End-State-Controlled Quantum Transport in Armchair Graphene Nanoribbon Artificial Quantum Materials
Artificial quantum materials based on atomically precise graphene nanostructures provide an ideal platform for exploring quantum phenomena arising from localized electronic states. Here, we develop a real-space theoretical framework to elucidate the microscopic origin of interface states in graphene architectures composed of $n$-triangulenes and armchair graphene nanoribbons (AGNRs). By continuously tuning the coupling between graphene building blocks, we reveal the evolution of triangulene zero-energy modes and AGNR end states into compact localized node orbitals at three-arm junctions. For the chiral bipartite junctions considered here, the number and sublattice character of these node orbitals follow a general counting relation, $N_{node,δ}=|N_{es,t,A(B)}-N_{tri,0,B(A)}|$, where $N_{es,t}$ is the total number of AGNR end states contributed by the three AGNR arms and $N_{tri,0}$ is the number of triangulene zero-energy modes. The resulting node-orbital chirality is determined by the dominant constituent: when $N_{es,t}>N_{tri,0}$, they inherit the sublattice chirality of the AGNR end states ($δ=A(B)$), whereas for $N_{tri,0}>N_{es,t}$ they inherit that of the triangulene zero-energy modes ($δ=B(A)$). Using experimentally synthesized triangulene nanographenes as representative examples, we further identify their low-energy zero-mode structure and investigate its manifestation in tunneling transport within an extended Anderson framework. Finally, we demonstrate that these node orbitals can serve as elementary building blocks for constructing artificial graphene nanoribbons with highly tunable flat subbands near the Fermi energy. The resulting compact localized states exhibit controllable degeneracy and strongly anisotropic quantum transport.