Artificially built Kondo chains with organic radicals on metallic surfaces: new model system of heavy fermion quantum criticality

TL;DR

This paper reports the creation of organic radical chains on metallic surfaces as a new experimental platform to study heavy fermion quantum criticality, combining STM techniques and quantum simulations.

Contribution

It introduces a novel model system of organic radical chains on metal surfaces to investigate heavy fermion quantum criticality, bridging experimental realization and theoretical modeling.

Findings

Site-dependent low-energy excitations observed via STM

Quantum Monte Carlo simulations match experimental data

System demonstrates heavy fermion behavior below coherence temperature

Abstract

Heavy fermion quantum criticality is an extremely rich domain of research which represents a framework to understand strange metals as a consequence of a Kondo breakdown transition. Here we provide an experimental realization of such systems in terms of organic radicals on a metallic surface. The ground state of organic radicals is a Kramer's doublet that can be modeled by a spin 1/2 degree of freedom. Using on-surface synthesis and scanning tunneling microscopy (STM) tip manipulation, one can controllably engineer and characterize chains of organic radicals on a Au(111) surface. The spatial-resolved differential conductance reveals site-dependent low-energy excitations, which support the picture of emergent many-body Kondo physics. Using quantum Monte Carlo simulations, we show that a Kondo lattice model of spin chains on a metallic surface reproduces accurately the experimental results. This allows us to interpret the experimental results in terms of a heavy fermion metal, below the coherence temperature. We foresee that the tunability of these systems will pave the way to realize quantum simulators of heavy fermion criticality.