Spin-electron Acoustic Waves Research Articles

Hydrodynamics of quantum corrections to the Coulomb interaction via the third rank tensor evolution equation: application to Langmuir waves and spin-electron acoustic waves

The quantum effects in plasmas can be described by the hydrodynamics containing the continuity and Euler equations. However, novel quantum phenomena are found via the extended set of hydrodynamic equations, where the pressure evolution equation and the pressure flux third-rank tensor evolution equation are included. These give the quantum corrections to the Coulomb interaction. The spectra of the Langmuir waves and the spin-electron acoustic waves are calculated. The application of the pressure evolution equation ensures that the contribution of pressure in the Langmuir wave spectrum is proportional to $(3/5)v_{\textrm {Fe}}^{2}$ rather than $(1/3)v_{\textrm {Fe}}^{2}$ , where $v_{\textrm {Fe}}$ is the Fermi velocity.

Electrostatic Langmuir waves and spin-electron-acoustic waves in spin polarized plasma double layer

The quantum hydrodynamic model for the electrostatic wave in the two parallel layers of two dimensional electron gases is developed. It is considered for two regimes: classic regime and quantum regime with the separate spin evolution. There are two Langmuir-like waves in the classic regime. Their frequency (ω) dependencies have an interferencelike pattern on concentrations ω2∼(n01+n02 ± 2n01n02), where 01 and n02 are the equilibrium concentrations of the electrons in each layer of electron gas and ± refers to the spectrum of two waves. This spectrum appears instead of the couple of Langmuir waves in two noninteracting two-dimensional electron gases. In the quantum regime, the separate spin evolution leads to the spectrum of four waves instead of the two Langmuir waves present in two noninteracting two-dimensional electron gases. Two extra waves are related to the separate spin evolution of electrons. They are associated with the spin-electron acoustic waves. The contribution of the quantum Bohm potential has also been considered. The influence of the concentrations of electrons, the interlayer distance, and the spin polarization on the spectrum of waves is studied numerically.

Separate spin evolution of electrostatic energy flow in a degenerate quantum plasma

We have discussed energy densities and energy flow speed in a spin polarized plasma when longitudinal waves [Spin electron acoustic wave (SEAW) and Langmuir wave] propagate through the plasma. Employing the separate spin evolution quantum hydrodynamic model, we have derived the expression for energy densities and energy flow speed. It is found that the spin polarization changes the profiles of various energy densities. Specifically, we find that the spin polarization broadens the profile of the electrostatic energy density retaining the same peak value. In the case of kinetic and quantum energy densities, the profiles become narrower with the decrease in the peak value for the former case and increase for the latter. On the other hand, in the case of Langmuir waves, the spin polarization effect is similar for electrostatic energy density but opposite to the peak values of kinetic and quantum energy densities. The corresponding profiles become narrower as in the case of SEAW. Furthermore, energy flow speed associated with the SEAW and Langmuir wave is reduced for higher values of spin polarization. It is also noted that the contribution of Bohm potential in the dispersion compensates the reduction of energy flow due to spin polarization. The results are graphically analyzed for the choice of solid state plasma parameters.

Oblique propagation of longitudinal spin-electron acoustic waves under the influence of the Coulomb exchange interaction and the quantum Bohm potential

The influence of the exchange interaction on the properties of spin-electron acoustic waves at the oblique propagation of waves relative to the external magnetic field in the magnetically ordered metals is studied. The spectra of the Langmuir wave and the Trivelpiece-Gould wave is also considered. It is well-known that there are two branches of the spectrum of the spin-electron acoustic waves in this regime. The change of their properties under the influence of the exchange interaction is studied. The quantum Bohm potential is included either. The exchange interaction and the quantum Bohm potential give opposite contributions, but they do not compensate each other since they have different dependences on the wave vector. This competition creates a non-monotonical behavior of the Trivelpiece-Gould wave spectrum. The concavity changes in the monotonic spectra of the Langmuir wave and the SEAWs are found.

