Discovery of an Antiferromagnetic Topological Nodal-line Kondo Semimetal

TL;DR

This paper reports the discovery of CeCo2P2, a topological Kondo lattice with antiferromagnetic order and a protected nodal line, revealing novel quantum phases from the interplay of topology, magnetism, and strong correlations.

Contribution

It introduces CeCo2P2 as the first known Kondo lattice with magnetic order in non-heavy electrons and a protected nodal line, expanding understanding of correlated topological materials.

Findings

CeCo2P2 exhibits coexistence of Kondo effect and antiferromagnetic order.

A topologically protected nodal line emerges near the Fermi energy at low temperatures.

The compound demonstrates unique interplay between itinerant and correlated electrons.

Abstract

The symbiosis of strong interactions, flat bands, topology and symmetry has led to the discovery of exotic phases of matter, including fractional Chern insulators, correlated moir\'e topological superconductors, and Dirac and Weyl semimetals. Correlated metals, such as those present in Kondo lattices, rely on the screening of local moments by a sea of non-magnetic conduction electrons. Here, we report on a unique topological Kondo lattice compound, CeCo2P2, where the Kondo effect - whose existence under the magnetic Co phase is protected by PT symmetry - coexists with antiferromagnetic order emerging from the flat bands associated with the Co atoms. Remarkably, this is the only known Kondo lattice compound where magnetic order occurs in non-heavy electrons, and puzzlingly, at a temperature significantly higher than that of the Kondo effect. Furthermore, at low temperatures, the emergence of the Kondo effect, in conjunction with a glide-mirror-z symmetry, results in a nodal line protected by bulk topology near the Fermi energy. These unusual properties, arising from the interplay between itinerant and correlated electrons from different constituent elements, lead to novel quantum phases beyond the celebrated topological Kondo insulators and Weyl Kondo semimetals. CeCo2P2 thus provides an ideal platform for investigating narrow bands, topology, magnetism, and the Kondo effect in strongly correlated electron systems.