Magneto-spin-orbit graphene: Chern topology and photoinduced Hall response

RESUMO

Magneto-spin-orbit graphene can host Chern phases due to proximity interactions, but in realistic heterostructures these depend on substrate chemistry, local stacking registry and may be altered by buried-interface reconstruction. Investigation of these effects requires special efforts to take into account the long-range moire patterns that often arise for these heterostructures. We address this question using first-principles calculations and effective four-band models for four out-of-plane magnetized Gr/(Au, Pt)/(Co, Mn) heterostructures in commensurate (2 x 2) and moire (9 x 9) supercells where the latter include misfit dislocations for the Co-based interfaces. The commensurate cells overestimate charge transfer and exaggerate valley asymmetry, whereas moire averaging strongly reduces both effects while preserving sizable spin splittings. The Pt spacer mediates stronger proximity interactions than Au, while replacing Co by Mn substantially changes the balance of the effective exchange interactions in a spacer-dependent manner. Introduction of misfit dislocations into the Co-based structures is selective and tunes the Dirac gap in Gr/Au/Co or spin splittings in Gr/Pt/Co. Graphene in Gr/Pt/Co exhibits effective ferromagnetic Chern phase with C = 2 in all studied supercells. By contrast, the moire models of the other three compositions are ferrimagnetic and topologically trivial, with C = 0. Nevertheless, they exhibit helicity-dependent photoinduced Hall responses, which are strongly enhanced by misfit-dislocation reconstruction in Gr/Au/Co. This work demonstrates that moire-scale stacking controls the effective Chern phase and Hall conductivity, whereas buried-interface defects tune the photoinduced Hall response without changing the topology.