  It has long been an ultimate goal to introduce chemical doping at the atomic
level to precisely tune properties of materials. Two-dimensional materials have
natural advantage because of its highly-exposed surface atoms, however, it is
still a grand challenge to achieve this goal experimentally. Here, we
demonstrate the ability to introduce chemical doping in graphene with
atomic-level precision by controlling chemical adsorption of individual Se
atoms, which are extracted from the underneath WSe2, at the interface of
graphene-WSe2 heterostructures. Our scanning tunneling microscopy (STM)
measurements, combined with first-principles calculations, reveal that
individual Se atoms can chemisorbed on three possible positions in graphene,
which generate distinct pseudospin-mediated atomic-scale vortices in graphene.
We demonstrate that the chemisorbed positions of individual Se atoms can be
manipulated by STM tip, which enables us to achieve atomic-scale controlling
quantum interference of the pseudospin-mediated vortices in graphene. This
result offers the promise of controlling properties of materials through
chemical doping with atomic-level precision.
