Kondo impurities in the Kitaev spin liquid: Numerical renormalization group solution and gauge-flux-driven screening

TL;DR

This paper investigates how magnetic impurities interact with the Kitaev spin liquid, revealing quantum phase transitions and flux-dependent screening using an exact numerical approach, advancing understanding of impurity behavior in topological quantum materials.

Contribution

It introduces a reformulation of the Kondo problem in the Kitaev model and provides a numerically exact solution highlighting flux-driven impurity screening and quantum phase transitions.

Findings

Impurity screening depends on gauge flux binding.

Quantum phase transitions occur with varying Kondo coupling.

Majorana fermions determine fixed-point impurity properties.

Abstract

Kitaev's honeycomb-lattice compass model describes a spin liquid with emergent fractionalized excitations. Here we study the physics of isolated magnetic impurities coupled to the Kitaev spin-liquid host. We reformulate this Kondo-type problem in terms of a many-state quantum impurity coupled to a multichannel bath of Majorana fermions and present the numerically exact solution using Wilson's numerical renormalization group technique. Quantum phase transitions occur as a function of Kondo coupling and locally applied field. At zero field, the impurity moment is partially screened only when it binds an emergent gauge flux, and otherwise becomes free at low temperatures. We show how Majorana degrees of freedom determine the fixed-point properties, make contact with Kondo screening in pseudogap Fermi systems, and discuss effects away from the dilute limit.