Kondo screening regimes in multi-Dirac and Weyl systems

TL;DR

This paper explores how magnetic impurities are screened in multi-Dirac and Weyl systems, revealing complex regimes influenced by symmetry breaking and chemical potential, with implications for understanding Kondo physics in topological materials.

Contribution

It provides a comprehensive numerical analysis of Kondo screening in multi-Dirac and Weyl systems, highlighting new regimes and effects of symmetry breaking on Kondo behavior.

Findings

Kondo screening exists in single-, double-, and triple-Dirac/Weyl systems.

Symmetry breaking and chemical potential significantly influence Kondo temperature.

Double- and triple-Weyl systems exhibit richer Kondo regimes than single-Weyl systems.

Abstract

We have investigated the Kondo physics of a single magnetic impurity embedded in multi-Dirac (Weyl) node fermionic systems. By using a generic effective model for the host material and employing a numerical renormalization group approach we access the low temperature behavior of the system, identifying the existence of Kondo screening in single-, double-, and triple-Dirac (Weyl) node models. We find that in any multi-Dirac node systems the low-energy regime lies within one of the known classes of pseudogap Kondo problem, extensively studied in the literature. Kondo screening is also observed for time reversal symmetry broken Weyl systems. This is, however, possible only in the particle-hole symmetry broken regime obtained for finite chemical potential $\mu$. Although weakly, breaking time-reversal symmetry suppresses the Kondo resonance, especially in the single-node Weyl semimetals. More interesting Kondo screening regimes are obtained for inversion symmetry broken multi-Weyl fermions. In these systems the Kondo regimes of double- and triple-Weyl node models are much richer than in the single-Weyl node model. While in the single-Weyl node model the Kondo temperature increases monotonically with $|\mu|$ regardless the value of the inversion symmetry breaking parameter $Q_0$, in double- and triple-Weyl node models there are two distinct regimes: (i) For $Q_0< |\mu|$ the Kondo temperature depends strongly on $\mu$, while (ii) for $Q_0 > |\mu|$ the Kondo temperature depends very weakly on $\mu$, resembling the flat-band single impurity Anderson model.