Kondo effect in defect-bound quantum dots coupled to NbSe2

We report the fabrication of a van der Waals tunneling device hosting a defect-bound quantum dot coupled to NbSe2. We find that upon application of a magnetic field, the device exhibits a zero-bias conductance peak. The peak, which splits at higher fields, is associated with a Kondo effect. At the same time, the junction retains conventional quasiparticle tunneling features at finite bias. Such coexistence of a superconducting gap and a Kondo effect are unusual, and are explained by noting the two-gap nature of the superconducting state of NbSe2, where a magnetic field suppresses the low-energy gap associated with the Se band. Our data shows that van der Waals architectures, and defect-bound dots in them, can serve as an effective platform for investigating the interplay of Kondo screening and superconducting pairing in unconventional superconductors.