Speaker
Description
Periodic driving of solids offers new opportunities for controlling and designing quantum phases of matter. Floquet engineering has, for example, been proposed as a route to induce topological states in graphene through circularly polarized light [1, 2] . However, the persistence of Floquet states under realistic conditions, including interactions, screening, and decoherence, remains an open question.
In this contribution, we explore extensions of the Floquet nonequilibrium Green's function formalism [3] aimed at describing driven materials beyond idealized settings. These developments enable the inclusion of electronic interactions, phonon scattering, and electromagnetic screening effects within a unified framework. The treatment of Coulomb interactions and electron--phonon coupling may, for instance, be formulated using self-energy approximations such as the second Born and Migdal approaches [4], while self-consistent coupling to Maxwell equations provides access to screening and feedback effects in driven systems [5].
Such extensions provide a foundation for assessing the realistic prospects of Floquet engineering in solids and for identifying regimes in which nonequilibrium phases may be stabilized. As a longer-term perspective, we discuss how this framework could be employed to investigate dynamical instabilities in periodically driven quantum materials [6].
[1] Oka et al. PRB 79, 081406(R) (2009)
[2] McIver et al. Nat. Phys. 16, 38–41 (2020)
[3] Tsuji et al., PRB 78 235124 (2008)
[4] Schüler et al. PRX 10 041013 (2020)
[5] Ong et al. arXiv:2504.00583 (2025)
[6] Okuwaga et al. arXiv:2601.04451 (206)