Length-Independent Quantum Transport through Engineered Band States in Graphene Nanoribbon Junctions

Abstract

In molecular electronics, the development of molecular wires capable of carrying high electrical current with minimal loss remains a central challenge, despite extensive efforts in both solution-phase and ultrahigh-vacuum synthesis. Graphene nanoribbons (GNRs) with their structural robustness and tunable electronic properties have emerged as promising candidates. In particular, topologically engineered GNRs with atomically precise edge modifications offer new routes for efficient charge transport. Here, we systematically investigate the transport properties of a staggered, edge-extended GNR based on a 7-AGNR backbone, denoted as 7-AGNR-S(1,3), using low-temperature scanning tunneling microscopy liftoff experiments. Under favorable junction conditions, the conductance remains nearly constant during tip retraction over junction lengths exceeding 10 nm, mediated by the low-energy bands arising from the coupled topological zero-energy edge states. Additionally, we developed a detailed model of the liftoff process and simulated charge transport, revealing the roles of delocalized valence band states and showing how local potential variations at the electrode interfaces can modulate molecular-level alignment and conductance. Our findings underscore the importance of interface engineering in the design of high-performance molecular electronic devices.