The Experts below are selected from a list of 291 Experts worldwide ranked by ideXlab platform
Nelson Yokomizo - One of the best experts on this subject based on the ideXlab platform.
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radiation from electrons in graphene in Strong Electric Field
Annals of Physics, 2014Co-Authors: Nelson YokomizoAbstract:Abstract We study the interaction of electrons in graphene with the quantized electromagnetic Field in the presence of an applied uniform Electric Field using the Dirac model of graphene. Electronic states are represented by exact solutions of the Dirac equation in the Electric background, and amplitudes of first-order Feynman diagrams describing the interaction with the photon Field are calculated for massive Dirac particles in both valleys. Photon emission probabilities from a single electron and from a many-electron system at the charge neutrality point are derived, including the angular and frequency dependence, and several limiting cases are analyzed. The pattern of photon emission at the Dirac point in a Strong Field is determined by an interplay between the nonperturbative creation of electron–hole pairs and spontaneous emission, allowing for the possibility of observing the Schwinger effect in measurements of the radiation emitted by pristine graphene under DC voltage.
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dirac fermions in Strong Electric Field and quantum transport in graphene
Physical Review D, 2012Co-Authors: S P Gavrilov, D M Gitman, Nelson YokomizoAbstract:Our previous results on the nonperturbative calculations of the mean current and of the energy-momentum tensor in QED with the T-constant Electric Field are generalized to arbitrary dimensions. The renormalized mean values are found; the vacuum polarization and particle creation contributions to these mean values are isolated in the large T-limit, the vacuum polarization contributions being related to the one-loop effective Euler-Heisenberg Lagrangian. Peculiarities in odd dimensions are considered in detail. We adapt general results obtained in 2+1 dimensions to the conditions which are realized in the Dirac model for graphene. We study the quantum electronic and energy transport in the graphene at low carrier density and low temperatures when quantum interference effects are important. Our description of the quantum transport in the graphene is based on the so-called generalized Furry picture in QED where the Strong external Field is taken into account nonperturbatively; this approach is not restricted to a semiclassical approximation for carriers and does not use any statistical assumtions inherent in the Boltzmann transport theory. In addition, we consider the evolution of the mean electromagnetic Field in the graphene, taking into account the backreaction of the matter Field to the applied external Field. We find solutions of the corresponding Dirac-Maxwell set of equations and with their help we calculate the effective mean electromagnetic Field and effective mean values of the current and the energy-momentum tensor. The nonlinear and linear I-V characteristics experimentally observed in both low and high mobility graphene samples is quite well explained in the framework of the proposed approach, their peculiarities being essentially due to the carrier creation from the vacuum by the applied Electric Field.
Bai Mindi - One of the best experts on this subject based on the ideXlab platform.
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synthesis of ammonia in a Strong Electric Field discharge at ambient pressure
Plasma Chemistry and Plasma Processing, 2000Co-Authors: Bai Mingdong, Bai Xiyao, Zhang Zhitao, Bai MindiAbstract:The plasma synthesis of ammonia has been studied in a nitrogen–hydrogenplasma using a Strong Electric Field discharge at ambient pressure andtemperature. With this method, N2 and H2 molecules are ionized anddissociated and a large number of free atoms, ions, and radicals areformed in a nonequilibrium plasma after inelastic collisions. The finalproduct was mainly ammonia, including a small amount of hydrazine. WhenMgO powder, used as a catalyst, was smeared on the surface of the electrodeplates, the yields of ammonia increased about 1.54–1.75 times andreached 5000 ppm (0.5% v/v). In this way, plasma synthesis of ammonia atambient pressure is realized and a new method is provided for inorganicsynthesis, which consumes little energy and simplifies the process.
Emil Mottola - One of the best experts on this subject based on the ideXlab platform.
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fermion pair production in a Strong Electric Field
Physical Review D, 1992Co-Authors: Yuval Kluger, J.m. Eisenberg, Benjamin Svetitsky, Fred Cooper, Emil MottolaAbstract:The initial-value problem for the quantum back reaction in spinor QED is formulated and solved in the semiclassical mean-Field approximation for a homogeneous but time-dependent Electric Field $E(t)$. We apply the method of adiabatic regularization to the Dirac equation in order to renormalize the expectation value of the current and derive a finite coupled set of ordinary differential equations for the time evolution of the system. We solve this system in 1+1 dimensions numerically and compare the solution to a simple model based on a relativistic Boltzmann-Vlasov equation, with a particle production source term inferred from the Schwinger particle creation rate and a Pauliblocking factor. This model reproduces very well the time behavior of the Electric Field and the creation rate of ${e}^{+}{e}^{\ensuremath{-}}$ pairs of the semiclassical calculation.
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Pair production in a Strong Electric Field.
Physical review letters, 1991Co-Authors: Yuval Kluger, J.m. Eisenberg, Benjamin Svetitsky, Fred Cooper, Emil MottolaAbstract:We investigate the mechanism of pair creation in scalar QED from spatially homogeneous Strong Electric Fields in 1+1 dimensions. Solution of the semiclassical Field equations shows particle creation followed by plasma oscillations. We compare our results with a model based on a relativistic Boltzmann-Vlasov equation with a pair-creation source term related to the Schwinger mechanism. The time evolution of the Electric Field and the current obtained from the Boltzmann-Vlasov model is surprisingly similar to that found in the semiclassical calculation.
Bai Mingdong - One of the best experts on this subject based on the ideXlab platform.
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synthesis of ammonia in a Strong Electric Field discharge at ambient pressure
Plasma Chemistry and Plasma Processing, 2000Co-Authors: Bai Mingdong, Bai Xiyao, Zhang Zhitao, Bai MindiAbstract:The plasma synthesis of ammonia has been studied in a nitrogen–hydrogenplasma using a Strong Electric Field discharge at ambient pressure andtemperature. With this method, N2 and H2 molecules are ionized anddissociated and a large number of free atoms, ions, and radicals areformed in a nonequilibrium plasma after inelastic collisions. The finalproduct was mainly ammonia, including a small amount of hydrazine. WhenMgO powder, used as a catalyst, was smeared on the surface of the electrodeplates, the yields of ammonia increased about 1.54–1.75 times andreached 5000 ppm (0.5% v/v). In this way, plasma synthesis of ammonia atambient pressure is realized and a new method is provided for inorganicsynthesis, which consumes little energy and simplifies the process.
Mark I Stockman - One of the best experts on this subject based on the ideXlab platform.
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wannier stark states of graphene in Strong Electric Field
Physical Review B, 2014Co-Authors: Hamed Koochaki Kelardeh, Vadym Apalkov, Mark I StockmanAbstract:We find theoretically the energy spectrum of a graphene monolayer in a Strong constant Electric Field using a tight-binding model. Within a single band, we find quantized equidistant energy levels (Wannier-Stark ladder), separated by the Bloch frequency. Singular interband coupling results in mixing of the states of different bands and anticrossing of corresponding levels, which is described analytically near Dirac points and is related to the Pancharatnam-Berry phase. The rate of interband tunneling, which is proportional to the anticrossing gaps in the spectrum, is only inversely proportional to the tunneling distance, in a sharp contrast to conventional solids where this dependence is exponential. This singularity will have major consequences for graphene behavior in Strong ultrafast optical Fields, in particular, leading to nonadiabaticity of electron excitation dynamics.
