Effect Of Charge Fluctuations Research Articles

Bohm criterion in a dusty plasma with nonextensive electrons and cold ions

The Bohm criterion in a dusty plasma containing nonextensively distributed electrons and cold ions is investigated within the framework of probe model including the effects of dust charge fluctuation. It is shown that the critical Mach number upshifts with the decrease of electron nonextensive parameter (qe) and the increase of the ion-to-electron number density ratio (Rn) when the effects of dust charge fluctuation are out of consideration. Once the effects of dust charge fluctuation are included, with the increase of Rn, the critical Mach number increases first, then decreases. The slop of the critical Mach number curves in the region Rn≫1 for qe>1 becomes more gradual than that for qe<1. When critical Mach number is defined with respect to modified ion acoustic wave speed, it should be larger than unity in the case free of dust charge fluctuation. Whereas when Rn≫1, it may be smaller than unity due to the effect of dust charge fluctuation.

The Effects of Inhomogeneity and Adiabatic Dusty Charge Fluctuation on Solitary Waves

Using the perturbation method, the modified variable coefficient Kadomtsev-Petviashvili (MKP) equation governing nonlinear dust acoustic solitary waves is for the first time derived with the combined effects of adiabatic dust charge fluctuation and higher-order transverse perturbation in inhomogeneous dusty plasmas due to the spatial gradients of dust charge and plasma densities. The MKP equation is reduced to the standard Kadomtsev-Petviashvili (KP) equation. The numerical results show that inhomogeneity has strong influence on the nonlinear properties of dust acoustic solitary waves.

Decoherence of Majorana qubits by noisy gates

We propose and study a realistic model for the decoherence of topological qubits, based on Majorana fermions in one-dimensional topological superconductors. The source of decoherence is the fluctuating charge on a capacitively coupled gate, modeled by noninteracting electrons. In this context, we clarify the role of quantum fluctuations and thermal fluctuations and find that quantum fluctuations do not lead to decoherence, while thermal fluctuations do. We explicitly calculate decay times due to thermal noise and give conditions for the gap size in the topological superconductor and the gate temperature. Based on this result, we provide simple rules for gate geometries and materials optimized for reducing the negative effect of thermal charge fluctuations on the gate.

Debye shielding in a dusty plasma with nonextensively distributed electrons and ions

The phenomenon of Debye shielding in dusty plasmas is investigated within the framework of nonextensively distributed electrons and ions. The effects of dust grain charge fluctuation are considered. It shows that the increase of the nonextensive parameters of electrons and ions will lead to the decrease of the shielding distance and it is due to that the effective temperature of nonextensively distributed particles drops with the increase of nonextensive parameters. There is a rather interesting result that the Debye shielding effects may vanish in a certain condition when the fluctuation of the dust grain charges is taken into account.

Shot-Noise-Induced Failure in Nanoscale Flip-Flops—Part I: Numerical Framework

As CMOS technology continues the path of miniaturization, noise-induced fluctuations raise heightened reliability concerns. In previous work, an analytical framework based on Markov queueing theory and Poisson shot noise was presented to model the probabilistic behavior of a CMOS flip-flop operated in the subthreshold regime. In this paper, this model is extended to also account for the above-threshold shot noise, where the noise distribution is no longer Poissonian. The formulas for the time-dependent charging and discharging of node capacitors of a four-transistor flip-flop are derived for different regimes of operation characterized by distinct Fano factors. The statistics of electron arrival and departure at node capacitors is incorporated in an algebraic representation based on Markov queueing theory to map the effects of charge fluctuations on the logic stability of a flip-flop. This framework is used in Part II of this work to investigate failure in time for end-of-roadmap CMOS at the 10-nm gate-length scale.

Head-on collision of dust acoustic solitary waves with variable dust charge and two temperature ions in an unmagnetized plasma

The head-on collision of dust acoustic solitary waves (DASWs) in an unmagnetized dusty plasma with single electrons, two-temperature ions, variable dust charge is investigated using the extended Poincare-Lighthill-Kuo (PLK) method. The effects of the dust charge fluctuation and two temperature ion are studied. It is found that the dust charge fluctuation and two temperature ion have the significant role on the phase shift.

The effect of dust size distribution and dust charge fluctuation on dust acoustic solitary waves in a magnetized dusty plasma

Dust acoustic solitary waves in a magnetized dusty plasma are studied taking into account the effect of dust size and dust charge variations. Using the analytical and numerical results the influence of different plasma parameters on dust acoustic solitary waves are examined. It is observed that the dust size distribution and dust charge variation have significant contributions on the characteristics of dust acoustic solitary waves.

