Spectroscopy of $NbS{e}_2$ using Energy-Tunable Defect-Embedded Quantum Dots

Abstract

Quantum dots have sharply defined energy levels, which can be used for high resolution energy spectroscopy when integrated in tunneling circuitry. Here we report dot-assisted spectroscopy measurements of the superconductor $NbS{e}_2$, using a van der Waals device consisting of a vertical stack of $graphene-Mo{S}_2-NbS{e}_2$. The $Mo{S}_2$ tunnel barriers host naturally occurring defects which function as quantum dots, allowing transport via resonant tunneling. The dot energies are tuned by an electric field exerted by a back-gate, which penetrates the graphene source electrode. Scanning the dot potential across the superconductor Fermi energy, we reproduce the $NbS{e}_2$ density of states which exhibits a well-resolved two-gap spectrum. Surprisingly, we find that the dot-assisted current is dominated by the lower energy feature of the two $NbS{e}_2$ gaps, possibly due to a selection rule which favors coupling between the dots and the orbitals which exhibit this gap.

arXiv comment22 pages, 6 figures

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Cited by in corpus (11)

• Spin-valley locking for in-gap quantum dots in a MoS2 transistor
• Non-Destructive Low-Temperature Contacts to MoS2 Nanoribbon and Nanotube Quantum Dots
• Nonlocal measurement of quasiparticle charge and energy relaxation in proximitized semiconductor nanowires using quantum dots
• Spin-filtered measurements of Andreev bound states
• Reduced absorption due to defect-localized interlayer excitons in transition metal dichalcogenide-graphene heterostructures
• Effects of 3 MeV Proton Irradiation on Superconductivity and CDW in 2H-NbSe2 Single Crystals
• A magnetically-induced Coulomb gap in graphene due to electron-electron interactions
• Imaging the Sub-Moiré Potential Landscape using an Atomic Single Electron Transistor
• Charge quenching at defect states in transition metal dichalcogenide-graphene van der Waals heterobilayers
• Kondo Effect in Defect-bound Quantum Dots Coupled to NbSe${}_2$
• Origin of subgap states in normal-insulator-superconductor van der Waals heterostructures