Nonequilibrium fractional Hall response after a topological quench

We theoretically study the Hall response of a lattice system following a quench where the topology of a filled band is suddenly changed. In the limit where the physics is dominated by a single Dirac cone, we find that the change in the Hall conductivity is two-thirds of the quantum of conductivity. We explore this universal behavior in the Haldane model and discuss cold-atom experiments for its observation. Beyond the linear response, the Hall effect crosses over from fractional to integer values. We investigate finite-size effects and the role of harmonic confinement.