Janus graphene nanoribbons with localized states on a single zigzag edge

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

doi:10.1038/s41586-024-08296-x

Janus graphene nanoribbons with localized states on a single zigzag edge

Nature. 2025 Jan 8. doi: 10.1038/s41586-024-08296-x. Online ahead of print.

Authors

Shaotang Song^#¹, Yu Teng^#^{1

2}, Weichen Tang^#^{3

4}, Zhen Xu^#⁵, Yuanyuan He¹, Jiawei Ruan^{3

4}, Takahiro Kojima⁵, Wenping Hu^{2

6}, Franz J Giessibl⁷, Hiroshi Sakaguchi⁸, Steven G Louie^{9

10}, Jiong Lu¹¹

Affiliations

¹ Department of Chemistry, National University of Singapore, Singapore, Singapore.
² Joint School of National University of Singapore and Tianjin University, International Campus of Tianjin University, Fuzhou, China.
³ Department of Physics, University of California, Berkeley, Berkeley, CA, USA.
⁴ Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA.
⁵ Institute of Advanced Energy, Kyoto University, Kyoto, Japan.
⁶ Tianjin Key Laboratory of Molecular Optoelectronics, Department of Chemistry, School of Science, Tianjin University, Tianjin, China.
⁷ Institute of Experimental and Applied Physics, University of Regensburg, Regensburg, Germany.
⁸ Institute of Advanced Energy, Kyoto University, Kyoto, Japan. [email protected].
⁹ Department of Physics, University of California, Berkeley, Berkeley, CA, USA. [email protected].
¹⁰ Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA. [email protected].
¹¹ Department of Chemistry, National University of Singapore, Singapore, Singapore. [email protected].

^# Contributed equally.

PMID: 39779862
DOI: 10.1038/s41586-024-08296-x

Abstract

Topological design of π electrons in zigzag-edged graphene nanoribbons (ZGNRs) leads to a wealth of magnetic quantum phenomena and exotic quantum phases^1-10. Symmetric ZGNRs typically show antiferromagnetically coupled spin-ordered edge states^1,2. Eliminating cross-edge magnetic coupling in ZGNRs not only enables the realization of a class of ferromagnetic quantum spin chains¹¹, enabling the exploration of quantum spin physics and entanglement of multiple qubits in the one-dimensional limit^3,12, but also establishes a long-sought-after carbon-based ferromagnetic transport channel, pivotal for ultimate scaling of GNR-based quantum electronics^1-3,9,13. 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^14-16, 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.