Magneto-optical conductivity of epitaxial graphene modulated by external fields

We theoretically investigate the magneto-optical transport properties of epitaxial graphene subjected to a perpendicular magnetic field combined with substrate-induced electric and antiferromagnetic exchange fields, as well as illumination by circularly polarized light. Substrate-driven symmetry breaking opens a finite Dirac gap and generates a nontrivial Berry curvature, leading to electronic and optical responses that are distinct from those of pristine graphene. We calculate the non-equidistant Landau-level spectrum characteristic of Dirac fermions and analyze the density of states and Berry curvature to resolve spin- and valley-dependent topological features. We show that the interplay of external perturbations stabilizes multiple topological phases, including quantum valley Hall, quantum anomalous Hall, quantum spin–valley Hall, and hybrid phases. Distinct magneto-optical signatures of these phases are identified in the longitudinal and optical Hall conductivities through inter-Landau-level transitions, underscoring their potential for tunable optoelectronic and spintronic applications in two-dimensional quantum materials.