How long does it take for the Kondo effect to develop?

The time development of the Kondo effect is theoretically investigated by s tudying a quantum dot suddenly shifted into the Kondo regime by a change of voltage on a nearby gate. Using time-dependent versions of both the Anders on and Kondo Hamiltonians, it is shown that after a time t following the vo ltage shift, the form of the Kondo resonance matches the time-independent r esonance at an effective temperature T-eff = T/tanh(pi Tt/2). Relevance of the buildup of the Kondo resonance to the transport current through a quant um dot is demonstrated.