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.
Bibliographical noteFunding Information:
Devices for this study were fabricated at the Center for Nanoscience and Nanotechnology, The Hebrew University. Funding for this work was provided by a European Research Council Starting Grant (No. 637298, TUNNEL), Israel Science Foundation Grant No. 861/19, and BSF Grant No. 2016320. E.R. thanks the Aspen Center for Physics, which is supported by National Science Foundation Grant No. PHY-1607611, where part of this work was conducted, and Kevin Ingersent for very helpful discussions.
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