196 research outputs found
Second-order post-Hartree-Fock perturbation theory for the electron current
Based on the super-fermion representation of quantum kinetic equations we
develop nonequilibrium, post-Hartree-Fock many-body perturbation theory for the
current through a region of interacting electrons. We apply the theory to out
of equilibrium Anderson model and discuss practical implementation of the
approach. Our calculations show that nonequilibrium electronic correlations may
produce significant quantitative and qualitative corrections to mean-field
electronic transport properties. We find that the nonequilibrium leads to
enhancement of electronic correlations
Stability analysis of multiple nonequilibrium fixed points in self-consistent electron transport calculations
We present a method to perform stability analysis of nonequilibrium fixed
points appearing in self-consistent electron transport calculations. The
nonequilibrium fixed points are given by the self-consistent solution of
stationary, nonlinear kinetic equation for single-particle density matrix. We
obtain the stability matrix by linearizing the kinetic equation around the
fixed points and analyze the real part of its spectrum to assess the asymptotic
time behavior of the fixed points. We derive expressions for the stability
matrices within Hartree-Fock and linear response adiabatic time-dependent
density functional theory. The stability analysis of multiple fixed points is
performed within the nonequilibrium Hartree-Fock approximation for the electron
transport through a molecule with a spin-degenerate single level with local
Coulomb interaction
Kramers problem for nonequilibrium current-induced chemical reactions
We discuss the use of tunneling electron current to control and catalyze
chemical reactions. Assuming the separation of time scales for electronic and
nuclear dynamics we employ the Langevin equation for the reaction coordinate.
The Langevin equation contains current-induced forces and is used to define
nonequilibrium, effective potential energy surface for current-carrying
molecular systems. The current-induced forces are computed via Keldysh
nonequilibrium Green's functions. Once the nonequilibrium, current-depended
potential energy surface is defined, the chemical reaction is modeled as an
escape of a Brownian particle from the potential well. We demonstrate that the
barrier between the reactant and the product states can be controlled by the
bias voltage. When the molecule is asymmetrically coupled to the electrodes,
the reaction can be catalyzed or stopped depending on the polarity of the
tunneling current.Comment: 4 pages, 2 figure
Neutrino absorption by hot nuclei in supernova environments
Using the thermal quasiparticle random phase approximation, we study the
process of neutrino and antineutrino capture on hot nuclei in supernova
environments. For the sample nuclei Fe and Ge we perform a
detailed analysis of thermal effects on the strength distribution of allowed
Gamow-Teller transitions which dominate low-energy charged-current neutrino
reactions. The finite temperature cross sections are calculated taking into
account the contributions of both allowed and forbidden transitions. The
enhancement of the low-energy cross sections is explained by considering
thermal effects on the GT strength. For Fe we compare the
calculated finite-temperature cross sections with those obtained from
large-scale shell-model calculations.Comment: Minor revisions according to referee's recomendation
Inelastic neutrino scattering off hot nuclei in supernova environments
We study inelastic neutrino scattering off hot nuclei for temperatures
relevant under supernova conditions. The method we use is based on the
quasiparticle random phase approximation extended to finite temperatures within
the thermo field dynamics (TQRPA). The method allows a transparent treatment of
upward and downward transitions in hot nuclei, avoiding the application of
Brink's hypothesis. For the sample nuclei Fe and Ge we perform a
detailed analysis of thermal effects on the strength distributions of allowed
Gamow-Teller (GT) transitions which dominate the scattering process at low
neutrino energies. For Fe and Ge the finite temperature
cross-sections are calculated by taking into account the contribution of
allowed and forbidden transitions. The observed enhancement of the
cross-section at low neutrino energies is explained by considering thermal
effects on the GT strength. For Fe we compare the calculated
cross-sections to those obtained earlier from a hybrid approach that combines
large-scale shell-model and RPA calculations.Comment: 12 pages, 9 figure
Thermal QRPA with Skyrme interactions and supernova neutral-current neutrino-nucleus reactions
The Thermal Quasiparticle Random-Phase Approximation is combined with the
Skyrme energy density functional method (Skyrme-TQRPA) to study the response of
a hot nucleus to an external perturbation. For the sample nuclei, Fe and
Ge, the Skyrme-TQRPA is applied to analyze thermal effects on the
strength function of charge-neutral Gamow-Teller transitions which dominate
neutrino-nucleus reactions at ~MeV. For the relevant
supernova temperatures we calculate the cross sections for inelastic neutrino
scattering. We also apply the method to examine the rate of
neutrino-antineutrino pair emission by hot nuclei. The cross sections and rates
are compared with those obtained earlier from the TQRPA calculations based on
the phenomenological Quasiparticle-Phonon Model Hamiltonian. For inelastic
neutrino scattering on Fe we also compare the Skyrme-TQRPA results to
those obtained earlier from a hybrid approach that combines shell-model and RPA
calculations.Comment: Minor revisions according to referee's recomendation
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