近日，新加坡国立大学的Jiong Lu与美国加州大学的Steven G. Louie等人合作并取得一项新进展。经过不懈努力，他们实现了单之字形边缘局域态的Janus石墨烯纳米带。相关研究成果已于2025年1月8日在国际权威学术期刊《自然》上发表。

该研究团队报道了一种通用方法，用于设计和制造具有两种不同边缘构型的雅努斯石墨烯纳米带（JGNRs），以实现此类铁磁性石墨烯纳米带。在Lieb定理和拓扑分类理论的指导下，研究人员通过不对称地在一条之字形边缘引入苯基序列拓扑缺陷阵列，同时保持另一条之字形边缘不变，设计出了两种JGNRs。这打破了结构对称性，并在每个晶胞内产生了子晶格失衡，从而引发了自旋对称性破缺。

研究人员设计了三种Z形前驱体，用于制造一条母本之字形石墨烯纳米带和两条具有最优缺陷阵列晶格间距的JGNRs，以完全猝灭“缺陷”边缘的磁性边缘态。扫描探针显微镜和光谱学表征以及第一性原理密度泛函理论计算证实，研究人员成功制造了JGNRs，其铁磁基态沿未受干扰的之字形边缘局域。

据悉，之字形边缘石墨烯纳米带（ZGNRs）中π电子的拓扑设计引发了丰富的磁性量子现象和奇异的量子相。对称的ZGNRs通常表现出反铁磁耦合的自旋有序边缘态。消除ZGNRs中的跨边缘磁耦合，不仅能够实现一类铁磁量子自旋链，从而在一维极限下探索量子自旋物理和多个量子比特的纠缠，而且还建立了长期以来备受追捧的碳基铁磁传输通道，这对于基于GNR的量子电子器件的最终定标至关重要。

附：英文原文

Title: Janus graphene nanoribbons with localized states on a single zigzag edge

Author: Song, Shaotang, Teng, Yu, Tang, Weichen, Xu, Zhen, He, Yuanyuan, Ruan, Jiawei, Kojima, Takahiro, Hu, Wenping, Giessibl, Franz J., Sakaguchi, Hiroshi, Louie, Steven G., Lu, Jiong

Issue&Volume: 2025-01-08

Abstract: Topological design of π electrons in zigzag-edged graphene nanoribbons (ZGNRs) leads to a wealth of magnetic quantum phenomena and exotic quantum phases. Symmetric ZGNRs typically show antiferromagnetically coupled spin-ordered edge states. Eliminating cross-edge magnetic coupling in ZGNRs not only enables the realization of a class of ferromagnetic quantum spin chains, enabling the exploration of quantum spin physics and entanglement of multiple qubits in the one-dimensional limit, but also establishes a long-sought-after carbon-based ferromagnetic transport channel, pivotal for ultimate scaling of GNR-based quantum electronics. Here we report a general approach for designing and fabricating such ferromagnetic GNRs in the form of Janus GNRs (JGNRs) with two distinct edge configurations. Guided by Lieb’s theorem and topological classification theory, we devised two JGNRs by asymmetrically introducing a topological defect array of benzene motifs to one zigzag edge, while keeping the opposing zigzag edge unchanged. This breaks the structural symmetry and creates a sublattice imbalance within each unit cell, initiating a spin-symmetry breaking. Three Z-shaped precursors are designed to fabricate one parent ZGNR and two JGNRs with an optimal lattice spacing of the defect array for a complete quench of the magnetic edge states at the ‘defective’ edge. Characterization by scanning probe microscopy and spectroscopy and first-principles density functional theory confirms the successful fabrication of JGNRs with a ferromagnetic ground-state localized along the pristine zigzag edge.

DOI: 10.1038/s41586-024-08296-x

Source: https://www.nature.com/articles/s41586-024-08296-x