A multi-band semiclassical model for surface hopping quantum dynamics

In the paper we derive a semiclassical model for surface hopping allowing quantum dynamical non-adiabatic transition between different potential energy surfaces in which cases the classical Born-Oppenheimer approximation breaks down. The model is derived using the Wigner transform and Weyl quantization, and the central idea is to evolve the entire Wigner matrix rather than just the diagonal entries as was done previously in the adiabatic case. The off-diagonal entries of the Wigner matrix suitably describe the non-adiabatic transition, such as the Berry connection, for avoided crossings. We study the numerical approximation issues of the model, and then conduct numerical experiments to validate the model.Comment: 29 pages, 10 figure

Semiclassical Vlasov and fluid models for an electron gas with spin effects

We derive a four-component Vlasov equation for a system composed of spin-1/2 fermions (typically electrons). The orbital part of the motion is classical, whereas the spin degrees of freedom are treated in a completely quantum-mechanical way. The corresponding hydrodynamic equations are derived by taking velocity moments of the phase-space distribution function. This hydrodynamic model is closed using a maximum entropy principle in the case of three or four constraints on the fluid moments, both for Maxwell-Boltzmann and Fermi-Dirac statistics.Comment: To appear in the European Physical Journal D, Topical Issue "Theory and Applications of the Vlasov Equation

Hydrodynamic Models with Quantum Corrections

We derive a quantum-corrected hydrodynamic and drift-diffusion model for the out-of-equilibrium particle dynamics in the presence of particle collisions, modeled by a BGK collision term. The quantum mechanical corrections are obtained within the Liouville formalism and are expressed by an effective nonlinear force. The Boltzmann and Fermi-Dirac statistics are included

Changes in leaflet shape and seeds per pod modify crop growth parameters, canopy light environment, and yield components in soybean

Seed number (SN) is the component most strongly associated with yield in soybean. SN depends on pod number (PN) and seeds per pod (SPP). Whereas SPP is a relatively stable component, PN is strongly influenced by environmental and management factors. However, the environmental cues involved in PN regulation are not completely understood. The influence of increasing SPP on other yield components is controversial. Field trials were conducted in two growing seasons using two pairs of lanceolate (L) and ovate (O) near-isogenic lines, sown at low (LD) and high (HD) plant densities to evaluate the effect of leaflet shape on crop growth parameters, canopy red/far-red (R/FR) ratio, their relationships with pod initiation, PN, and yield; and the effect of increasing SPP on PN, SN, and yield. L canopies showed a higher number of pods initiated (PI) than O canopies owing to the increase of PI on branches. No association between PI and crop growth rate during the pod set period was found. PI was negatively associated with leaf area index (LAI) and light interception. In contrast, a positive association between PI and canopy R/FR ratio was found. This latter association was sustained irrespective of whether the LAI was below or above its critical value, providing experimental evidence that R/FR ratio is positively associated with pod initiation in soybean canopies. An increase in SPP produced a direct and steady increase in SN regardless of PN and plant density. A yield increase was observed for the L-LD treatment, which combined the increased SPP of L lines with the highest PN of L-LD canopies. These results have implications for crop management and breeding strategies aimed at increasing the yield potential of soybean.Fil: Bianchi, Julieta Sofia. Universidad Nacional de Rosario. Facultad de Ciencias Agrarias. Departamento de Biologia. Cátedra de Fisiología Vegetal; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Investigaciones en Ciencias Agrarias de Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Agrarias. Instituto de Investigaciones en Ciencias Agrarias de Rosario; ArgentinaFil: Quijano, Alvaro. Universidad Nacional de Rosario. Facultad de Ciencias Agrarias. Departamento de Biologia. Cátedra de Fisiología Vegetal; Argentina. Universidad Nacional de Rosario. Consejo de Investigaciones de la Universidad de Rosario; ArgentinaFil: Gosparini, Carlos Omar. Universidad Nacional de Rosario. Facultad de Ciencias Agrarias. Departamento de Biologia. Cátedra de Fisiología Vegetal; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Investigaciones en Ciencias Agrarias de Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Agrarias. Instituto de Investigaciones en Ciencias Agrarias de Rosario; ArgentinaFil: Morandi, Eligio Natalio. Universidad Nacional de Rosario. Facultad de Ciencias Agrarias. Departamento de Biologia. Cátedra de Fisiología Vegetal; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Investigaciones en Ciencias Agrarias de Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Agrarias. Instituto de Investigaciones en Ciencias Agrarias de Rosario; Argentin

Time-dependent model for diluted magnetic semiconductors including band structure and confinement effects

10 pagesInternational audienceA free-parameter theoretical model is developed in order to study the ultrafast dynamics in confined diluted magnetic semiconductors induced by laser. The hole-spin relaxation process is due to the Elliot-Yafet mechanism, which involves the scattering of the holes on the localized magnetic impurities. The role played by the quantum confinement and the band structure is analyzed. It is shown that the sample thickness and the background hole density strongly influences the phenomenon of demagnetization. Quantitative results are given for III-V ferromagnetic GaMnAs quantum wells of thickness 4 and 6 nm

A multiband envelope function model for quantum transport in a tunneling diode

We present a simple model for electron transport in semiconductor devices that exhibit tunneling between the conduction and valence bands. The model is derived within the usual Bloch-Wannier formalism by a k-expansion, and is formulated in terms of a set of coupled equations for the electron envelope functions. Its connection with other models present in literature is discussed. As an application we consider the case of a Resonant Interband Tunneling Diode, demonstrating the ability of the model to reproduce the expected behaviour of the current as a function of the applied voltageComment: 8 pages, 4 figure

Pseudo-fermion formalism applied to nonequilibrium Kondo-type problems

8 pagesInternational audienceA straightforward limit procedure is developed for evaluating the expectation value of a generic many-particle operator defined in the Abrikosov-Coleman's pseudo fermion formalism. It can be useful for the study of nonequilibrium Kondo-type problems

Quantum-relativistic hydrodynamic model for a spin-polarized electron gas interacting with light

We develop a semirelativistic quantum fluid theory based on the expansion of the Dirac Hamiltonian to second order in 1/c. By making use of the Madelung representation of thewave function, we derive a set of hydrodynamic equations that comprises a continuity equation, an Euler equation for the mean velocity, and an evolution equation for the electron spin density. This hydrodynamic model is then applied to study the dynamics of a dense and weakly relativistic electron plasma. In particular, we investigate the impact of the quantum-relativistic spin effects on the Faraday rotation in a one-dimensional plasma slab irradiated by an x-ray laser source