Quantum manipulation of molecular radical spins provides a crucial platform for exploring emergent phenomena in many-body systems. Here, we combine surface-confined synthesis with scanning tunneling microscopy(STM)tip-induced dehydrogenation to achieve atom-precise engineering of quasi-one-dimensional porphyrin-based Kondo chains (1-7 units) on Au(111). High-resolution STS measurements and low-energy effective modeling collectively demonstrate that {\pi}-radicals at each fused-porphyrin unit form Kondo singlets screened by conduction electrons. Adjacent singlets develop direct coherent coupling via quantum-state-overlap-enabled electron tunneling. Crucially, chiral symmetry in the effective model governs zero-mode distribution-present in odd-length chains yet absent in even-length chains-which dictates pronounced odd-even quantum effects in STS spectra of finite chains. Furthermore, the number of parallel porphyrin chains non-monotonically tunes the competition between the Kondo effect and spin exchange, showing opposing trends in strength and demonstrating that both wave-function overlap and the SOMO-LUMO gap collectively govern these interactions. This work simultaneously resolves the dimensional dependence of many-body correlations in confined quantum systems and pioneers approaches for quantum-critical manipulation in molecular spin architectures.
@article{arxiv.2506.10729,
title = {Construction of Kondo Chains by Engineering Porphyrin {\pi}-Radicals on Au(111)},
author = {Yan Zhao and Kaiyue Jiang and Peng-Yi Liu and Jie Li and Ruoning Li and Xin Li and Xinchen Fang and Anjing Zhao and Yutong Zhu and Hongxiang Xu and Ting Chen and Dong Wang and Xiaodong Zhuang and Shimin Hou and Kai Wu and Song Gao and Qing-Feng Sun and Yajie Zhang and Yongfeng Wang},
journal= {arXiv preprint arXiv:2506.10729},
year = {2025}
}