Lateral electron tunneling through single self-assembled InAs quantum dots coupled to superconducting nanogap electrodes

Shibata, K.; Buizert, C.; Oiwa, A.; Hirakawa, K.; Tarucha, S.

Lateral electron tunneling through single self-assembled InAs quantum dots coupled to superconducting nanogap electrodes

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Description

We have fabricated superconductor-quantum dot-superconductor (SC-QD-SC) junctions by using SC aluminum electrodes with narrow gaps laterally contacting a single self-assembled InAs QD. The fabricated junctions exhibited clear Coulomb staircases and Coulomb oscillations at 40 mK. Furthermore, clear suppression in conductance was observed for the source-drain voltage $|V_{\rm SD}| < 2Δ/e$, where $Δ$ is the SC energy gap of Al. The absence of Josephson current that flows through QDs is due to the strong Coulomb interaction and non-negligible thermal fluctuation in our measurement system.