence is guided by the condensation of the electronic states on Landau tubes.     

Field profiles of bulk plasmon polariton modes in layered systems containing a metamaterial

Electric and magnetic fields in a one-dimensional layered system that alternates air and a metamaterial are investigated. Special attention is devoted to frequencies of electric and magnetic bulk plasmons. It is shown that plasmon polaritons nearby such frequencies display field profiles concentrated in the metamaterial, where the field component parallel to the stacking direction is essentially uniform and dominates the perpendicular one.     

Quantization of plasma density irregularities under the action of a powerful electromagnetic wave: The spectrum of upper hybrid oscillations self-consistently trapped in density cavities

We present a theoretical model of the self-localization of the upper hybrid (UH) oscillations in plasma density depletions due to thermal nonlinearities driven by a homogeneous and monochromatic pump electric field. The Bohr-Sommerfeld condition for the trapped UH oscillations demands that the parameters of the density cavity be quantized. The depth and square of the depletion width across the magnetic field is proportional to an integer. The depth of the parabolically shaped cavity is proportional to the square of its width. The characteristic relative value of the density minimum is a few percent and the width is of the order of one meter for the pump wave amplitudes used in the ionospheric F-region experiments. We consider also the parametric decay of primary, localized UH oscillations trapped in the quantized plasma density depletions into secondary UH oscillations and lower-hybrid waves. We calculated the spectrum of the non-linear stabilized secondary UH oscillations which are also self-consistently trapped in the same density cavity. The spectrum of the UH oscillations is consistent with the observed spectrum of the downshifted (DM) and upshifted (UM) maximum in the stimulated electromagnetic emissions (SEE). Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 42, No. 7, pp. 641–650, July 1999.     

Nonlinear resonance of plasma waves in the thermal irregularities of ionospheric plasma

We study the effect of striction plasma density disturbances on the generation intensity of longitudional cold and plasma oscillations due to polarization of the magnetic field-aligned ionospheric plasma irregularities with δN_o<0 by a powerful radio wave. It is assumed that the plasma density level inside the irregularity intersects the upper-hybrid resonance level, in the vicinity of which the cold oscillations excited directly by a powerful radio wave are transformed to shorter-wave plasma oscillations. We consider the short plasma wave limit to reduce the problem to a system of two coupled equations for the cold wave induction and plasma wave electric field. The first equation is supplemented by a local source equal to the integral of the plasma wave electric field in the resonance region. The second equation involves the cold wave induction at the resonance point and describes the electric field of interacting waves in the resonance vicinity. We use simplifications connected with the small absorption of plasma waves propagating inside the irregularity and weak radiation of these waves outside the irregularity. These conditions correspond to the generation of eigenmodes of plasma oscillations trapped in the irregularity. We have obtained a resonance-type nonlinear equation for the electric field intensity (or energy flux) of eigenmode plasma waves with allowance for striction disturbances of the plasma density profile in the resonance region. It is shown that the striction expulsion of plasma is responsible for the occurrence of coefficients describing the change in the intensity of excitation and radiation of plasma waves at the irregularity boundary. Such an expulsion leads to variations of the efficient generation band of plasma eigenmodes with the total phase increment of the wave in the irregularity. It also leads to a change in the phase shift of the plasma wave reflected from the resonance. These coefficients and the nonlinear phase shift are expressed in terms of real wave functions of the nonlinear Airy equation which describes the electric field of the excited waves in the resonance vicinity when the dissipation is absent. Institute of Terrestrial Magnetism, Ionosphere and Radio Wave Propagation, Russian Academy of Sciences, Troitsk, Moscow region, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 41, No. 3, pp. 270–297, March, 1998.     

Plasma oscillations of massless Dirac electrons in a planar superlattice

The spectrum of plasma oscillations in a lateral superlattice of massless Dirac electrons has been calculated in the weak coupling approximation. The intensity of absorption of electromagnetic waves by plasmons of the superlattice at frequencies near the edges of band gaps has been found.     