Cylindrical and spherical dust-electron-acoustic shock waves due to dust charge fluctuation

Cylindrical and spherical dust-electron-acoustic (DEA) shock waves propagating in a dusty plasma (containing cold inertial electrons, hot Maxwellian electrons, stationary and streaming ions, and charge fluctuating stationary dust) are theoretically investigated by reductive perturbation method. It is shown that the effect of the dust charge fluctuation introduces some new features in the nonlinear propagation of the DEA waves, particularly the dust charge fluctuation provides a source of dissipation, and is responsible for the formation of the DEA shock structures. It is also found that the basic features of the DEA nonlinear structures are significantly modified by the non-planar (viz. cylindrical and spherical) geometry, and that the height of the cylindrical DEA shock structures are larger than that of the planar DEA shock structures, but smaller than that of the spherical ones. The implications of these results in laboratory dusty plasmas are briefly discussed.

Distortion of an amplitude modulated electromagnetic signal with time-dependent dust charging

AbstractA large amplitude modulated Gaussian electromagnetic beam propagating in a dusty plasma with dust charge fluctuations has been studied. The electrons are heated non-uniformly by the electromagnetic beam. For non-steady state, we obtain nonlinear current density in the presence of dust grains. This expression has been used to study the non-stationary self-focusing and resulting self-distortion of the amplitude modulated electromagnetic beam. It has been observed that the dust charge fluctuation increases the self-focusing of electromagnetic beam. It is also found that the effect of dust charge fluctuations is significant on the modulation index.

Charge density and bending rigidity of a rodlike polyelectrolyte: Effects of multivalent counterions

We study line charge density and bending persistence length of a semiflexible polyelectrolyte rod typified by DNA in a z:1 electrolyte with or without pre-existing 1:1 salt. We use a wormlike chain model, where the effective Hamiltonian incorporates bending energy, as well as where the Coulomb interaction between charged segments is screened and mediated by the ions in the solution. By analytically evaluating the free energy associated with the contour undulation and charge density fluctuation affected by the adsorbed ions, we find renormalized mean line-charge-density and persistence length. Multivalent counterions bind to the polyelectrolyte more readily than monovalent counterions, due to electrostatic attraction dominant over the entropy. Also, our results show that at physiological conditions the electrostatic interaction gives no appreciable change on the persistence length from its bare value, against the implications of earlier studies. This is because the mean-field and charge fluctuation effects largely cancel each other in the rodlike conformation.

Effects of Nonthermal Ions on Dust-Ion-Acoustic Shock Waves in a Dusty Electronegative Plasma

The nonlinear propagation of dust-ion-acoustic (DIA) waves in a dusty electronegative plasma (consisting of inertialess electrons, nonthermal positive ions, inertial negative ions, and extremely massive charge fluctuating dust) has been investigated by employing the reductive perturbation technique. It has been shown that the effects of nonthermal ions and dust charge fluctuation (associated with Maxwellian electrons and nonthermal positive ions) have significantly modified the basic features of nonlinear DIA waves. The results of this paper would be useful in understanding the basic nonlinear feature of DIA wave propagation in laboratory and space dusty electronegative plasmas.

On the influence of nonlocal molecular vibrations and charge transfer on the spectra of aggregated push–pull chromophores

Through their fluorescence spectrum, aggregates of push-pull chromophores are good reporters of their microenvironment temperature and polarity. The understanding of the fluorescence and charge-separation dynamics in arrays composed of this type of species is consequently of considerable interest. In this article, we study the effect of charge fluctuations induced by molecular nonlocal vibrations on the electronic coupling between a pair of linear push-pull chromophores, for side-to-side or head-to-tail orientations, using a valence-bond charge-transfer (VB-CT) model and the Redfield equation. The results show that the exciton-vibrational dynamics along the bond length alternation coordinate can significantly modify the inter-molecular electronic coupling, which determines the fluorescence spectral band redshift due to aggregation. Numerical results for the electronic and exciton-vibrational contributions to the Coulombic coupling between two of these chromophores are obtained using experimentally based parameters for polyene linker species. The exciton-vibrational contribution is significant relative to the electronic contribution at room temperature in some ranges of the energy gap between the VB and CT states, and it is more important for the side-to-side than for the head-to-tail configuration. Our calculations also show that, even without including solvation effects, the spectral band associated with an S(0) → S(1) transition is redshifted with increasing temperature.

Efficient controlled-phase gate for single-spin qubits in quantum dots

Two-qubit interactions are at the heart of quantum information processing. For single-spin qubits in semiconductor quantum dots, the exchange gate has always been considered the natural two-qubit gate. The recent integration of magnetic field or g-factor gradients in coupled quantum dot systems allows for a one-step, robust realization of the controlled phase (C-Phase) gate instead. We analyze the C-Phase gate durations and fidelities that can be obtained under realistic conditions, including the effects of charge and nuclear field fluctuations, and find gate error probabilities of below 10-4, possibly allowing fault-tolerant quantum computation.

The 3+1 dimensional Kadomtsev–Petviashvili Burgers' equation in non-uniform dusty plasmas

Using the perturbation method, the 3+1 dimensional modified variable coefficient Kadomtsev–Petviashvili (MKP) Burgers' equation governing nonlinear dust acoustic shock waves is derived with the combined effects of non-adiabatic dust charge fluctuation, higher-order transverse perturbation and the non-thermally distributed ions in inhomogeneous dusty plasmas due to spatial gradients of dust charge and plasma densities for the first time. The MKP Burgers' equation is reduced to the standard variable coefficient Kadomtsev–Petviashvili (KP) Burgers' equation. A particular solution of this KP Burgers' equation is also obtained. It is shown that the dust acoustic shock waves can exist in the KP Burgers' equation.

