  We study the effect of an applied magnetic field on the nonequilibrium
transport properties of a general cubic quantum network described by a
tight-binding Hamiltonian with specially designed couplings to the leads that
preserve open-system symmetries. We demonstrate that the symmetry of open
systems can be manipulated by the direction of the magnetic field. Starting
with all the symmetries preserved in absence of a field, the anisotropic and
isotropic fields systematically break the symmetries, influencing all
nonequilibrium properties. For simple cubic systems, we are able to identify
the steady states that comprise of pure states, bath-dependent states
(nonequilibrium steady states), and also nonphysical states. As an application,
we show numerically for large cubic networks that the symmetry breaking can
control nonequilibrium currents and that different environmental interactions
can lead to novel features which can be engineered in artificial super-lattices
and cold atoms.
