Rashba spin-orbit driven topological phase transitions in heterogeneous armchair honeycomb nanoribbons.

We investigate the emergence of nontrivial topological phases in heterogeneous armchair honeycomb nanoribbons arising from the interplay between structural geometry and Rashba spin-orbit coupling (RSOC). The system consists of a central RSOC-active region sandwiched between two pristine segments, forming interfaces between topologically distinct phases. As the RSOC strength increases, interface states emerge and become localized at the junctions. These states remain unchanged despite variations in edge configurations and ribbon widths. For finite ribbon widths, the RSOC induces a closing and subsequent reopening of the bulk energy gap, signaling a topological phase transition without altering the underlying lattice geometry. These findings reveal a route to engineering tunable topological states through the cooperative effects of interfacial structure and spin-orbit interactions.