Tunable Kondo resonance at a pristine two-dimensional Dirac semimetal on a Kondo insulator

TL;DR

This study demonstrates the emergence of a tunable Kondo resonance in graphene when interfaced with a Kondo insulator, revealing a many-body ground state and hybridization effects at the interface.

Contribution

It reports the first observation of Kondo resonance in graphene induced by proximity to a Kondo insulator, tunable by temperature and charge density.

Findings

Kondo resonance observed in graphene on SmB6

Hybridization of Dirac fermions with Sm 4f states

Kondo screening enhanced with cooling and doping

Abstract

Proximity of two different materials leads to an intricate coupling of quasiparticles so that an unprecedented electronic state is often realized at the interface. Here, we demonstrate a resonance-type many-body ground state in graphene, a non-magnetic two-dimensional Dirac semimetal, when grown on SmB6, a Kondo insulator, via thermal decomposition of fullerene molecules. This ground state is typically observed in three-dimensional magnetic materials with correlated electrons. Above the characteristic Kondo temperature of the substrate, the electron band structure of pristine graphene remains almost intact. As temperature decreases, however, the Dirac fermions of graphene become hybridized with the Sm 4f states. Remarkable enhancement of the hybridization and Kondo resonance is observed with further cooling and increasing charge carrier density of graphene, evidencing the Kondo screening of the Sm 4f local magnetic moment by the conduction electrons of graphene at the interface. These findings manifest the realization of the Kondo effect in graphene by the proximity of SmB6 that is tuned by temperature and charge carrier density of graphene.