Realization of Kagome Kondo lattice

TL;DR

This paper reports the experimental realization of a Kagome Kondo lattice in CsCr6Sb6, revealing heavy fermions, Kondo insulating behavior, and layer-dependent magnetic order, thus opening new avenues for studying quantum criticality in frustrated systems.

Contribution

First experimental realization of Kagome Kondo lattice with detailed electronic and magnetic properties, demonstrating heavy fermions and layer-dependent magnetism.

Findings

Observation of heavy fermions with effective mass over 100 times greater

Detection of Kondo insulating behavior at ultra-low carrier density

Layer-dependent magnetic order transitioning from bulk to few layers

Abstract

The Kondo lattice, describing a grid of the local magnetic moments coupling to itinerant electrons, is a fertile ground of strongly correlated states in condensed matter physics. While the Kagome lattice has long been predicted to host Kondo physics with exotic magnetism and nontrivial topology, no experimental realization has been achieved. Here, we report the discovery of CsCr6Sb6, a van der Waals-like Kagome Kondo lattice featuring extremely flat, isolated bands at the Fermi level (EF) that composed entirely of Cr-3d electrons. We observe heavy fermions with the effective mass over 100 times greater than those of its vanadium counterpart. We also observe Kondo insulating behavior in an ultra-low carrier density of 1019 cm-3 and dimensionality-induced Kondo breakdown. More interestingly, the frustrated magnetism observed in the bulk give way to a hidden A-type antiferromagnetic ordering in few layers, in sharp contrast to the common sense of weakened magnetism with thinning. The realization of Kondo physics in Kagome lattice opens avenues for exploring diverse quantum criticalities in a strongly-correlated frustrated system.