Pumps operating at the boundary between the classical and the quantum worlds

Recently, we proposed a new mechanism to generate a dc current of particles at zero bias based on a noble interplay between coherence and decoherence [S. W. Kim and M-S. Choi, Phys. Rev. Lett. 95, 226802 (2005)]. We showed that a dc current arises if the transport process in one direction is coherent while the process in the opposite direction is incoherent. Related issues such as the first and the second law of thermodynamics, the law of detailed balances, and the validity of the plane wave description, will be discussed in detail.