  The interplay between spontaneous symmetry breaking in many-body systems, the
wavelike nature of quantum particles and lattice effects produces an
extraordinary behavior of the chiral current of bosonic particles in the
presence of a uniform magnetic flux defined on a two-leg ladder. While
non-interacting as well as strongly interacting particles, stirred by the
magnetic field, circulate along the system's boundary in the counterclockwise
direction in the ground state, interactions stabilize vortex lattices. These
states break translational symmetry, which can lead to a reversal of the
circulation direction. Our predictions could readily be accessed in quantum gas
experiments with existing setups or in arrays of Josephson junctions.
