Engineering of robust topological quantum phases in graphene nanoribbons

Abstract: Here we present a flexible strategy to realize robust nanomaterials exhibiting valence electronic structures whose fundamental physics is described by the SSH-Hamiltonian. These solid-state materials are realized using atomically precise graphene nanoribbons (GNR). We demonstrate the controlled periodic coupling of topological boundary states at junctions of armchair GNRs of different widths to create quasi-1D trivial and non-trivial electronic quantum phases. Their topological class is experimentally determined by drawing upon the bulk-boundary correspondence and measuring the presence (non-trivial) or absence (trivial) of localized end states by scanning tunneling spectroscopy (STS). The strategy we propose has the potential to tune the band width of the topological electronic bands close to the energy scale of proximity induced spin-orbit coupling or superconductivity, and may allow the realization of Kitaev like Hamiltonians and Majorana type end states.

• The paper presents a novel strategy to engineer robust topological phases in graphene nanoribbons using the Su-Schrieffer-Heeger model.
• It utilizes atomically precise on-surface synthesis and scanning tunneling spectroscopy to classify electronic states and confirm theoretical predictions with a bandwidth of 0.65 eV.
• The engineered nanoribbons exhibit structural stability under ambient conditions, indicating strong potential for spintronic devices and quantum computing applications.

Engineering of Robust Topological Quantum Phases in Graphene Nanoribbons

The research presented in "Engineering of Robust Topological Quantum Phases in Graphene Nanoribbons" addresses the realization of stable solid-state materials that exhibit topological quantum properties. The study successfully implements a strategy to engineer robust nanomaterials with electronic structures characterized by the Su-Schrieffer-Heeger (SSH) model using atomically precise graphene nanoribbons (GNRs). The key objective of this work is to tune electronic quantum phases and stabilize them such that they could find application in spintronic devices or as Qubits in quantum information technologies.

This paper showcases an advanced synthesis method, leveraging on-surface synthesis, to fabricate GNRs with precise atomic configurations. Notably, the authors design and synthesize GNR structures that encapsulate both trivial and non-trivial topological phases. By carefully controlling the periodic coupling of topological boundary states at junctions of armchair GNRs with variable widths, they achieve quasi-one-dimensional electronic phases whose properties adhere to the SSH Hamiltonian.

The unique experimental approach draws on bulk-boundary correspondence and scanning tunneling spectroscopy to classify these phases topologically, through the presence or absence of localized end states. One significant finding is the synthesis of staggered and inline edge-extended GNRs, particularly the 7-AGNR-[(1,3) structure, which demonstrates this technique's versatility and precision.

The paper reports that the experimentally observed bandwidth of 0.65(10) eV for the 7-AGNR-[(1,3) aligns well with tight-binding calculations, attesting to the reliability of the theoretical models employed. Additionally, the electronic and structural stability of these nanoribbons under ambient conditions fortifies the potential for practical implementation of these topological materials in nanoelectronics.

This work effectively paves the way for future developments in manipulating electronic states for topological quantum devices, suggesting that further tuning could yield significant enhancements in material functionalities. Future prospects include integrating these GNR-based topological phases in sophisticated electronic systems while exploring variations in coupling constants for further optimizations.

In essence, the successful realization of engineered topological quantum phases in GNRs presented in this study marks a substantial contribution to the effort of realizing stable and scalable quantum materials, thereby holding considerable promise for advancements in quantum computing and electronic applications.