# Kondo screening in a charge-insulating spinon metal

## TL;DR

This paper reports the first experimental observation of Kondo screening by chargeless spinon quasiparticles in a charge-insulating quantum spin liquid, revealing a new platform to study and manipulate exotic spin liquid states.

## Contribution

It demonstrates Kondo screening in a charge-insulating spin liquid, extending the concept beyond traditional metallic systems and providing a new way to probe spin liquids.

## Key findings

- Kondo effect observed with spinon excitations in a quantum spin liquid
- Spinon Fermi surface acts similarly to conduction electrons in Kondo screening
- Provides a new platform for studying spin liquid properties

## Abstract

The Kondo effect, an eminent manifestation of many-body physics in condensed matter, is traditionally explained as exchange scattering of conduction electrons on a spinful impurity in a metal. The resulting screening of the impurity's local moment by the electron Fermi sea is characterized by a Kondo temperature $T_K$, below which the system enters a non-perturbative strongly-coupled regime. In recent years, this effect has found its realizations beyond the bulk-metal paradigm in many other itinerant-electron systems, such as quantum dots in semiconductor heterostructures and in nanomaterials, quantum point contacts, and graphene. Here we report on the first experimental observation of the Kondo screening by chargeless quasiparticles. This occurs in a charge-insulating quantum spin liquid, where spinon excitations forming a Fermi surface take the role of conduction electrons. The observed impurity behaviour therefore bears a strong resemblance to the conventional case in a metal. The discovered spinon-based Kondo effect provides a prominent platform for characterising and possibly manipulating enigmatic host spin liquids.