Breakdown of topological Thouless pumping in strongly interacting fermions

In 2016, experimentalists succeeded in demonstrating the realization of topological Thouless pumping using ultracold atoms. The topological Thouless pumping is characterized by the Chern number which gives the quantized pumped charge. Since the Chern number cannot be changed unless the energy gap collapses, the topological pumping of free fermions is considered to be stable at least against weak interactions. In this talk, however, we show that the topological Thouless pumping is forced to break down in a strongly correlated regime. This result is demonstrated using a spinful Rice-Mele model of repulsively interacting fermions. The key element for the breakdown of pumping is a crossover of a symmetry-protected topological phase from fermions to spin systems due to the increase of the Hubbard repulsion. Our result can be readily tested in current experimental setups.