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

TL;DR

This paper demonstrates that ultrafast circularly polarized pump pulses can induce a transient topological Hall response in an interacting Haldane model, revealing a photoinduced topological phase transition through nonequilibrium dynamics.

Contribution

It shows that resonant pump pulses can generate a topologically nontrivial Hall response in an interacting system, highlighting a novel route to control topological states dynamically.

Findings

Photoinduced Hall response observed after resonant excitation.

Topologically nontrivial excited states identified in the CDW regime.

Contrast with quench protocols where topological features are absent.

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 (CI) 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 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 non-vanishing Hall response as a result of the large overlap enhancement between the time-dependent wave-function and the topologically non-trivial excited state. This 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, where such features are largely absent in the dynamics even if the post-quench Hamiltonian displays a topologically nontrivial ground state.