  Using the time-dependent non-crossing approximation, we calculate the
transient response of the current through a quantum dot subject to a finite
bias when the dot level is moved suddenly into a regime where the Kondo effect
is present. After an initial small but rapid response, the time-dependent
conductance is a universal function of the temperature, bias, and inverse time,
all expressed in units of the Kondo temperature. Two timescales emerge: the
first is the time to reach a quasi-metastable point where the Kondo resonance
is formed as a broad structure of half-width of the order of the bias; the
second is the longer time required for the narrower split peak structure to
emerge from the previous structure and to become fully formed. The first time
can be measured by the gross rise time of the conductance, which does not
substantially change later while the split peaks are forming. The second time
characterizes the decay rate of the small split Kondo peak (SKP) oscillations
in the conductance, which may provide a method of experimental access to it.
This latter timescale is accessible via linear response from the steady
stateand appears to be related to the scale identified in that manner [A.
Rosch, J. Kroha, and P. Wolfle, Phys. Rev. Lett. 87, 156802 (2001)].
