▎ 摘　　要

Recently, the narrowest armchair graphene nanoribbon (AGNR) in the family of width n = 3p+2 has been fabricated [Kimouche et al., Nat. Commun. 6, 10177 (2015)]. Here, the effects of isolated pentagonal structures that are identified as the contacts of the formed AGNRs by monomers have been investigated. Our first principles results show that the coupling of pentagons dominates the transport properties of the junctions, i.e., a weak coupling enhances the conductance, remarkably higher than that of a perfect AGNR, whereas a strong coupling is opposite and the threshold voltage is not affected at all. Such a contrastive capacity implies the promotion of introducing isolated pentagons as a feasible technique to tune the transport properties of AGNR junctions. The underlying microscopic mechanisms are revealed for this technique. Published by AIP Publishing.