Modulated Kondo screening along magnetic mirror twin boundaries in monolayer MoS2

When a single electron is confined to an impurity state in a metal, a many-body resonance emerges at the Fermi energy if the electron bath screens the impurity’s magnetic moment. This is the Kondo effect, originally introduced to explain the abnormal resistivity behaviour in bulk magnetic alloys, and it has been realized in many quantum systems over the past decades, ranging from heavy-fermion lattices down to adsorbed single atoms. Here we describe a Kondo system that allows us to experimentally resolve the spectral function consisting of impurity levels and a Kondo resonance in a large Kondo temperature range, as well as their spatial modulation. Our approach is based on a discrete half-filled quantum confined state within a MoS2 grain boundary, which—in conjunction with numerical renormalization group calculations—enables us to test the predictive power of the Anderson model that is the basis of the microscopic understanding of Kondo physics. Interactions between a localized magnetic moment and electrons in a metal can produce an emergent resonance that affects the metal’s properties. A realization of this Kondo effect in MoS2 provides an opportunity to study it in microscopic detail.