Occurrence of a gap in the spectrum of magnetoplasma excitations of a two-dimensional electron disk subjected to a strong in-plane magnetic field

The effect of a parallel magnetic field on the dispersion of bulk and edge magnetoplasmons in a disk-shaped two-dimensional electron system is investigated. It is found that the anisotropy of the electron effective mass that appears in a parallel magnetic field lifts the degeneracy of plasma oscillations in the disk. This is accompanied by the occurrence of a gap in the spectrum of magnetoplasmons, and the magnetic dispersion of these excitations changes from a linear to a parabolic one. The width of the gap is determined by the difference between the frequencies of plasma oscillations along the field and transverse to the field and grows quadratically with the in-plane field strength.     

Nonlinear mixing of oppositely travelling surface plasmons

An analysis of the nonlinear mixing of oppositely travelling surface plasmons on a semi-infinite metal is discussed within the framework of Maxwell's equations. Coupling to free-space radiation fields, and transverse bulk waves in the metal is predicted under certain conditions at the sum frequency of the two surface plasmons.     

Dynamical behaviour of transverse plasmons in pair plasmas

This paper analytically investigates the nonlinear behaviour of transverse plasmons in pair plasmas on the basis of the nonlinear governing equations obtained from Vlasov--Maxwell equations. It shows that high frequency transverse plasmons are modulationally unstable with respect to the uniform state of the pair plasma. Such an instability would cause wave field collapse into a localized region. During the collapse process, ponderomotive expulsion is greatly enhanced for the increase of wave field strength, leading to the formation of localized density cavitons which are significant for the future experimental research in the interaction between high frequency electromagnetic waves and pair plasmas.     

低频Alfvén波对等离子体非共振加热与随机加热的粒子模拟

采用粒子模拟方法,研究沿背景磁场方向传播的低频Alfvén波对磁化等离子体加热的物理过程.模拟结果表明:离子在垂直和平行于背景磁场的方向都得到明显的加热,在非共振加热阶段,垂直方向比平行方向的加热效果更加显著,形成温度各向异性;在随机加热阶段,垂直和平行方向的温度最终达到饱和且趋于一致.加热过程中,离子所获得动力学温度的最大值由外加磁场能量密度与等离子体密度的比值决定,与Alfvén波的频率及振幅无关;离子在平行于背景磁场方向上被加速,并最终获得相当于Alfvén波相速度大小的流速.     

Theory of magnetic oscillations in Weyl semimetals

Weyl semimetals are a new class of Dirac material that possesses bulk energy nodes in three dimensions, in contrast to two dimensional graphene. In this paper, we study a Weyl semimetal subject to an applied magnetic field. We find distinct behavior that can be used to identify materials containing three dimensional Dirac fermions. We derive expressions for the density of states, electronic specific heat, and the magnetization. We focus our attention on the quantum oscillations in the magnetization. We find phase shifts in the quantum oscillations that distinguish the Weyl semimetal from conventional three dimensional Schrödinger fermions, as well as from two dimensional Dirac fermions. The density of states as a function of energy displays a sawtooth pattern which has its origin in the dispersion of the three dimensional Landau levels. At the same time, the spacing in energy of the sawtooth spike goes like the square root of the applied magnetic field which reflects the Dirac nature of the fermions. These features are reflected in the specific heat and magnetization. Finally, we apply a simple model for disorder and show that this tends to damp out the magnetic oscillations in the magnetization at small fields.     

Propagation of azimuthal waves along the surface of a metal current-carrying cylinder immersed into a magnetized plasma

It is shown that a metal current-carrying cylinder immersed into a cold magnetized plasma is a waveguide structure, in which coupled bulk ordinarily polarized and surface extraordinarily polarized waves can propagate along the azimuthal direction. Their interaction, stipulated by the fact that besides the longitudinal component, the external magnetic field has also a weak azimuthal component, is studied. Analytical expressions for the corrections to the eigenfrequency of these waves, stipulated by the effect of a constant azimuthal magnetic field, are obtained for the case of a uniform plasma density. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 51, No. 2, pp. 122–135, February 2008.