Conformations of semiflexible charged chains: An extended bundle versus repulsive coils

We consider two interacting semiflexible charged chains of length L(c) under shape fluctuations, where the interplay of electric and mechanical properties is found to yield rigidity-sensitive charge modulation and interdistance-dependent persistence length ℓ(p). The resulting conformation is characterized by equilibrium force between the chains and their fractal dimensions. It turns out that ℓ(p) and L(c) emerge as critical factors to determine the force nature as well as chain shapes. We show that conformational fluctuations cause the repulsion of nonsteric origin, and its competition with charge fluctuation effects yields the interchain force modulated by the length scales and counterion valence. As a result, it is predicted that flexible short chains can be more strongly repulsive than rigid long chains, although they carry smaller amount of net charges.

Evolution of ion-acoustic solitary waves in Maxwellian dusty plasmas

The nonlinear wave phenomena in the vicinity of Korteweg–de Vries (KdV) equation have been derived to study the salient features of solitons in a complex plasma consisting of Maxwellian electrons, ions, and cold dust with the effect of dust charge fluctuation. The reductive perturbation method has been applied to the dynamical system causeway and the derived KdV equation predicts different natures of solitons in complex plasma. The dynamics of the soliton propagation in the considered plasma constituents in ionospheric auroral regions exhibits rarefactive solitons, which is an interesting feature. The dust charge fluctuation by the increasing impact of electrons leads the nonlinear effect to be tending to zero. Because of which, the formation of a narrow solitary wave packet with the generation of high energy becomes possible and results in the phenomena of soliton radiation. In order to probe this further, we derive a modified KdV equation to study soliton propagation which, in turn, indicates the possibility of the shock formation in solitary waves.

The effect of dust charge fluctuations on collisional drift waves in a magnetized plasma cylinder

The nonlinear coupling between collisional drift waves and a lower-hybrid pump wave is studied in a magnetized dusty plasma cylinder. A dispersion relation for the collisional drift wave and growth rate is derived incorporating both pondermotive and Ohmic heating effects. The growth rate and mode frequencies were evaluated based on existing dusty plasma parameters. It is found that the unstable collisional drift mode frequency increases and the growth rate decreases sharply with the relative density of negatively charged dust grains. Moreover, the collisional frequency has no effect on the unstable drift mode frequency. However, the increases in collisional frequency and electron temperature are playing an important role in the damping effect.

The role of dust charging frequency in the linear and nonlinear propagation of dust acoustic waves

The effect of dust charge fluctuation on the existence and propagation of dust acoustic waves in unmagnetized dusty plasma is studied. Dispersion relation for the dust acoustic waves with temporal dust charge fluctuations is calculated based on the reductive perturbation technique. By considering two different limiting cases of the dust charging frequency, it is shown that the dusty plasma system gives rise to linear or nonlinear dust acoustic waves. The well-known collisionless damping of two existing normal modes and one purely damped mode are recovered when the dust charging frequency is comparable to the dust acoustic wave frequency. On the other hand, when the dust charging frequency is considerably higher than the wave frequency, it is then possible to derive a nonlinear Schrödinger type equation with envelope soliton as solution.

The effects of nonadiabatic dust charge variation and ultraviolet irradiation on the modulational instability of dust ion acoustic waves

The effects of nonadiabatic dust charge fluctuation on the nonlinear propagation of the dust ion acoustic (DIA) waves in the dusty plasma with positively charged dust grains have been investigated. By using the reductive perturbation technique, a three-dimensional modified nonlinear Schrödinger equation (mNLSE) governing the nonlinear envelope DIA waves was derived and the approximate solitary wave solution of the mNLSE was also obtained in the weak effect of nonadiabatic dust charge fluctuation limit, which shows that the amplitude of the DIA solitary wave exponentially decreases with time due to the collisionless dissipation caused by the nonadiabatic dust charge variation. The frequency, instability growth rate, and the critical modulational wave number of the small amplitude modulation are all dependent on photoelectron generated by ultraviolet irradiation and time due to the presence of nonadiabatic dust charge variation. The transverse perturbation plays an important role in the modulational instability region.

Dust ion-acoustic solitary and shock waves due to dust charge fluctuation with vortexlike electrons

A rigorous theoretical investigation has been made of the dust ion-acoustic (DIA) solitary and shock waves in an unmagnetized dusty plasma (containing vortexlike electrons, mobile ions, and charge fluctuating static dust) by reductive perturbation method. The effects of dust grain charge fluctuation and vortexlike (trapped) electron are found to modify the properties of the DIA solitary and shock waves significantly. The implications of these results for some space and astrophysical dusty plasma systems, especially planetary ring systems, are briefly mentioned.