Norman J. Morgenstern Horing

Absorption of terahertz radiation by plasmon modes in a grid-gated double-quantum-well field-effect transistor

The terahertz absorption spectrum of plasmon modes in a grid-gated double-quantum-well (DQW) field-effect transistor structure is analyzed theoretically and numerically using a first principles electromagnetic approach and is shown to faithfully reproduce important physical features of recent experimental observations. We find that the essential character of the response—multiple resonances corresponding to spatial harmonics of standing plasmons under the metal grating—is caused by the static spatial modulation of electron density in the channel. Higher order plasmon modes become more optically active as the depth of the electron density modulation in the DQW tends towards unity. The maximum absorbance, at plasma resonance, is shown to be 1/2. Furthermore, the strongest absorption also occurs when the standing plasmon resonance coincides with the fundamental dipole mode of the ungated portion of the channel.

Introduction to complex plasmas

Complex Plasmas.- Classical and Quantum Plasmas.- Principles of Transport in Multicomponent Plasmas.- to Quantum Plasmas.- to Quantum Plasma Simulations.- Quantum Effects in Plasma Dielectric Response: Plasmons and Shielding in Normal Systems and Graphene.- Strongly Coupled and Dusty Plasmas.- Imaging Diagnostics in Dusty Plasmas.- Structure and Dynamics of Finite Dust Clusters.- Statistical Theory of Spherically Confined Dust Crystals.- PIC-MCC Simulations of Capacitive High-Frequency Discharge Dynamics with Nanoparticles.- Molecular Dynamics Simulation of Strongly Correlated Dusty Plasmas.- Reactive Plasmas, Plasma-Surface Interaction, Technological Applications.- Nonthermal Reactive Plasmas.- Formation and Deposition of Nanosize Particles on Surfaces.- Kinetic and Diagnostic Studies of Molecular Plasmas Using Laser Absorption Techniques.- X-Ray Diagnostics of Plasma-Deposited Thin Layers.- The Use of Nonthermal Plasmas in Environmental Applications.- Complex (Dusty) Plasmas: Application in Material Processing and Tools for Plasma Diagnostics.

Quantum theory of electron gas plasma oscillations in a magnetic field

Abstract The response function (inverse dielectric function) for an electron gas in an external magnetic field is investigated by the method of Greens functions using the random phase approximation. The spectrum of plasma oscillations, and associated damping, are obtained. In particular, for wave vector p perpendicular to the magnetic field the dispersion relation is studied as a power series in p2, and is shown to contain oscillatory terms of the de Haas-van Alphen type in the degenerate case, and quantum dynamical corrections through the parameter ℏωcβ in the nondegenerate case. A Mittag-Leffler expansion of this dispersion relation shows that integral multiples of the cyclotron frequency are forbidden, and there are an infinite number of plasma modes (resonances), one in each interval [nωc, (n + 1)ωc]. A semiclassical model is worked through in detail, and the frequencies of these undamped plasma modes are calculated when p 2 (ζ or 1 β ) mω c 2 ⪢ 1 (low magnetic field). The gaps in the frequency spectrum are calculated. Likewise the excitation amplitudes of the various modes are calculated. “Phase mixing” of the modes (resonances) is considered for small ωc, and is seen to result in a single damped plasma mode at Ω ∼ ω p , as one should expect. The dispersion relation for wave vector p having arbitrary direction with respect to the magnetic field is studied as a power series in p2, and again oscillatory terms of the de Haas-van Alphen type are found in the degenerate case. Known nondegenerate results bearing quantum dynamical corrections through the parameter ℏωcβ are verified. The semiclassical model is employed to calculate angular corrections to the plasma modes (resonances) in the intervals [nωc, (n + 1)ωc] for small angular departures from the case of perpendicular propagation, θ ⪡ 1, when p 2 (ζ or 1 β ) mω c 2 ⪢ 1 . The excitation amplitudes of all the plasma modes considered are calculated. Detailed formulas for natural damping, which take full account of the influence of the magnetic field, are given for all the plasma modes considered. These reduce to known results in the nondegenerate case and the field free degenerate case. They show clearly the effects of the field on damping in the degenerate case, and the role of oscillatory terms in the de Haas-van Alphen sense is investigated.

