Sub-gap spectroscopy of thermally excited quasiparticles in a Nb contacted carbon nanotube quantum dot

Abstract

We present electronic transport measurements of a single wall carbon nanotube quantum dot coupled to Nb superconducting contacts. For temperatures comparable to the superconducting gap peculiar transport features are observed inside the Coulomb blockade and superconducting energy gap regions. The observed temperature dependence can be explained in terms of sequential tunneling processes involving thermally excited quasiparticles. In particular, these new channels give rise to two unusual conductance peaks at zero bias in the vicinity of the charge degeneracy point and allow to determine the degeneracy of the ground states involved in transport. The measurements are in good agreement with model calculations.

arXiv comment5 pages, 4 figures

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• Subgap resonant quasiparticle transport in normal-superconductor quantum dot devices
• Thermally induced subgap features in the cotunneling spectroscopy of a carbon nanotube
• Transmission of a microwave cavity coupled to localized Shiba states
• A particle conserving approach to AC-DC driven interacting quantum dots with superconducting leads