Theory of Charge Kondo Effect on Pair Hopping Mechanism

TL;DR

This paper introduces a microscopic model for the charge Kondo effect driven by pair hopping interactions, revealing the coexistence of charge and spin Kondo-Yosida singlets and their impact on electronic properties.

Contribution

It proposes a new microscopic model for the charge Kondo effect based on pair hopping, analyzed through numerical renormalization group methods.

Findings

Charge Kondo effect arises from pair hopping interactions.

Coexistence of charge and spin Kondo-Yosida singlets observed.

Enhanced Sommerfeld coefficient due to singlet competition.

Abstract

A new microscopic model of the charge Kondo effect is proposed, and is studied on the basis of a numerical renormalization group calculations. It is shown that the charge Kondo effect is caused by a pair hopping interaction between the conduction band and the localized band. It is found that the formation of a charge Kondo-Yosida singlet due to its mechanism corresponds to the appearance of valence skipping phenomenon, and that the charge Kondo-Yosida singlet and the spin Kondo-Yosida singlet state coexist for a tuned parameter set, because the charge and spin degrees of freedom are separated in this model. Then, it is also found that the Sommerfeld coefficient is enhanced by the competition between these two singlet states.