Competition between Kondo and RKKY correlations in the presence of strong randomness

TL;DR

This paper investigates how strong randomness influences the competition between Kondo and RKKY interactions in heavy fermion systems, revealing a new quantum criticality universality class with a phase transition between spin liquid and Fermi liquid states.

Contribution

It introduces an effective local field theory for disordered Anderson lattice models, showing how randomness affects hybridization and RKKY interactions, leading to novel quantum phase transitions.

Findings

Disorder induces a phase transition from spin liquid to Fermi liquid.

Holon condensation vanishes in the clean limit but becomes finite with strong hybridization variance.

The phase diagram reveals a transition controlled by the relative variance of hybridization and RKKY interactions.

Abstract

We propose that competition between Kondo and magnetic correlations results in a novel universality class for heavy fermion quantum criticality in the presence of strong randomness. Starting from an Anderson lattice model with disorder, we derive an effective local field theory in the dynamical mean-field theory (DMFT) approximation, where randomness is introduced into both hybridization and Ruderman-Kittel-Kasuya-Yosida (RKKY) interactions. Performing the saddle-point analysis in the U(1) slave-boson representation, we reveal its phase diagram which shows a quantum phase transition from a spin liquid state to a local Fermi liquid phase. In contrast with the clean limit of the Anderson lattice model, the effective hybridization given by holon condensation turns out to vanish, resulting from the zero mean value of the hybridization coupling constant. However, we show that the holon density becomes finite when variance of hybridization is sufficiently larger than that of the RKKY coupling, giving rise to the Kondo effect. On the other hand, when the variance of hybridization becomes smaller than that of the RKKY coupling, the Kondo effect disappears, resulting in a fully symmetric paramagnetic state, adiabatically connected with the spin liquid state of the disordered Heisenberg model. ......