  We present a comprehensive theoretical investigation on the dynamic
electronic response of a noninteracting quantum dot system to various forms of
time-dependent voltage applied to the single contact lead. Numerical
simulations are carried out by implementing a recently developed hierarchical
equations of motion formalism [J. Chem. Phys. 128, 234703 (2008)], which is
formally exact for a fermionic system interacting with grand canonical
fermionic reservoirs, in the presence of arbitrary time-dependent applied
chemical potentials. The dynamical characteristics of the transient transport
current evaluated in both linear and nonlinear response regimes are analyzed,
and the equivalent classic circuit corresponding to the coupled dot-lead system
is also discussed.
