Voltage and temperature limits for the operation of a quantum dot ratchet

Open quantum dots without spatial inversion symmetry can partially rectify a small AC voltage because of the asymmetric effect of an electric field on the electron interference inside the dot. Quantum dots can therefore be vi ewed as ratchets, that is devices in which directed particle flow is induce d by non-equilibrium fluctuations, in the absence of (time-averaged) extern al net forces or gradients. Here we discuss thermal energy averaging and ph ase breaking as the parameters that limit the voltage- and temperature rang e where quantum dot ratchets can operate. (C) 1999 Elsevier Science B.V. Al l rights reserved.