Behavior of the current in the asymmetric quantum multibaker map
  Recently, a new mechanism leading to purely quantum directed transport in the asymmetric multibaker map has been presented. Here, we show a comprehensive characterization of the finite asymptotic current behavior with respect to the $h$ value, the shape of the initial conditions, and the features of the spectrum. We have considered different degrees of asymmetry in these studies and we have also analyzed the classical and quantum phase space distributions for short times in order to understand the mechanisms behind the generation of the directed current. 
Leonardo Ermann, Gabriel G. Carlo and Marcos Saraceno