Imaging Friedel oscillations in rhombohedral trilayer graphene

Abstract

Quasiparticle interference-induced spatial standing waves in local density of states, i.e., Friedel oscillations, are first visualized in rhombohedral trilayer graphene (rTG) by using scanning tunneling microscopy and spectroscopy. We show that the long-range standing-wave patterns of rTG can be created not only by the scattering off usual potential barriers including defects and step edges, but also by ABC-ABA stacking domain walls. For step edges as scatterers, both the surface step edge and the underlying step edge can effectively generate quasiparticle standing waves on the surface layer. For all observed types of scatterers in rTG, the Friedel oscillations always exhibit a $1/r$ spatial decay. This decay rate of Friedel oscillations is consistent with that in bilayer graphene, while slower than that in monolayer graphene, directly confirming previous theoretical predictions. Our results provide fundamental knowledge of the nature of scatterers in rTG, which would help us to better understand their microscopic scattering mechanisms.