Kondo Chains of Organic Radicals on Metallic Surfaces: A Model System of Heavy Fermion Quantum Criticality
En Li, Bimla Danu, Yufeng Liu, Huilin Xie, Zhangyu Yuan, Can Li, Yashi Jiang, Jacky W. Y. Lam, Ben Zhong Tang, Shiyong Wang, Fakher F. Assaad, Nian Lin
Abstract
The spin chains made of organic open-shell radicals represent a platform to explore quantum magnetism. Here we provide an experimental realization of such systems in terms of organic radicals using on-surface synthesis on a Au(111) surface. The spatially resolved differential conductance spectra reveal that the ground state of the organic radicals is a Kramer's doublet that can be modeled by a spin 1/2 degree of freedom, which is entangled with the conduction electrons of the substrate. We find that the spin-spin exchange interactions between the neighboring radicals and the spin-substrate Kondo interaction are competing, resulting in emergent many-body Kondo physics. Using quantum Monte Carlo simulations, we show that a Kondo lattice model of spin chains on a metallic surface accurately reproduces the experimental results. This allows us to interpret experimental results in terms of a Kondo lattice at the quantum critical point. We foresee that the tunability of these systems will pave the way for realizing quantum simulators of heavy Fermion criticality.