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Density functional theory and Material Science (2007)

Organizers: Jürgen Hafner (TU Vienna), Georg Kresse (U. Vienna), Raimund Podloucky (U. Vienna), Peter Mohn (TU Vienna)

Talks


Räsänen, Esa WPI Seminar room C714, Nordbergstr. 15 Mon, 3. Dec 07, 17:30
Real-space-time quantum transport in finite systems
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.
  • Thematic program: Density functional theory and Material Science (2007)

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