Quantum theory of longitudinal dielectric response properties of a two-dimensional plasma in a magnetic field

Abstract An analysis of dynamic and nonlocal longitudinal dielectric response properties of a two-dimensional Landau-quantized plasma is carried out, using a thermodynamic Greens function formulation of the RPA with a two-dimensional thermal Greens function for electron propagation in a magnetic field developed in closed form. The longitudinal-electrostatic plasmon dispersion relation is discussed in the low wavenumber regime with nonlocal corrections, and Bernstein mode structure is studied for arbitrary wavenumber. All regimes of magnetic field strength and statistics are investigated. The class of integrals treated here should have broad applicability in other two-dimensional and finite slab plasma studies. The two-dimensional static shielding law in a magnetic field is analyzed for low wavenumber, and for large distances we find V( r ) ∼ Q k 0 2 r 3 . The inverse screening length k 0 = 2πe 2 ∂ϱ ∂ξ (ϱ = density, ξ = chemical potential) is evaluated in all regimes of magnetic field strength and all statistical regimes. k0 exhibits violent DHVA oscillatory behavior in the degenerate zero-temperature case at higher field strengths, and the shielding is complete when ξ = r′ l z.shtsls; ω , but there is no shielding when ξ ≠ r′ l z.shtsls; ω c . A careful analysis confirms that there is no shielding at large distances in the degenerate quantum strong field limit l z.shtsls; ω c > ξ . Since shielding does persist in the nondegenerate quantum strong field limit l z.shtsls; ω c > KT , there should be a pronounced change in physical properties that depend on shielding if the system is driven through a high field statistical transition. (It should be noted that the static shielding law of semiclassical and classical models has no dependence on magnetic field in two dimensions, as in three dimensions.) Finally, we find that the zero field two-dimensional Freidel-Kohn “wiggle” static shielding phenomenon is destroyed by the dispersal of the zero field continuum of electron states into the discrete set of Landau-quantized orbitals due to the imposition of the magnetic field.

Nonequilibrium fluctuations and decoherence in nanomechanical devices coupled to the tunnel junction

We analyze the dynamics of a nanomechanical oscillator coupled to an electrical tunnel junction with an arbitrary voltage applied to the junction and arbitrary temperature of electrons in leads. We obtain the explicit expressions for the fluctuations of oscillator position, its damping/decoherence rate, and the current through the structure. It is shown that quantum heating of the oscillator results in nonlinearity of the current-voltage characteristics. The effects of mechanical vacuum fluctuations are also discussed.

BALANCE-EQUATION ANALYSIS OF HOT-CARRIER BLOCH TRANSPORT IN A SUPERLATTICE MINIBAND

A systematic theoretical study of Bloch electron transport in a superlattice miniband driven by a uniform external electric field parallel to the growth axis is carried out, based upon a recent extension of the balance-equation approach to arbitrary energy bands, with a dynamic force-balance equation for the centre of mass (CM), a variable-mass particle embodying the collective motion of the electrons, and a dynamic energy-balance equation. Analyses of both steady-state transport and the transient response to a step and an impulsive electric field are made for various superlattice systems, assuming tight-binding miniband structure and using parameters appropriate for Gamma -valley electrons in GaAs-based quantum-well superlattices at various lattice temperatures.

Phonon-drag effects on thermoelectric power.

We carry out a calculation of the phonon-drag contribution

Aspects of the theory of graphene

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Negative high-frequency differential conductivity in semiconductor superlattices

to the thermoelectric power of bulk semiconductors and quantum well structures using the balance equation transport theory extended to weakly nonuniform systems. Introducing temperature-, wave-vector-, and mode-dependent phonon relaxation times due to phonon-phonon interactions, our formulation can be used not only at low temperatures where the phonon mean free path is determined by boundary scattering, but also at high temperatures. Our analysis of the role of the phonon relaxation times in regard to dependencies on temperature, wave vector, and mode provides results for the linear thermoelectric power

An exact formulation of hyperdynamics simulations

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