Subcycle videography of Landau–Zener–Majorana transitions in graphene

Abstract Strong light fields have unlocked entirely new possibilities to tailor coherent electron trajectories, engineer band structures and shape emergent phases of matter all-optically 1–9 . Unravelling the underlying quantum mechanisms requires a visualization of the lightwave-driven electron motion 10,11 directly in the band structure. Although photoelectron momentum microscopy has imaged photoexcited electrons averaged over many cycles of light 12–19 , subcycle band-structure videography has been limited to small electron momenta 8,20 . Yet, lightwave-driven elementary processes in quantum materials often occur throughout momentum space. Here we introduce attosecond-precision, subcycle band-structure videography covering the entire first Brillouin zone and visualize one of the most fundamental but elusive strong-field processes: non-adiabatic Landau–Zener–Majorana tunnelling. The interplay of strong-field-driven acceleration within the Dirac-like band structure of graphene and periodic Landau–Zener–Majorana interband tunnelling manifests in a coherent subcycle displacement and distortion of the carrier distribution at the Brillouin zone edge. The extremely non-thermal electron distributions also allow us to disentangle competing scattering processes and assess their impact on coherent electronic control. Our panoramic view of field-driven electron motion enables a new quality of microscopic understanding of strong-field control of quantum materials.