Heavy quasiparticle bands in the underscreened quasiquartet Kondo lattice

TL;DR

This paper investigates the quasiparticle spectrum in an underscreened Kondo-lattice model with two CEF split doublets, revealing a new heavy band and hybridization gaps, and explores their dependence on model parameters.

Contribution

It introduces a three-band quasiparticle spectrum in a quasiquartet Kondo lattice model, highlighting a new heavy band and hybridization gaps influenced by CEF splitting.

Findings

Discovery of a new heavy quasiparticle band inside the hybridization gap.

Identification of multiple hybridization gaps influenced by CEF splitting.

Analysis of the dependence of Kondo scale and band widths on model parameters.

Abstract

We study the quasiparticle spectrum in an underscreened Kondo-lattice (KL) model that involves a single spin degenerate conduction band and two crystalline-electric-field (CEF) split Kramers doublets coupled by both orbital-diagonal and non-diagonal exchange interactions. We find the three quasiparticle bands of the model using a constrained fermionic mean field approach. While two bands are similar to the one-orbital model a new genuinely heavy band inside the main hybridization gap appears in the quasiquartet model. Its dispersion is due to effective hybridization with conduction states but the bandwidth is controled by the size of the CEF splitting. Furthermore several new indirect and direct hybridztion gaps may be identified. By solving the selfconsistency equation we calculate the CEF- splitting and exchange dependence of effective Kondo low energy scale, hybridization gaps and band widths. We also derive the quasiparticle spectral densities and their partial orbital contributions. We suggest that the two-orbital KL model can exhibit mixed CEF/Kondo excitonic magnetism.