Artificial Graphene Nanoribbons: A Test Bed for Topology and Low-Dimensional Dirac Physics

We synthesize artificial graphene nanoribbons by positioning
carbon
monoxide molecules on a copper surface to confine its surface state
electrons into artificial atoms positioned to emulate the low-energy
electronic structure of graphene derivatives. We demonstrate that
the dimensionality of artificial graphene can be reduced to one dimension
with proper “edge” passivation, with the emergence of
an effectively gapped one-dimensional nanoribbon structure. These
one-dimensional structures show evidence of topological effects analogous
to graphene nanoribbons. Guided by first-principles calculations,
we spatially explore robust, zero-dimensional topological states by
altering the topological invariants of quasi-one-dimensional artificial
graphene nanostructures. The robustness and flexibility of our platform
allow us to toggle the topological invariants between trivial and
nontrivial on the same nanostructure. Ultimately, we spatially manipulate
the states to understand fundamental coupling between adjacent topological
states that are finely engineered and simulate complex Hamiltonians.