Quantum spin liquid in an RKKY-coupled two-impurity Kondo system

TL;DR

This paper demonstrates the emergence of a quantum spin liquid phase in a two-impurity Kondo system driven by RKKY interactions, revealing complex phase transitions and potential realizations in heavy-fermion materials.

Contribution

It provides a detailed numerical analysis of the phase diagram of a two-impurity Kondo system, highlighting the conditions for stabilizing a quantum spin liquid without geometric frustration.

Findings

Identification of a metallic spin-liquid phase stabilized by strong intraband correlations.

Discovery of two quantum phase transitions separating spin liquid and Kondo singlet phases.

Observation of an RKKY spin-dimer phase and a crossover at critical coupling.

Abstract

We consider a 2-impurity Kondo system with spin-exchange coupling within the conduction band. Our numerical renormalization group calculations show that for strong intraband spin correlations the competition of these correlations with Kondo spin screening stabilizes a metallic spin-liquid phase of the localized spins without geometric frustration. For weak Kondo coupling the spin liquid and the Kondo singlet phase are separated by two quantum phase transitions and an intermediate RKKY spin-dimer phase, while beyond a critical coupling they are connected by a crossover. The results suggest how a quantum spin liquid may be realized in heavy-fermion systems near a spin-density wave instability.