Building spin-1/2 antiferromagnetic Heisenberg chains with diaza-nanographenes
New publication in Nature Synthesis.
An international research team reported the precise synthesis of spin-1/2 Heisenberg antiferromagnetic chains using diaza-hexa-peri-hexabenzocoronene (diaza-HBC) units. This study provides a comprehensive analysis of the magnetic properties of finite spin chains, uncovering a distinct odd-even dependence.
The development of quantum magnets in nanomaterials is of central interest due to their potential applications in emerging quantum technologies. Graphene nanostructures featuring spin-polarized π-electrons serve as an ideal model system for investigating the nature of correlated spins in one-dimensional (1D) system. Among various quantum magnetic systems, 1D quantum spin chains represent a particularly significant class. In recent years, substantial progress has been made in realizing 1D quantum spin chains through the topological design of π-electron networks, achieved via the on-surface synthesis of graphene-based nanostructures with atomic precision, enabled by scanning tunneling microscopy and spectroscopy (STM/STS). Notably, S = 1 antiferromagnetic chains based on non-Kekulé triangulene units have been synthesized on surfaces, exhibiting a topological Haldane spin chain phase. However, realizing S = 1/2 antiferromagnetic Heisenberg chains—another fundamental model for investigating correlated magnetism—has remained challenging due to the lack of appropriate molecular building blocks and efficient synthetic strategies.
Scientists from the Max Planck Institute of Microstructure Physics and Technische Universität Dresden, in collaboration with partners, successfully demonstrated the on-surface synthesis of spin-1/2 antiferromagnetic Heisenberg chains with parity-dependent magnetization, utilizing diaza-hexa-peri-hexabenzocoronene (diaza-HBC) units, where two distinct precursors and synthetic pathways with varied terminations were employed. Electron donation from each diaza-HBC core to the Au(111) substrate led to the emergence of a robust odd–even effect in spin coupling along the chain, where even-numbered chains exhibited gapped excitations, whereas odd-numbered chains displayed Kondo resonance in their odd-numbered units. These results underscore the significant potential of 1D spin systems with intriguing quantum magnetism and pave the way for the development of quantum magnetic materials with applications in spintronics, and quantum computing. The results of this collaborative research have been recently published in Nature Synthesis.
