Harmonics generation in electron-ion collisions in a short laser pulse

Anomalously high generation efficiency of coherent higher field-harmonics in collisions between {\em oppositely charged particles} in the field of femtosecond lasers is predicted. This is based on rigorous numerical solutions of a quantum kinetic equation for dense laser plasmas which overcomes limitations of previous investigations.Comment: 4 pages, 4 eps-figures include

Quantum kinetic theory of the filamentation instability

The quantum electromagnetic dielectric tensor for a multi species plasma is re-derived from the gauge invariant Wigner-Maxwell system and presented under a form very similar to the classical one. The resulting expression is then applied to a quantum kinetic theory of the electromagnetic filamentation instability. Comparison is made with the quantum fluid theory including a Bohm pressure term, and with the cold classical plasma result. A number of analytical expressions are derived for the cutoff wave vector, the largest growth rate and the most unstable wave vector

Quantum Well Based on Graphene and Narrow-Gap Semiconductors

We consider the energy spectrum of the planar quantum well which consisted of two ribbons of narrow-gap semiconductors and a graphene ribbon between ones. It is shown that the gapless mode appears only in case of inverted narrow-gap semiconductors. Spin splitting of the energy spectrum for a nonsymmetric quantum well is calculated taking into account a specificity of graphene. We investigate interface states and optical transitions. It is shown that the optical transitions are possible only with a conservation of a parity.Comment: 13 pages, 2 figures, 1 tabl

Robustness of a local Fermi Liquid against Ferromagnetism and Phase Separation

We study the properties of Fermi Liquids with the microscopic constraint of a local self-energy. In this case the forward scattering sum-rule imposes strong limitations on the Fermi-Liquid parameters, which rule out any Pomeranchek instabilities. For both attractive and repulsive interactions, ferromagnetism and phase separation are suppressed. Superconductivity is possible in an s-wave channel only. We also study the approach to the metal-insulator transition, and find a Wilson ratio approaching 2. This ratio and other properties of Sr_{1-x}La_xTiO_3 are all consistent with the local Fermi Liquid scenario.Comment: 4 pages (twocolumn format), can compile with or without epsf.sty latex style file -- Postscript files: fig1.ps and fig2.p

Comment on ``Damping of energetic gluons and quarks in high-temperature QCD''

Burgess and Marini have recently pointed out that the leading contribution to the damping rate of energetic gluons and quarks in the QCD plasma, given by $\gamma=c g^2\ln(1/g)T$, can be obtained by simple arguments obviating the need of a fully resummed perturbation theory as developed by Braaten and Pisarski. Their calculation confirmed previous results of Braaten and Pisarski, but contradicted those proposed by Lebedev and Smilga. While agreeing with the general considerations made by Burgess and Marini, I correct their actual calculation of the damping rates, which is based on a wrong expression for the static limit of the resummed gluon propagator. The effect of this, however, turns out to be cancelled fortuitously by another mistake, so as to leave all of their conclusions unchanged. I also verify the gauge independence of the results, which in the corrected calculation arises in a less obvious manner.Comment: 5 page

Quantum scattering in one dimension

A self-contained discussion of nonrelativistic quantum scattering is presented in the case of central potentials in one space dimension, which will facilitate the understanding of the more complex scattering theory in two and three dimensions. The present discussion illustrates in a simple way the concept of partial-wave decomposition, phase shift, optical theorem and effective-range expansion.Comment: 8 page

Kramers-Kronig Relations For The Dielectric Function And The Static Conductivity Of Coulomb Systems

The mutual influence of singularities of the dielectric permittivity e(q,w) in a Coulomb system in two limiting cases w tends to zero, q tends to zero, and opposite q tends to zero, w tends to zero is established. It is shown that the dielectric permittivity e(q,w) satisfies the Kramers-Kronig relations, which possesses the singularity due to a finite value of the static conductivity. This singularity is associated with the long "tails" of the time correlation functions.Comment: 9 pages, 0 figure

Linear theory of nonlocal transport in a magnetized plasma

A system of nonlocal electron-transport equations for small perturbations in a magnetized plasma is derived using the systematic closure procedure of V. Yu. Bychenkov et al., Phys. Rev. Lett. 75, 4405 (1995). Solution to the linearized kinetic equation with a Landau collision operator is obtained in the diffusive approximation. The Fourier components of the longitudinal, oblique, and transversal electron fluxes are found in an explicit form for quasistatic conditions in terms of the generalized forces: the gradients of density and temperature, and the electric field. The full set of nonlocal transport coefficients is given and discussed. Nonlocality of transport enhances electron fluxes across magnetic field above the values given by strongly collisional local theory. Dispersion and damping of magnetohydrodynamic waves in weakly collisional plasmas is discussed. Nonlocal transport theory is applied to the problem of temperature relaxation across the magnetic field in a laser hot spot.Comment: 27 pages, 13 figure

Transient optical response of ultrafast nonequilibrium excited metals: Effects of electron-electron contribution to collisional absorption

Approaching energy coupling in laser-irradiated metals, we point out the role of electron-electron collision as an efficient control factor for ultrafast optical absorption. The high degree of laser-induced electron-ion nonequilibrium drives a complex absorption pattern with consequences on the transient optical properties. Consequently, high electronic temperatures determine largely the collision frequency and establish a transition between absorptive regimes in solid and plasma phases. In particular, taking into account umklapp electron-electron collisions, we performed hydrodynamic simulations of the laser-matter interaction to calculate laser energy deposition during the electron-ion nonequilibrium stage and subsequent matter transformation phases. We observe strong correlations between optical and thermodynamic properties according to the experimental situations. A suitable connection between solid and plasma regimes is chosen in accordance with models that describe the behavior in extreme, asymptotic regimes. The proposed approach describes as well situations encountered in pump-probe types of experiments, where the state of matter is probed after initial excitation. Comparison with experimental measurements shows simulation results which are sufficiently accurate to interpret the observed material behavior. A numerical probe is proposed to analyze the transient optical properties of matter exposed to ultrashort pulsed laser irradiation at moderate and high intensities. Various thermodynamic states are assigned to the observed optical variation. Qualitative indications of the amount of energy coupled in the irradiated targets are obtained. Keywords: ultrafast absorption ; umklapp electron-electron collision ; collisional absorption ; laser-matter interactio

Shielding of a moving test charge in a quantum plasma

The linearized potential of a moving test charge in a one-component fully degenerate fermion plasma is studied using the Lindhard dielectric function. The motion is found to greatly enhance the Friedel oscillations behind the charge, especially for velocities larger than a half of the Fermi velocity, in which case the asymptotic behavior of their amplitude changes from 1/r^3 to 1/r^2.5. In the absence of the quantum recoil (tunneling) the potential reduces to a form similar to that in a classical Maxwellian plasma, with a difference being that the plasma oscillations behind the charge at velocities larger than the Fermi velocity are not Landau-damped.Comment: 9 pages, 11 figures. v3: Fixed typo, updated abstrac