Kondo screening and Magnetism at Interfaces

TL;DR

This study models metal-insulator interfaces to explore how hybridization influences magnetic and electronic properties, revealing a complex interplay between Kondo physics and magnetic order across layers.

Contribution

It introduces a multi-layer tight-binding model to analyze the evolution of magnetism and conductivity at interfaces, highlighting the competition between antiferromagnetism and Kondo singlet formation.

Findings

Kondo insulating phase emerges at intermediate hybridization.

Magnetic order is suppressed at the interface but restored in other layers.

Residual Kondo effects reduce magnetic order near the interface.

Abstract

The nature of magnetic order and transport properties near surfaces is a topic of great current interest. Here we model metal-insulator interfaces with a multi-layer system governed by a tight-binding Hamiltonian in which the interaction is non-zero on one set of adjacent planes and zero on another. As the interface hybridization is tuned, magnetic and metallic properties undergo an evolution that reflects the competition between anti-ferromagnetism and (Kondo) singlet formation in a scenario similar to that occurring in heavy-fermion materials. For a few-layer system at intermediate hybridization, a Kondo insulating phase results where magnetic order and conductivity are suppressed in all layers. As more insulating layers are added, magnetic order is restored in all correlated layers except that at the interface. Residual signs of Kondo physics are however evident in the bulk as a substantial reduction of the order parameter in the 2-3 layers immediately adjacent to the interfacial one. We find no signature of long range magnetic order in the metallic