Coherence scale of coupled Anderson impurities

TL;DR

This paper investigates the energy scales in coupled Anderson impurities, revealing a coherence scale that transitions from local moments to singlet states, influenced by RKKY interactions, akin to heavy fermion systems.

Contribution

It identifies and characterizes a coherence scale in coupled Anderson impurities, linking it to RKKY interactions and heavy fermion physics, which was not previously established.

Findings

High energy scale deviates from single-ion Kondo temperature

Scale is governed by RKKY interaction when dominant

Physical properties align with heavy fermion coherence scale

Abstract

For two coupled Anderson impurities, two energy scales are present to characterize the evolution from local moment state of the impurities to either of the inter-impurity singlet or the Kondo singlet ground states. The high energy scale is found to deviate from the single-ion Kondo temperature and rather scales as Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction when it becomes dominant. We find that the scaling behavior and the associated physical properties of this scale are consistent with those of a coherence scale defined in heavy fermion systems.