Photoinduced anomalous Hall effect in the interacting Haldane model: Targeting topological states with pump pulses

Abstract

We investigate the nonequilibrium dynamics of the spinless Haldane model with nearest-neighbor interactions on the honeycomb lattice by employing an unbiased numerical method. In this system, a first-order transition from the Chern insulator at weak coupling to the charge-density-wave (CDW) phase at strong coupling can be characterized by a level crossing of the lowest energy levels. Here we show that if adiabatically following the eigenstates across this level crossing, their Chern numbers are preserved, leading to the identification of a topologically nontrivial low-energy excited state in the CDW regime. By promoting a resonant energy excitation via an ultrafast circularly polarized pump pulse, we find that the system acquires a nonvanishing Hall response as a result of the large overlap enhancement between the time-dependent wave function and the topologically nontrivial excited state. This response is suggestive of a photoinduced topological phase transition via unitary dynamics, despite a proper definition of the Chern number remaining elusive for an out-of-equilibrium interacting system. We contrast these results with more common quench protocols in which such features are largely absent in the dynamics even if the postquench Hamiltonian displays a topologically nontrivial ground state.

Topics & Concepts