Topological quantum pump of strongly interacting fermions in coupled chains

We analyse a tight binding model of two coupled chains with strongly interacting fermions. Depending on the parameter w, the many body lowest energy band consists of either single particles or bound pairs. A topological quantum pump can be created by periodically varying the coupling strengths under adiabatic conditions. We numerically show that the single particles and bound pairs are pumped in opposite directions along topologically non-trivial paths. The exact quantization of the pumped charge can be expressed by a (many body) Chern number.