Multiband Fractional Thouless Pumps

Quantization of particle transport lies at the heart of topological physics. In Thouless pumps-dimensionally reduced versions of the integer quantum Hall effect-quantization is dictated by the integer winding of single-band Wannier states. Here, we show that repulsive interactions can drive a transition from an integer- to a fractional-quantized Thouless pump (at fixed integer filling) by stabilizing a crystal of multiband Wannier states, each with fractional winding. We numerically illustrate the concept in few-particle systems and show that a dynamical Hartree-Fock ansatz can quantitatively reproduce the pumping phase diagram.