The role of the short range magnetic correlations on the gap opening of the topological Kondo insulators

TL;DR

This study explores how short-range magnetic correlations influence the gap opening in topological Kondo insulators, revealing that antiferromagnetic correlations promote magnetic moments and Kondo effects, leading to various electronic phases including topological insulators.

Contribution

Introduces a modified periodic Anderson model with a narrow band to study magnetic correlations in Kondo topological insulators, highlighting their role in gap formation and phase transitions.

Findings

Short-range antiferromagnetic correlations favor magnetic moment formation.

Magnetic moments enable spin-flip scattering, contributing to the Kondo effect.

The phase diagram includes metallic, band insulator, and Kondo topological insulator phases.

Abstract

In this work we investigate the effects of the short range magnetic correlations on the gap opening of the topological Kondo insulators. We consider an additional narrow band to the otherwise completely localized f-electrons, by adding a term to the periodic Anderson model which allows a small hopping of the localized electrons between neighboring sites of the lattice. This new model is adequate to study a novel class of intermetallic 4f and 5f orbitals materials: the Kondo topological insulators, whose paradigmatic material is the compound SmB6. For simplicity, we consider a version of the periodic Anderson model on a two dimensional square lattice. The starting point of the model is the 4f-Ce ions orbitals, with J=5/2 multiplet in the presence of spin-orbit coupling. We present results of the correlation functions and we show that the short range antiferromagnetic correlations favors the formation of magnetic moments on the atoms, and at the same time the existence of these moments opens the possibility of the spin-flip scattering by the conduction electrons, generating the Kondo effect, which contribute to the opening of a gap in the density of states of the system. We also calculate the phase diagram which shows that, as we vary the Ef level position from the empty regime to the Kondo regime, the system develops several phases: metallic, band insulator and Kondo topological insulator. The band structure calculated shows that the model develops a strong topological insulator.