Oblique propagating extraordinary spin-electron acoustic waves

Spin-electron acoustic waves (SEAWs) are found in spin-polarized plasmas due to the separate spin evolution (SSE), where electrons with different spin projections are considered as two different species. The contribution of the transverse part of the electric field appears to be rather large in the extraordinary SEAW. Summing up all described above, we consider the extraordinary spin-electron acoustic waves at the oblique propagation relatively to the magnetic field direction. Our analysis shows that the SSE causes four oblique propagating waves. Two of them are reported earlier. Hence, we report about two extra waves which are purely oblique waves disappearing in the electrostatic limit. Extra solutions appear as the fine structure of two earlier reported waves.

Separated spin evolution quantum hydrodynamics of degenerate electrons with spin–orbit interaction and extraordinary wave spectrum

To consider the contribution of the spin–orbit interaction in the extraordinary wave spectrum we derive a generalization of the separate spin evolution quantum hydrodynamics. Applying the corresponding nonlinear Pauli equation we include the Fermi spin current contribution in the spin evolution. We find that the spectrum of extraordinary waves consists of three branches: two of them are well-known extraordinary waves and the third one is the spin-electron acoustic wave. A change of the extraordinary wave spectrum due to the spin–orbit interaction is also obtained.

On the upper hybrid wave instability in a spin polarized degenerate plasma

Applying the separate spin evolution-quantum hydrodynamic model incorporating Coulomb exchange interaction, the instabilities of upper hybrid mode and beam driven mode due to passing of electron beam in a spin polarized degenerate plasma are studied. It is found that the electron spin not only changes the growth rate of these modes but also gives birth to a new spin-dependent wave (spin electron acoustic wave) in the real frequency spectrum. Further, the Bohm potential and exchange interaction effects significantly affect the frequency spectra of upper hybrid mode. Other parameters like streaming speed of beam electron and beam density are also found to influence the growth rate of these modes. These consequential effects may have a strong bearing on the wave and instability phenomena in the solid state plasmas.

Extraordinary SEAWs under influence of the spin-spin interaction and the quantum Bohm potential

The separate spin evolution (SSE) of electrons causes the existence of the spin-electron acoustic wave. Extraordinary spin-electron acoustic waves (SEAWs) propagating perpendicular to the external magnetic field have a large contribution of the transverse electric field. Its spectrum has been studied in the quasi-classical limit at the consideration of the separate spin evolution. The spin-spin interaction and the quantum Bohm potential give contribution in the spectrum extraordinary SEAWs. This contribution is studied in this paper. Moreover, it is demonstrated that the spin-spin interaction leads to the existence of the extraordinary SEAWs if the SSE is neglected. It has been found that the SSE causes the instability of the extraordinary SEAW at the large wavelengths, but the quantum Bohm potential leads to the full stabilization of the spectrum.

Langmuir instability in partially spin polarized bounded degenerate plasma

Some new features of waves inside the cylindrical waveguide on employing the separated spin evolution quantum hydrodynamic model are evoked. Primarily, the instability of Langmuir wave due to the electron beam in a partially spin polarized degenerate plasma considering a nano-cylindrical geometry is discussed. Besides, the evolution of a new spin-dependent wave (spin electron acoustic wave) due to electron spin polarization effects in the real wave spectrum is elaborated. Analyzing the growth rate, it is found that in the absence of Bohm potential, the electron spin effects or exchange interaction reduce the growth rate as well as k-domain but the inclusion of Bohm potential increases both the growth rate and k-domain. Further, we investigate the geometry effects expressed by R and pon and find that they have opposite effects on the growth rate and k-domain of the instability. Additionally, how the other parameters like electron beam density or streaming speed of beam electrons influence the growth rate is also investigated. This study may find its applications for the signal analysis in solid state devices at nanoscales.

Kinetic description of the oblique propagating spin-electron acoustic waves in degenerate plasmas

An oblique propagation of the spin-electron acoustic waves in degenerate magnetized plasmas is considered in terms of quantum kinetics with the separate spin evolution, where the spin-up electrons and the spin-down electrons are considered as two different species with different equilibrium distributions. It is considered in the electrostatic limit. The corresponding dispersion equation is derived. Analysis of the dispersion equation is performed in the long-wavelength limit to find an approximate dispersion equation describing the spin-electron acoustic wave. The approximate dispersion equation is solved numerically. Real and imaginary parts of the spin-electron acoustic wave frequency are calculated for different values of the parameters describing the system. It is found that the increase in the angle between the direction of wave propagation and the external magnetic field reduces the real and imaginary parts of spin-electron acoustic wave frequency. The increase in the spin polarization decreases the real and imaginary parts of frequency either. The imaginary part of frequency has a nonmonotonic dependence on the wave vector which shows a single maximum. The imaginary part of frequency is small in comparison with the real part for all parameters in the area of applicability of the obtained dispersion equation.

