AC Kondo effect in quantum dots

Correlation effects in the transport properties of confined electrons coupl ed by quantum-mechanical tunneling to delocalized electrons in the leads - quantum dots - are discussed in the presence of arbitrary intense ac potent ials. Using a time dependent Anderson model we propose a consistent procedu re that, for the first time, allows one to study the full range of paramete rs (from Kondo physics to Coulomb blockade). Our method takes care of charg e conservation by means of a generalized Friedel-Langreth sum rule. We anal yze 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 val ues of the external field is discussed. (C) 1998 Elsevier Science B.V. All rights reserved.