Enhanced charge fluctuations due to competitions between intersite and Kondo-Yosida singlet formations in heavy-fermion systems

TL;DR

This study explores how charge fluctuations in heavy-fermion systems are significantly enhanced due to the competition between intersite and Kondo-Yosida singlet formations, especially near critical points and crossover regimes.

Contribution

It demonstrates the enhancement of charge fluctuations caused by competing singlet states using the two-impurity Anderson model and numerical renormalization group analysis.

Findings

Charge susceptibility diverges logarithmically at the critical point with particle-hole symmetry.

Charge fluctuations are strongly enhanced near the crossover between Kondo-Yosida and intersite singlet states.

Enhanced charge fluctuations may explain increased residual resistivity in heavy-fermion compounds under pressure.

Abstract

We investigate f-electron charge susceptibility in a two-impurity Anderson model on the basis of Wilson's numerical renormalization group method. The f-electron charge susceptibility diverges logarithmically at the critical point of this model when conduction-electron bands exhibit particle-hole symmetry. Although the critical point disappears without the particle-hole symmetry, the f-electron charge fluctuation is much more enhanced near the crossover regime between the Kondo-Yosida singlet and intersite spin-singlet states than that in the single-impurity case. This result shows that charge fluctuations are enhanced owing to the competition between intersite and Kondo-Yosida spin singlets. A possible scenario for the enhanced residual resistivity near the region where the Kondo temperature becomes comparable with the N\'eel temperatures under pressure in some heavy-fermion compounds is proposed.