posted on 2020-03-04, 18:36authored byJames Lawrence, Pedro Brandimarte, Alejandro Berdonces-Layunta, Mohammed S. G. Mohammed, Abhishek Grewal, Christopher C. Leon, Daniel Sánchez-Portal, Dimas G. de Oteyza
We
extensively characterize the electronic structure of ultranarrow
graphene nanoribbons (GNRs) with armchair edges and zigzag termini
that have five carbon atoms across their width (5-AGNRs), as synthesized
on Au(111). Scanning tunneling spectroscopy measurements on the ribbons,
recorded on both the metallic substrate and a decoupling NaCl layer,
show well-defined dispersive bands and in-gap states. In combination
with theoretical calculations, we show how these in-gap states are
topological in nature and localized at the zigzag termini of the nanoribbons.
In addition to rationalizing the driving force behind the topological
class selection of 5-AGNRs, we also uncover the length-dependent behavior
of these end states which transition from singly occupied spin-split
states to a closed-shell form as the ribbons become shorter. Finally,
we demonstrate the magnetic character of the end states via transport experiments in a model two-terminal device structure in
which the ribbons are suspended between the scanning probe and the
substrate that both act as leads.