Kondo Insulators Modeled by the One Dimensional Anderson Lattice: A Numerical Renormalization Group Study

TL;DR

This study uses numerical renormalization group methods to analyze one-dimensional Anderson lattices, revealing how charge and spin gaps vary with interaction strength and how RKKY interactions differ between symmetric and asymmetric cases.

Contribution

It provides a detailed numerical analysis of Kondo insulators modeled by the Anderson lattice, highlighting the effects of asymmetry and interaction strength on electronic properties.

Findings

Charge gap exceeds spin gap for all U values.

RKKY interactions are prominent in symmetric cases at large U.

Asymmetry suppresses RKKY interactions, aligning with experimental observations.

Abstract

In order to better understand Kondo insulators, we have studied both the symmetric and asymmetric Anderson lattices at half-filling in one dimension using the density matrix formulation of the numerical renormalization group. We have calculated the charge gap, spin gap and quasiparticle gap as a function of the repulsive interaction U using open boundary conditions for lattices as large as 24 sites. We find that the charge gap is larger than the spin gap for all U for both the symmetric and asymmetric cases. RKKY interactions are evident in the f-spin-f-spin correlation functions at large U in the symmetric case, but are suppressed in the asymmetric case as the f-level approaches the Fermi energy. This suppression can also be seen in the staggered susceptibility and it is consistent with neutron scattering measurements in CeNiSn.