  Layers of twisted bilayer graphene exhibit varieties of exotic quantum
phenomena1-5. Today, the twist angle {\Theta} has become an important degree of
freedom for exploring novel states of matters, i.e. two-dimensional
superconductivity ( {\Theta} = 1.1{\deg})6, 7 and a two-dimensional
quasicrystal ({\Theta} = 30{\deg})8, 9. We report herein experimental
observation on the photo-induced ultrafast dynamics of Dirac fermions in the
quasicrystalline 30{\deg} twisted bilayer graphene (QCTBG). We discover that
hot carriers are asymmetrically distributed between the two graphene layers,
followed by the opposing femtosecond relaxations, by using time- and
angle-resolved photoemission spectroscopy. The key mechanism involves the
differing carrier transport between layers and the transient doping from the
substrate interface. The ultrafast dynamics scheme continues after the Umklapp
scattering, which is induced by the incommensurate interlayer stacking of the
quasi-crystallinity. The dynamics in the atomic layer opens the possibility of
new applications and creates interdisciplinary links in the optoelectronics of
van der Waals crystals.
