Transport of matter and energy in a mesoscopic thermo-hydrodynamic approach

We derive a thermo-hydrodynamic theory for particles and energy flow, based on a nonequilibrium grand-canonical ensemble formalism. The time-dependent kinetic coefficients are explicitly given in terms of microscopic mechanical quantities. The time evolution equations describing the coupled flow of energy and particles are derived. The second-rank tensorial fluxes of current of energy and particles present in the nonequilibrium ensemble are nondiagonal. We obtain a generalized Fick's Law, which presents the effect of the energy flow on the particle diffusion equation. (C) 2004 American Institute of Physics.120167526753

Markovian kinetic equations in a nonequilibrium statistical ensemble formalism

The nonlinear quantum kinetic theory for many-body systems either near or far from equilibrium that a nonequilibrium ensemble formalism provides is revisited. In this communication we consider an important limit of such transport equations, consisting of the memoryless approximation, which leads to the so-called Markovian kinetic equations. They are derived in Zubarev's approach to the method, and next applied to a particular model of a spin system in interaction with a thermal bath of lattice vibrations. The limitations of the approach, as well as some criticism it has received, are discussed.573B3637364

Spatially indirect excitons in type-II quantum dots

The authors have calculated the electronic structure for type-II InP/GaAs quantum dot systems considering a three-dimensional geometry including the wetting layer and the electron-hole interaction, which is the only responsible for the hole localization. Their results for the InP/GaAs structure show the electron confined inside the dot and the hole in the GaAs layer, partially above and below the dot. The authors propose structures with InGaAs or InGaP layers, where the hole wave function forms a ring around the dot walls. The electron-hole overlap, and therefore, the carrier lifetimes are very sensitive to the structural geometry, which is an important tool for device engineering. (c) 2007 American Institute of Physics.902

Higher-order hydrodynamics: Extended Fick's Law, evolution equation, and Bobylev's instability

A higher-order hydrodynamics for material motion in fluids, under arbitrary nonequilibrium conditions, is constructed. We obtain what is a generalized-to that conditions-Fick-type Law. It includes a representation of Burnett-type contributions of all order, in the form of a continuous-fraction expansion. Also, the equation includes generalized thermodynamic forces. which are characterized and discussed. All kinetic coefficients are given as correlations of microscopic mechanical quantities averaged over the nonequilibrium ensemble, and then are time- and space-dependent as a consequence of accounting for the dissipative processes that are unfolding in the medium. An extended evolution equation for the density of particles is derived, and the conditions when it goes over restricted forms of the type of the telegraphist equation and Fick's diffusion equation are presented. (C) 2002 American Institute of Physics.11641571158

Polarized and resonant Raman spectroscopy on single InAs nanowires

We report polarized Raman scattering and resonant Raman scattering studies on single InAs nanowires.Polarized Raman experiments show that the highest scattering intensity is obtained when both the incident and analyzed light polarizations are perpendicular to the nanowire axis. InAs wurtzite optical modes are observed. The obtained wurtzite modes are consistent with the selection rules and also with the results of calculations using an extended rigid-ion model. Additional resonant Raman scattering experiments reveal a redshifted E1 transition for InAs nanowires compared to the bulk zinc-blende InAs transition due to the dominance of the wurtzite phase in the nanowires. Ab initio calculations of the electronic band structure for wurtzite and zinc-blende InAs phases corroborate the observed values for the E1 transitions

Evolution of dissipative processes via a statistical thermodynamic approach. II. Thermodynamic properties of a fluid of bosons

On the basis of the generalized Mori-Heisenberg-Langevin equations presented in the preceding paper, we derive and analyze the informational-statistical thermodynamic properties of a fluid of bosons away from equilibrium. We derive the informational entropy and its production, proceeding to an analysis of the several contributions to these state functions arising out of the evolution of dissipative processes in the system. (C) 1998 American Institute of Physics.108187580758

Field effect on the impact ionization rate in semiconductors

Impact ionization plays a crucial role for electron transport in semiconductors at high electric fields. We derive appropriate quantum kinetic equations for electron transport in semiconductors within linear response theory. The field-dependent collision integral is evaluated for the process of impact ionization. A known, essentially analytical result is reproduced within the parabolic band approximation [W. Quade , Phys. Rev. B 50, 7398 (1994)]. Based on the numerical results for zero field strengths but realistic band structures, a fit formula is proposed for the respective field-dependent impact ionization rate. Explicit results are given for GaAs, Si, GaN, ZnS, and SrS. (C) 2000 American Institute of Physics. [S0021-8979(00)03002-4].87278178