Designer Heavy Fermions in Incommensurate $\bf{Nb_3Cl_8}$/Graphene van der Waals Heterostructures

TL;DR

This paper presents a new method to engineer heavy fermions in van der Waals heterostructures by coupling a Mott insulator with graphene, enabling tunable correlated quantum phenomena without strict lattice matching.

Contribution

It introduces a general strategy for creating heavy fermions in incommensurate heterostructures, bypassing lattice-matching constraints and demonstrating tunable heavy fermion behavior.

Findings

Observation of a hybridization gap (~30 meV) indicating Kondo coherence.

Gate-tunable metal-insulator transition in the heterostructure.

Significant effective mass enhancement and magnetic field-induced transitions.

Abstract

Heavy fermion systems, traditionally realized in rare-earth compounds with limited tunability, have hindered systematic exploration of correlated quantum phenomena. Here, we introduce a general strategy for engineering heavy fermions in incommensurate van der Waals heterostructures by coupling a Mott insulator (Nb$_3$Cl$_8$) with itinerant electrons (from monolayer graphene), circumventing strict lattice-matching requirements. Through magnetotransport and slave spin mean-field calculations, we demonstrate the hybridization gap ($\Delta\approx30$ meV), gate-tunable metal-insulator transition, and band-selective electron effective mass enhancement, hallmarks of Kondo coherence. The heterostructure exhibits nearly order-of-magnitude electron effective mass dichotomy between hybridized and conventional graphene-like regimes, alongside in-plane magnetic field-induced metal-insulator transitions. Top gate-temperature phase mapping reveals competing correlated states, including insulating and hidden-order phases. This work establishes a scalable platform for designing heavy fermion by replacing the itinerant electron materials, with implications for engineering topological superconductivity and quantum criticality in low-dimensional systems.