Current reversals and current suppression in an open two-degree-of-freedom system.

We explore the scattering of particles evolving in a two-degree-of-freedom Hamiltonian system, in which both degrees of freedom are open. Particles, initially having all kinetic energy, are sent into a so-called "interaction region," where there will be an exchange of energy with particles that are initially at rest. The open nature of both components of this system eliminates any restrictions on which particles can escape from the interaction region. Notably, it is shown that two particles can cooperate in a mutual exchange of energy allowing both particles to escape and travel large distances. It is also shown that this level of cooperation is highly sensitive to the coupling strength between both components of the system. Indeed, large fluctuations of the magnitude and direction of the current are observed for small changes of this coupling parameter. Further, it is seen that current reversals are a prominent feature of this model. Another interesting observation is that even with the presence of chaotic scattering, it is possible that the system, for certain parameter regimes, will express a vanishing current, suggesting that there is a restoration of symmetry which, due to the initial setup, is broken. For an explanation of the different features of particle motion, we relate the phase-space dynamics to the various regimes of particle current.