Temperature dependence of Andreev spectra in a superconducting carbon nanotube quantum dot

TL;DR

This study investigates how temperature affects Andreev bound states in a superconducting carbon nanotube quantum dot, revealing thermal occupation effects and spectral inversions supported by theoretical modeling.

Contribution

It provides new experimental insights into temperature-dependent behavior of Andreev spectra in carbon nanotube quantum dots, supported by superconducting Anderson model calculations.

Findings

Observation of Andreev bound states within the superconducting gap

Detection of a weak replica due to quasi-particle tunneling

Inversion of ABS dispersion at higher temperatures

Abstract

Tunneling spectroscopy of a Nb coupled carbon nanotube quantum dot reveals the formation of pairs of Andreev bound states (ABS) within the superconducting gap. A weak replica of the lower ABS is found, which is generated by quasi-particle tunnelling from the ABS to the Al tunnel probe. An inversion of the ABS-dispersion is observed at elevated temperatures, which signals the thermal occupation of the upper ABS. Our experimental findings are well supported by model calculations based on the superconducting Anderson model.