Linear Analysis of Obliquely Propagating Longitudinal Waves in Partially Spin Polarized Degenerate Magnetized Plasma

Linear analysis of low frequency obliquely propagating electrostatic waves in a partially spin polarized degenerate magnetized plasma is presented. Using Fourier analysis, a general linear dispersion relation is derived for low frequency electrostatic lower hybrid (LH) wave, ion acoustic (IA) wave and ion cyclotron (IC) wave in the presence of electron spin polarization. It is found that the electron spin polarization gives birth to a new spin-dependent wave (spin electron acoustic wave) in the spectrum of these waves. Further, the electron spin polarization also causes drastic shifts in the frequency spectrum of these waves. These effects would have a strong bearing on wave phenomena in degenerate astrophysical plasmas.

Beam driven temporal growth and spatial amplification of electrostatic waves in a partially spin polarized degenerate magnetized plasma

The temporal growth and spatial amplification of electrostatic waves due to the interaction of an electron beam with a partially spin polarized degenerate magnetized plasma are studied. Using Fourier analysis, a generalized linear dispersion relation is derived for parallel propagating electrostatic waves in the presence of electron spin polarization. The electron spin polarization gives birth to a new spin-dependent wave (spin electron acoustic wave) in the real wave spectrum. Furthermore, increasing spin polarization reduces the temporal growth rate of the unstable mode. Regarding spatial amplification (magnitude of the imaginary wave number), it is found that spin polarization significantly affects the magnitude of both the real and the imaginary wave numbers. Additionally, how the various other parameters such as electron beam density, beam thermal speed, and streaming speed of the beam electron influence the temporal growth and spatial rates is also discussed. These effects would have a strong bearing on instability phenomena in the degenerate metallic and semiconductor plasmas and in astrophysical plasmas.

Non linear analysis of obliquely propagating spin electron acoustic wave in a partially spin polarized degenerate plasma

By employing the separated spin evolution quantum hydrodynamic model, non-linear evolution of obliquely propagating spin electron acoustic wave (SEAW) is presented. The solitary structures of SEAW is investigated through the Korteweg–de Vries (KdV) equation derived using reductive perturbation method. From the first order perturbations we derive the dispersion relation of SEAW and find that both the spin polarization and the propagation angle reduce the phase velocity while the electron streaming enhances it. Using small amplitude approximation, the solitary structure of SEAW is analyzed and the effects of spin polarization, propagation angle and electron streaming on the SEA soliton are studied. Our numerical results demonstrate that the spin polarization and the propagation angle play a balancing act on the soliton structures. The possible applications of our investigation to the astrophysical environments like white dwarfs is also discussed.

On a mechanism of high-temperature superconductivity: Spin-electron acoustic wave as a mechanism for the Cooper pair formation

We have found the mechanism of the electron Cooper pair formation via the electron interaction by means of the spin-electron acoustic waves. This mechanism takes place in metals with rather high spin polarization, such as ferromagnetic, ferrimagnetic, and antiferromagnetic materials. The spin-electron acoustic wave mechanism leads to transition temperatures 100 times higher than the transition temperature allowed by the electron-phonon interaction. Therefore, spin-electron acoustic waves give the explanation for the high-temperature superconductivity. We find that the transition temperature has strong dependence on the electron concentration and the spin polarization of the electrons.

Extraordinary spin-electron acoustic wave

The extraordinary waves in spin-1/2 quantum plasma are studied. The evolutions of spin-up and spin-down electrons are considered separately. Hence, the separate spin evolution quantum hydrodynamics is used as the tool of research. It is demonstrated that the spin polarization of electrons modifies the spectrum of the lower extraordinary wave (LEW). An increase of the frequency at the large wave vector due to the spin modified Fermi pressure is found for the cyclotron frequency smaller than the Langmuir frequency. Existence of the extraordinary spin electron acoustic wave (SEAW) is demonstrated. Spectrum of the extraordinary SEAW is calculated. This spectrum is located below the spectrum of the LEW for the cyclotron frequency smaller than the Langmuir frequency and the spectrum located between spectrums of the upper extraordinary wave and the LEW for the cyclotron frequency larger than the Langmuir frequency. Presence of the extraordinary SEAW spectrum in the area usually occupied by the LEW spectrum decre...

