Artificial heavy fermions in a van der Waals heterostructure

TL;DR

This paper demonstrates the creation of artificial heavy fermions in a van der Waals heterostructure, enabling exploration of strongly correlated quantum phenomena in a tunable 2D platform.

Contribution

It introduces a novel van der Waals heterostructure that exhibits artificial heavy fermions through engineered Kondo coupling, a significant advancement over traditional rare-earth-based systems.

Findings

Observation of Kondo effect in heterostructure

Detection of heavy-fermion hybridization gap

Tunable electronic properties via stacking order

Abstract

Heavy fermion systems represent one of the paradigmatic strongly correlated states of matter. They have been used as a platform for investigating exotic behavior ranging from quantum criticality and non-Fermi liquid behavior to unconventional topological superconductivity. Heavy fermions arise from the exchange interaction between localized magnetic moments and conduction electrons that leads to the well-known Kondo effect. In a Kondo lattice, the interaction between the localized moments gives rise to a band with heavy effective mass. This intriguing phenomenology has so far only been realized in compounds containing rare-earth elements with 4f or 5f electrons. Here, we realize a designer van der Waals heterostructure where artificial heavy fermions emerge from the Kondo coupling between a lattice of localized magnetic moments and itinerant electrons in a 1T/1H-TaS$_2$ heterostructure. We study the heterostructure using scanning tunneling microscopy (STM) and spectroscopy (STS) and show that depending on the stacking order of the monolayers, we can either reveal the localized magnetic moments and the associated Kondo effect, or the conduction electrons with a heavy-fermion hybridization gap. Our experiments realize an ultimately tuneable platform for future experiments probing enhanced many-body correlations, dimensional tuning of quantum criticality, and unconventional superconductivity in two-dimensional artificial heavy-fermion systems.