1,352,169 research outputs found
Arrival time distribution for a driven system containing quenched dichotomous disorder
We study the arrival time distribution of overdamped particles driven by a
constant force in a piecewise linear random potential which generates the
dichotomous random force. Our approach is based on the path integral
representation of the probability density of the arrival time. We explicitly
calculate the path integral for a special case of dichotomous disorder and use
the corresponding characteristic function to derive prominent properties of the
arrival time probability density. Specifically, we establish the scaling
properties of the central moments, analyze the behavior of the probability
density for short, long, and intermediate distances. In order to quantify the
deviation of the arrival time distribution from a Gaussian shape, we evaluate
the skewness and the kurtosis.Comment: 18 pages, 5 figure
Real-Time Propagation TDDFT and Density Analysis for Exciton Couplings Calculations in Large Systems
Photo-active systems are characterized by their capacity of absorbing light
energy and transforming it. Usually, more than one chromophore is involved in
the light absorption and excitation transport processes in complex systems.
Linear-Response Time-Dependent Density Functional (LR-TDDFT) is commonly used
to identify excitation energies and transition properties by solving well-known
Casida's equation for single molecules. However, this methodology is not useful
in practice when dealing with multichromophore systems. In this work, we extend
our local density decomposition method that enables to disentangle individual
contributions into the absorption spectrum to computation of exciton dynamic
properties, such as exciton coupling parameters. We derive an analytical
expression for the transition density from Real-Time Propagation TDDFT
(P-TDDFT) based on Linear Response theorems. We demonstrate the validity of our
method to determine transition dipole moments, transition densities and exciton
coupling for systems of increasing complexity. We start from the isolated
benzaldehyde molecule, perform a distance analysis for -stacked dimers and
finally map the exciton coupling for a 14 benzaldehyde cluster.Comment: 32 pages, 8 figures; added references in introductions, typos fixe
Time-Dependent Magnons from First Principles
We propose an efficient and non-perturbative scheme to compute magnetic excitations for extended systems employing the framework of time-dependent density functional theory. Within our approach, we drive the system out of equilibrium using an ultrashort magnetic kick perpendicular to the ground-state magnetization of the material. The dynamical properties of the system are obtained by propagating the time-dependent Kohn–Sham equations in real time, and the analysis of the time-dependent magnetization reveals the transverse magnetic excitation spectrum of the magnet. We illustrate the performance of the method by computing the magnetization dynamics, obtained from a real-time propagation, for iron, cobalt, and nickel and compare them to known results obtained using the linear-response formulation of time-dependent density functional theory. Moreover, we point out that our time-dependent approach is not limited to the linear-response regime, and we present the first results for nonlinear magnetic excitations from first principles in iron
Linear scaling calculation of a n-type GaAs quantum dot
A linear scale method for calculating electronic properties of large and
complex systems is introduced within a local density approximation. The method
is based on the Chebyshev polynomial expansion and the time-dependent method,
which is tested in calculating the electronic structure of a model n-type GaAs
quantum dot.Comment: 5 pages, 3 figure
Time-dependent density functional theory beyond the adiabatic local density approximation
In the current density functional theory of linear and nonlinear
time-dependent phenomena, the treatment of exchange and correlation beyond the
level of the adiabatic local density approximation is shown to lead to the
appearance of viscoelastic stresses in the electron fluid. Complex and
frequency-dependent viscosity/elasticity coefficients are microscopically
derived and expressed in terms of properties of the homogeneous electron gas.
As a first consequence of this formalism, we provide an explicit formula for
the linewidths of collective excitations in electronic systems.Comment: RevTeX, 4 page
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