Topological pumping induced by spatiotemporal modulation of interaction

Particle-particle interaction provides a new degree of freedom to induce novel topological phenomena. Here, we propose to use spatiotemporal modulation of interaction to realize topological pumping without single-particle counterpart. Because the modulation breaks time-reversal symmetry, the multiparticle energy bands of bound states have none-zero Chern number, and support topological bound edge states. In a Thouless pump, a bound state that uniformly occupies a topological energy band can be shifted by integer unit cells per cycle, consistent with the corresponding Chern number. We can also realize topological pumping of bound edge state from one end to another. The entanglement entropy between particles rapidly increases at transition points, which is related to the spatial spread of a bounded pair. In addition, we propose to realize hybridized pumping with fractional displacement per cycle by adding an extra tilt potential to separate topological pumping of the bound state and Bloch oscillations of single particle. Our work could trigger further studies of correlated topological phenomena that do not have a single-particle counterpart.