We have applied time-dependent density-functional theory (TDDFT) to
investigate the electron flow through various two-dimensional (2D)
structures. In our approach the finite 2D computing region is divided into
two parts: (i) the time-independent quantum-dot reservoir initially filled
with electrons and (ii) a time-dependent channel which contains a device
potential (scattering center) of a desired shape at the center. First, the
static Kohn-Sham equation is solved for the electrons in the reservoir.
Thereafter, the ground-state Kohn-Sham wave functions are used as initial
states and are propagated on the potential landscape smoothly connected to
the reservoir, so that the electrons can enter the channel freely at times
t > 0. The charge flow through the channel and device region is driven
solely by the wave-packet dispersion and electron-electron repulsion, so
that no external bias is needed. We monitor the current density at
different points in space until the unrealistic back-scattering effects
due to the finite simulation area distort the description of a real
infinite system. In several test cases, however, our approach leads to
excellent agreement with the nonequilibrium Green's function method.
Until now, we have applied our TDDFT approach in the level of adiabatic
local-density approximation to simulate charge transport through quantum
rings and quantum-point contacts in static, uniform magnetic fields. In
particular, we have examined the effects of electron-electron interactions
on the Aharonov-Bohm oscillations in the conductance of realistic quantum
rings. |