Quantum Interferences of Pseudospin-Mediated Atomic-Scale Vortices in Monolayer Graphene.

A vortex is a universal and significant phenomenon that has been known for centuries. However, creating vortices to the atomic limit has remained elusive. Very recently, it was demonstrated that intervalley scattering induced by the single carbon defect of graphene leads to phase winding over a closed path surrounding the defect. Motivated by this, we demonstrate that the single carbon defects at A and B sublattices of graphene can be regarded as pseudospin-mediated atomic-scale vortices with angular momenta l = +2 and -2, respectively. The quantum interference measurements of the vortices indicate that the vortices cancel each other, resulting in zero total angular momentum, in the |A| = |B| case, and they show aggregate chirality and angular momenta similar to a single vortex of the majority in the |A| ≠ |B| case, where |A| (|B|) is the number of vortices with angular momenta l = +2 (l = -2).