Photoinduced dc Hall current in few-layer black phosphorus with a gate-tunable Floquet gap

We theoretically explore Floquet engineering in few-layer black phosphorus (fBP) under time-periodic driving. Motivated by the ability of circularly polarized light to induce nontrivial topological states at Dirac nodes, we investigate the emergence of a photoinduced dc Hall effect in the Dirac semimetal phase of fBP. Starting from a low-energy continuum model, we derive the effective Floquet Hamiltonian and analytically calculate the Berry curvature, demonstrating the opening of a topological gap. We also perform lattice-model calculations incorporating a self-consistent Hartree method to compute Floquet band structures and dc Hall conductivity under a perpendicular electric field. Our results reveal that the dc Hall current in fBP can be effectively tuned via a periodic driving field and electrostatic gating.