Kondo lattices with inequivalent local moments: Competitive vs. co-operative Kondo screening

TL;DR

This paper explores a Kondo lattice model with two distinct local moments, revealing how their interplay affects the phase diagram and low-temperature properties, especially when their screening temperatures differ significantly.

Contribution

It introduces a theoretical analysis of a two-sublattice Kondo lattice with different couplings, showing competition or cooperation between Kondo effects based on conduction band filling.

Findings

Two Kondo effects can either compete or cooperate depending on band filling.

Small differences in Kondo couplings can cause large variations in Kondo scales.

Proposes a connection between the studied model and depleted Kondo lattice systems.

Abstract

While standard heavy fermion metals feature a single spin-1/2 local moment per unit cell, more complicated systems with multiple distinct local moments have been synthesized as well, with Ce_3Pd_20(Si,Ge)_6 being one example. Here, we discuss the physics of a Kondo lattice model with two local-moment sublattices, coupled with different Kondo couplings to conduction electrons. The phase diagram will be strongly modified from that of the standard Kondo lattice if the characteristic screening temperatures of the distinct moments are well separated. Therefore, we investigate the interplay between the two Kondo effects using a local self-energy approximation via slave bosons. We find that the two Kondo effects can either compete or co-operate depending on the conduction-band filling. In the regime of competition, small differences in the two Kondo couplings can lead to huge differences in the respective Kondo scales, due to non-trivial many-body effects. We also study the low-temperature properties of the collective heavy Fermi-liquid state and propose a connection to depleted Kondo lattice systems.