Kavli Affiliate: Michael F. Crommie
| First 5 Authors: Michael C. Daugherty, Peter H. Jacobse, Jingwei Jiang, Joaquim Jornet-Somoza, Reis Dorit
| Summary:
The integration of low-energy states into bottom-up engineered graphene
nanoribbons (GNRs) is a robust strategy for realizing materials with tailored
electronic band structure for nanoelectronics. Low-energy zero-modes (ZMs) can
be introduced into nanographenes (NGs) by creating an imbalance between the two
sublattices of graphene. This phenomenon is exemplified by the family of
[n]triangulenes. Here, we demonstrate the synthesis of [3]triangulene-GNRs, a
regioregular one-dimensional (1D) chain of [3]triangulenes linked by
five-membered rings. Hybridization between ZMs on adjacent [3]triangulenes
leads to the emergence of a narrow band gap, Eg = 0.7 eV, and topological end
states that are experimentally verified using scanning tunneling spectroscopy
(STS). Tight-binding and first-principles density functional theory (DFT)
calculations within the local spin density approximation (LSDA) corroborate our
experimental observations. Our synthetic design takes advantage of a selective
on-surface head-to-tail coupling of monomer building blocks enabling the
regioselective synthesis of [3]triangulene-GNRs. Detailed ab initio theory
provides insight into the mechanism of on-surface radical polymerization,
revealing the pivotal role of Au-C bond formation/breakage in driving
selectivity.
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