Chaos in quantum ratchets

In systems with broken spatial symmetry, directed transport of particles can be observed in the absence of any time-averaged forces or gradients, if the system is kept away from thermal equilibrium. The underlying principle of such "ratchets" has found applications in particle separation and in the modelling of molecular motors in living systems, and has also attracted much interest from a fundamental point of view. In particular, chaos in classical ratchets, and quantum effects such as tunnelling, have each been found to have a strong effect on direction and magnitude of the particle current. Here we are interested in the question how classically chaotic ratchets would behave in the quantum regime. Can chaotic behaviour be observed in quantum ratchets, or, alternatively, could ratchet effects be generated from quantum chaotic behaviour. From the point of view of experimentalists, we discuss these questions with a focus on mesoscopic electron devices, and point to possible topics for theoretical investigations.