Environmental effects on layer-dependent dynamics of Dirac fermions in quasicrystalline bilayer graphene

The carrier dynamics in various types of epitaxial graphene layers on SiC substrates was investigated by means of time- and angle-resolved photoemission spectroscopy (TARPES). Layer-dependent electron doping was observed in the Dirac bands of quasicrystalline bilayer graphene after optical pumping, leading to generation of transient voltage between the upper and lower layers. The amount of photoinduced carrier transport depends on the distance from the substrate. A comparison of the TARPES results of single-layer graphene between flat and stepped SiC substrates experimentally indicates that a source of the doping carriers likely originates from interface step states. The dynamic model is described based on the electronic structure, calculated using density functional theory.