Electronic transport through nanostructures, especially the steady-state
transport under time-independent voltage, has attracted much attention
because it plays an essential role in next-generation nanoscale devices.
The time-dependent transport phenomena are also of interest in various
contexts such as transient behaviors and AC response in high-frequency
amplifiers.
In this talk, we present a new numerical formulation based on the
Liouville-von Neumann equation approach to treat the time-dependent
electronic transport through nanostructures suspended between electrodes.
As a simplest application of the numerical formulation, we discuss the
time-dependent transport in atomic contact systems consisting of
[left lead]-[atomic chain]-[right lead]. After switching on the bias voltage,
the current arrives at a steady state with oscillations due to electron
travelling back and forth between an electrode and the atomic chain.
The oscillating period is related to the energy difference between the
Fermi energy of the lead and the molecular levels in the atomic chain.
The relaxation time is mainly determined by the coupling strength between
electrodes and the nanostructure as well as density of states of electrodes.
The details will be discussed in the presentation. |