Spatial inversion symmetry breaking of vortex current in a biased-ladder superfluid

We investigate the quench dynamics of interacting bosons on a two-leg ladder in the presence of a uniform Abelian gauge field. The model hosts a variety of emergent quantum phases, and we focus on the superfluid biased-ladder phase breaking the Z2 symmetry of two legs. We observe an asymmetric spreading of vortex current and particle density, i.e., the vortices propagate ballistically on the right and dissolve during the propagation on the left, indicating spontaneous breaking of the spatial inversion symmetry. By decreasing the repulsion strength, it is found that the ballistic propagating vortices are more robust than the dissolving ones on the other side.