The JGNR, designed with a ferromagnetic edge state confined to one edge, allows for the creation of a one-dimensional ferromagnetic spin chain. Such a configuration is essential for applications in spintronics and the assembly of multi-qubit systems, foundational elements in quantum computing. The team, led by Associate Professor Lu Jiong from the NUS Department of Chemistry, collaborated with international experts, including Professor Steven G Louie of UC Berkeley and Professor Hiroshi Sakaguchi of Kyoto University.
Graphene nanoribbons are narrow carbon structures with extraordinary magnetic properties stemming from unpaired electrons in their atomic p-orbitals. By engineering their edge structures into a precise zigzag pattern, researchers created a one-dimensional spin-polarised channel. This feature could revolutionize spintronic devices and enable next-generation quantum computing technologies.
The term "Janus", derived from the two-faced Roman god symbolizing duality, reflects the dual nature of the JGNR's properties. In this groundbreaking material, only one edge of the ribbon adopts a zigzag configuration, a world-first in creating a one-dimensional ferromagnetic carbon chain. This achievement was made possible by designing Z-shaped molecular precursors that ensure precise control over the ribbon's atomic structure.
"Magnetic graphene nanoribbons, which are narrow strips of graphene formed by fused benzene rings, offer tremendous potential for quantum technologies due to their long spin coherence times and the potential to operate at room temperature. Creating a one-dimensional single zigzag edge in such systems is a daunting yet essential task for realising the bottom-up assembly of multiple spin qubits for quantum technologies," explained Assoc Prof Lu.
The synthesis of JGNRs involved a meticulous two-step process. First, researchers created Z-shaped molecular precursors through conventional solution-based chemistry. These precursors were then employed in on-surface synthesis, a solid-phase chemical reaction conducted in ultra-clean environments. This approach enabled precise atomic-level control over the graphene's structural features.
The Z-shaped design facilitated asymmetric fabrication, allowing independent modification of one branch while preserving the integrity of the zigzag edge. Researchers also adjusted the length of the modified branch to control the JGNR's width. State-of-the-art scanning probe microscopy and density functional theory analyses confirmed the successful production of JGNRs with a ferromagnetic ground state confined to the single zigzag edge.
"The rational design and on-surface synthesis of a novel class of JGNR represent a conceptual and experimental breakthrough for realising one-dimensional ferromagnetic chain. Creating such JGNRs not only expands the possibilities for precise engineering of exotic quantum magnetism and enables the assembly of robust spin arrays as new-generation qubits. Furthermore, it enables the fabrication of one-dimensional spin-polarised transport channels with tunable bandgaps, which could advance carbon-based spintronics at the one-dimensional limit," added Assoc Prof Lu.
The study detailing this advancement was published in the journal Nature on January 9, 2025.
Research Report:Janus graphene nanoribbons with localized states on a single zigzag edge
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