Tailoring topological order and {\pi}-conjugation to engineer quasi-metallic polymers

TL;DR

This paper demonstrates how designing and synthesizing specific 1D { extbackslash pi}-conjugated polymers can induce topological phase transitions, resulting in quasi-metallic behavior with edge states, advancing the control of topological properties in organic materials.

Contribution

It introduces a novel design strategy for 1D { extbackslash pi}-conjugated polymers to achieve topological phase transitions and quasi-metallic states through on-surface synthesis.

Findings

Polymer design can induce topological phase transitions.

Narrow bandgap with zero-energy edge states observed.

Fundamental link between topology and electronic structure established.

Abstract

Topological band theory provides a conceptual framework to predict or even engineer robust metallic states at the boundaries of topologically distinct phases. The bulk-boundary correspondence requires that a topological electronic phase transition between two insulators must proceed via closing of the electronic gap. Therefore, it can provide a conceptual solution to the instability of metallic phases in {\pi}-conjugated 1D polymers. In this work we predict and demonstrate that a clever design and on-surface synthesis of polymers consisting of 1D linearly bridged polyacene moieties, can position the resulting polymer near the topological transition from a trivial to a non-trivial quantum phase featuring a very narrow bandgap with in-gap zero-energy edge-states at the topologically non-trivial phase. We also reveal the fundamental connection between topological classes and electronic transformation of 1D {\pi}-conjugated polymers.