Designing Long and Highly Conducting Molecular Wires with Multiple Nontrivial Topological States

Molecular one-dimensional topological insulators (1DTIs), describedby the Su-Schrieffer-Heeger (SSH) model, are a new classof molecular electronic wires whose low-energy topological edge statesendow them with high electrical conductivity. However, when these1D TIs become long, the high conductance is not sustained becausethe coupling between the edge states decreases with increasing length.Here, we present a new design where we connect multiple short 1D SSHTI units linearly or in a cycle to create molecular wires with a continuoustopological state density. Using a tight-binding method, we show thatthe linear system gives a length-independent conductance. The cyclicsystems show an interesting odd-even effect, with unit transmissionin the topological limit, but zero transmission in the trivial limit.Furthermore, based on our calculations, we predict that these systemscan support resonant transmission with a quantum of conductance. Wecan further expand these results to phenylene-based linear and cyclic1D TI systems and confirm the length-dependent conductance in suchsystems.

Automated summary

In this study, a new design is presented where multiple short one-dimensional topological insulator (1DTI) units are connected linearly or cyclically to create molecular wires with continuous topological state density. Using tight-binding methods, it is shown that the conductance of the linear system is independent of length, while the cyclic systems exhibit an interesting odd-even effect. Based on calculations, resonant transmission with a quantum of conductance is predicted for these systems. These findings are further extended to phenylene-based linear and cyclic 1DTI systems, confirming the length-dependent conductance in such systems.