Global Phase Diagram and Momentum Distribution of Single-Particle Excitations in Kondo insulators

TL;DR

This paper maps the phase diagram of a frustrated Kondo lattice model, revealing various magnetic and metallic phases, and analyzes how single-particle excitations evolve, providing insights into pressure-induced transitions in Kondo insulators.

Contribution

It presents a comprehensive theoretical phase diagram for a frustrated Kondo lattice, including Kondo-destroyed phases and Fermi-surface precursors, advancing understanding of pressure effects in Kondo insulators.

Findings

Identification of multiple zero-temperature phases including Kondo-insulator and magnetic metals.

Demonstration of Fermi-surface-like features as precursors to metallic states.

Theoretical explanation of pressure-induced gap closing in Kondo insulators.

Abstract

Kondo insulators are emerging as a simplified setting to study both magnetic and metal-to-insulator quantum phase transitions. Here, we study a half-filled Kondo lattice model defined on a magnetically frustrated Shastry-Sutherland geometry. We determine a "global" phase diagram that features a variety of zero-temperature phases; these include Kondo-destroyed antiferromagnetic and paramagnetic metallic phases in addition to the Kondo-insulator phase. Our result provides the theoretical basis for understanding how applying pressure to a Kondo insulator can close its hybridization gap, liberate the local-moment spins from the conduction electrons, and lead to a magnetically correlated metal. We also study the momentum distribution of the single-particle excitations in the Kondo insulating state, and illustrate how Fermi-surface-like features emerge as a precursor to the actual Fermi surfaces of the Kondo-destroyed metals. We discuss the implications of our results for Kondo insulators including SmB$_6$.