The Thouless pump quantizes charge transport: as a periodic potential is adiabatically cycled, exactly one electron is transported per cycle — protected by topology (Chern number = 1).
The Rice-Mele model: H = Σ[t(1+δcos φ)(c†ᵢcᵢ₊₁+h.c.) + Δ sin φ · nᵢ]. As φ sweeps 0→2π adiabatically, the spectral flow threads energy levels through the gap. The Chern number C=1 guarantees exactly one quantum of charge pumped per cycle — a topological invariant immune to disorder. This is the quantum analogue of an Archimedes' screw.