A recently demonstrated quantum electron pump is discussed within the framework of photon-assisted tunneling. Because of lack of time-reversal symmetry, different results are obtained for the pump current depending on whether or not final-state Pauli blocking factors are used when describing the tunneling process. While in both cases the current depends quadratically on the driving amplitude for moderate pumping, a marked difference is predicted for the temperature dependence. With blocking factors the pump current decreases roughly linearly with temperature until $k_{B}T\approx ħ\omega$ is reached, whereas without them it is unaffected by temperature, indicating that the entire Fermi sea participates in the transport.

• Received 16 February 2000

DOI:https://doi.org/10.1103/PhysRevLett.85.174