EP-like degeneracies splitting dynamics induced in strongly correlated materials by Floquet engineering

Nontrivial band structure topology can be induced through time-periodic fields via Floquet engineering. Here, using time-dependent density functional theory, we demonstrate that above-bandgap circularly polarized photoexcitations induce the formation and splitting of exceptional point (EP)-like degeneracies in the strongly correlated material NiO. The polarization-selective splitting sequence of upper (UEP-like) and lower (LEP-like) EP-like degeneracies reveals laser-driven phase transitions. Spin fluctuations under polarization switching confirm the annihilation of the z-spin component and emergence of tunable x–y plane spin component, indicating that ultrafast demagnetization generates in-plane spin reorientation. Concurrently, the time-dependent reduction in the orbital-effective Hubbard U and many-body energy evolution demonstrate a transition of electrons from localized to itinerant states. This work establishes the strongly correlated insulator NiO as a distinctive platform for light–matter coupling. Crucially, we demonstrate that resonant above-gap excitation is an essential prerequisite for dynamical control, which not only reveals photon energy as a decisive parameter for steering non-Hermitian phenomena but also enables the controlled transition from an insulating state to metallicity.