Extraordinary waves in two dimensional electron gas with separate spin evolution and Coulomb exchange interaction

Hydrodynamics analysis of waves in two-dimensional degenerate electron gas with the account of separate spin evolution is presented. The transverse electric field is included along with the longitudinal electric field. The Coulomb exchange interaction is included in the analysis. In contrast with the three-dimensional plasma-like mediums the contribution of the transverse electric field is small. We show the decrease of frequency of both the extraordinary (Langmuir) wave and the spin-electron acoustic wave due to the exchange interaction. Moreover, spin-electron acoustic wave has negative dispersion at the relatively large spin-polarization. Corresponding dispersion dependencies are presented and analyzed.

Spin-electron acoustic waves: The Landau damping and ion contribution in the spectrum

Separated spin-up and spin-down quantum kinetics is derived for more detailed research of the spin-electron acoustic waves (SEAWs). This kinetic theory allows us to obtain the spectrum of the SEAWs including the effects of occupation of quantum states more accurately than the quantum hydrodynamic theory. We derive and apply the quantum kinetic theory to calculate the Landau damping of the SEAWs. We consider the contribution of ions dynamics into the SEAW spectrum. We obtain the contribution of ions in the Landau damping in the temperature regime of classic ions. Kinetic analysis for the ion-acoustic, zero sound, and Langmuir waves at the separated spin-up and spin-down electron dynamics is presented as well.

Surface spin-electron acoustic waves in magnetically ordered metals

Degenerate plasmas with motionless ions show existence of three surface waves: the Langmuir wave, the electromagnetic wave, and the zeroth sound. Applying the separated spin evolution quantum hydrodynamics to half-space plasma, we demonstrate the existence of the surface spin-electron acoustic wave (SSEAW). We study dispersion of the SSEAW. We show that there is hybridization between the surface Langmuir wave and the SSEAW at rather small spin polarization. In the hybridization area, the dispersion branches are located close to each other. In this area, there is a strong interaction between these waves leading to the energy exchange. Consequently, generating the Langmuir waves with the frequencies close to hybridization area we can generate the SSEAWs. Thus, we report a method of creation of the spin-electron acoustic waves.

Rich eight-branch spectrum of the oblique propagating longitudinal waves in partially spin-polarized electron-positron-ion plasmas.

We consider the separate spin evolution of electrons and positrons in electron-positron and electron-positron-ion plasmas. We consider the oblique propagating longitudinal waves in these systems. Working in a regime of high-density n(0) ∼ 10(27) cm(-3) and high-magnetic-field B(0)=10(10) G, we report the presence of the spin-electron acoustic waves and their dispersion dependencies. In electron-positron plasmas, similarly to the electron-ion plasmas, we find one spin-electron acoustic wave (SEAW) at the propagation parallel or perpendicular to the external field and two spin-electron acoustic waves at the oblique propagation. At the parallel or perpendicular propagation of the longitudinal waves in electron-positron-ion plasmas, we find four branches: the Langmuir wave, the positron-acoustic wave, and a pair of waves having spin nature, they are the SEAW and the wave discovered in this paper, called the spin-electron-positron acoustic wave (SEPAW). At the oblique propagation we find eight longitudinal waves: the Langmuir wave, the Trivelpiece--Gould wave, a pair of positron-acoustic waves, a pair of SEAWs, and a pair of SEPAWs. Thus, for the first time, we report the existence of the second positron-acoustic wave existing at the oblique propagation and the existence of SEPAWs.

Spin-electron acoustic soliton and exchange interaction in separate spin evolution quantum plasmas

Separate spin evolution quantum hydrodynamics is generalized to include the Coulomb exchange interaction, which is considered as interaction between the spin-down electrons being in quantum states occupied by one electron. The generalized model is applied to study the non-linear spin-electron acoustic waves. Existence of the spin-electron acoustic soliton is demonstrated. Contributions of concentration, spin polarization, and exchange interaction to the properties of the spin electron acoustic soliton are studied.