Non-Fermi liquid behavior and quantum criticality in cubic heavy fermion systems with non-Kramers multipolar local moments

TL;DR

This paper explores quantum criticality and non-Fermi liquid behavior in cubic heavy fermion systems with non-Kramers multipolar moments, using a Bose-Fermi Kondo model and renormalization group analysis to identify critical points and phase transitions.

Contribution

It introduces a theoretical framework for understanding quantum critical points in multipolar heavy fermion systems via a two-loop RG analysis of the Bose-Fermi Kondo model.

Findings

Identification of critical points between non-Fermi liquid and quadrupolar ordered phases.

Prediction of measurable higher order octupolar susceptibility near criticality.

Expansion of known phase diagram for multipolar heavy fermion systems.

Abstract

Notable non-Fermi liquid and quantum critical behaviors are observed in rare-earth metallic systems with non-Kramers local moments supporting a number of different multipolar moments. A prominent example is $\text{Pr(Ti,V)}_{2}\text{Al}_{20}$, where the non-Kramers doublet of the $\text{Pr}^{3+}$ ion allows quadrupolar and octupolar moments, but lacks a dipolar moment. Previous theoretical studies show that a single impurity Kondo problem with such an unusual local moment leads to novel non-Fermi liquid states. In this work, we investigate possible quantum critical behaviors arising from the competition between non-Fermi liquid states and multipolar-ordered phases induced by the RKKY interaction. We consider a local version of the corresponding Kondo lattice model, namely the Bose-Fermi Kondo model. Here, the multipolar local moments are coupled to fermionic and bosonic bath degrees of freedom representing the multipolar Kondo effect and RKKY interactions. Using a perturbative renormalization group (RG) study up to two loop order, we find critical points between non-Fermi liquid Kondo fixed points and a quadrupolar ordered fixed point. The critical points describe quantum critical behaviors at the corresponding phase transitions and can be distinguished by higher order corrections in the octupolar susceptibility that can be measured by ultrasound experiments. Our results imply the existence of a rich expansion of the phases and quantum critical behaviors in multipolar heavy fermion systems.