The control of nonlinear processes and possible transitions to chaos in
systems of interacting particles is a fundamental physical problem. We propose
a new nonuniform solid-state plasma system, produced by the optical injection
of current in two-dimensional semiconductor structures, where this control can
be achieved. Due to an injected current, the system symmetry is initially
broken. The subsequent nonequilibrium dynamics is governed by the spatially
varying long-range Coulomb forces and electron-hole collisions. As a result,
inhomogeneities in the charge and velocity distributions should develop
rapidly, and lead to previously unexpected experimental consequences. We
suggest that the system eventually evolves into a behavior similar to chaos.Comment: 3 figure
We investigate the charge and spin dynamics of optically injected currents in multiple quantum well structures using a hydrodynamic model. The dynamics is very complex even on time scales of the order of 1 ps due to the interplay of Coulomb forces, electron-hole drag effects, and nonlinearity of the equations of motion. Our analysis is based on a numerical approach employing an expansion of the calculated quantities in a Hermite–Gaussian basis. We calculate the evolution of the density of injected carriers, analyze the pattern of charges after the injection, and extract the parameters that characterize the overall charge displacement in the optical pump-probe and terahertz radiation experiments. While these two parameters would take on the same value if the injected charge distributions moved rigidly, we find that their observed values should be different due to the complex behavior of the carrier motion. The spin flows arising from the spin-dependent skew scattering of electron by holes and corresponding spin density distributions are calculated and analyzed.
We use a hydrodynamic model to describe the relaxation of optically injected currents in quantum wells on a picosecond time scale, numerically solving the continuity and velocity evolution equations with the Hermite-Gaussian functions employed as a basis. The interplay of the long-range Coulomb forces and nonlinearity in the equations of motion leads to rather complex patterns of the calculated charge and current densities. We find that the time dependence of even the first moment of the electron density is sensitive to this complex evolution.
Due to strong absorption of the incident light, the media with high refractive index are considered restrictive for applications in photonic crystals (PhCs). The possibility to resolve this problem by optical saturation effectively minimizing the absorption of the PhC medium is discussed. Such approach might be promising for the significant broadening of the photonic band-gap.
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