AC Kondo effect in quantum dots

Correlation effects in the transport properties of confined electrons coupled by quantum-mechanical tunneling to delocalized electrons in the leads - quantum dots - are discussed in the presence of arbitrary intense ac potentials. Using a time dependent Anderson model we propose a consistent procedure that, for the first time, allows one to study the full range of parameters (from Kondo physics to Coulomb blockade). Our method takes care of charge conservation by means of a generalized Friedel-Langreth sum rule. We analyze the ac Kondo problem at zero temperature in a wide range of parameters. The effect of the ac potential on the linear conductance for different values of the external field is discussed. (C) 1998 Elsevier Science B.V. All rights reserved.